Avid Bioservices Inc (CDMO)

[jazzbeerman]

slipperypete,

Today is the first mention of proof in humans that Bavituximab alters cytokines, - (less TGF-B, and more TNF-A), and that's a very important thing.

(It's exactly what I was hoping they'd mention.)


Maybe folks will get a little more out of these now that there is proof- in humans- that PS-blocking (with Bavituximab) alters immune response -


------------------------------------



Interaction between Phosphatidylserine and the Phosphatidylserine Receptor Inhibits Immune Responses In Vivo

http://www.jimmunol.org/cgi/content/full/174/3/1393


Peter R. Hoffmann2,*, Jennifer A. Kench*, Andrea Vondracek{dagger}, Ellen Kruk*, David L. Daleke{ddagger}, Michael Jordan{dagger}, Philippa Marrack{dagger}, Peter M. Henson* and Valerie A. Fadok*,{dagger}

The Journal of Immunology, 2005

.


Interaction between Phosphatidylserine and the Phosphatidylserine Receptor Inhibits Immune Responses In Vivo


Introduction

The rapid engulfment of apoptotic cells by professional and nonprofessional phagocytes prevents the release of potentially toxic or immunogenic intracellular contents from the dying cells (1, 2, 3, 4). Much attention has recently focused on the effects of apoptotic cells on phagocytes engulfing them. Interactions between macrophages and apoptotic cells result in the secretion of anti-inflammatory mediators such as TGF-{beta}, IL-10, and PGE2, as well as inhibition of the production of proinflammatory mediators (5, 6, 7, 8, 9, 10, 11). Similar results have been found with nonleukocytic phagocytes including fibroblasts and epithelial cells (Ref.12 ; J. Monks and V. A. Fadok, unpublished observations). In addition, apoptotic cells have been shown in some cases to inhibit dendritic cell maturation and Ag presentation (13, 14, 15).

Apoptotic cells have also been shown to affect inflammation and adaptive immune responses in vivo, although the results are conflicting. For example, apoptotic cells have been shown to be poor adjuvants compared with their necrotic counterparts in the generation of delayed-type hypersensitivity (15). Other evidence suggests that the uptake of apoptotic cells is not an immunologically null event, but is capable of modulating immune responses to self-Ags through induction of T cell-tolerance (16). The tolerizing effects of apoptotic cells have been further demonstrated in studies in which injection of apoptotic cells inhibited rejection of bone marrow allografts (17). By contrast, it has been suggested that apoptotic tumor cells can stimulate antitumor responses in vitro and possibly in vivo (18, 19, 20, 21).

Surprisingly, little is known regarding the mechanisms by which apoptotic cells inhibit inflammation and adaptive immune responses. Exposure of the anionic phospholipid phosphatidylserine (PS)3 in the outer leaflet of the plasma membrane is one of the most striking and consistent changes on the surface of apoptotic cells (22, 23, 24, 25, 26, 27, 28, 29). It has been known for some time that PS can inhibit macrophage production of proinflammatory cytokines and NO, and that it can block macrophage killing of intracellular parasites (30, 31, 32, 33, 34, 35, 36). Data derived from experiments in vitro and in vivo suggest that PS exposure is crucial for the release of TGF-{beta} by phagocytes that accompanies apoptotic cell recognition and uptake (11, 37, 38). Furthermore, PS-containing liposomes can mimic the response to apoptotic cells by generating TGF-{beta} release (11, 38). Blocking PS on apoptotic cells with annexin V (a Ca2+-dependent, PS-binding protein) has been shown to eliminate the inhibitory effects of the apoptotic cells on the humoral responses (39).

We hypothesized that PS exposed on apoptotic cells was a key factor in inhibiting the inflammatory response required for survival of Ag-specific T lymphocytes and subsequent activation of the adaptive immune response (40, 41). If this is true, PS should inhibit immune responses in vivo. Using three different immunogens and several different assays to measure immune responses, we determined that PS stereo-specifically inhibited responses of Ag-specific CD4+ T and B cells in vivo, and that these effects could be mimicked using an activating Ab directed against the PS receptor. Furthermore, these inhibitory effects could be reversed, at least in part, with anti-TGF-{beta} Ab, implicating TGF-{beta} as an important mediator of the inhibitory response to PS. PS-containing liposomes did not appear to block maturation of bone marrow-derived dendritic cells in response to bacterial endotoxin, TNF-{alpha}, or other stimuli as determined by alternation in expression of surface markers or by ability to present Ag to CD4+ lymphocytes. PS-containing liposomes also failed to block the Ag-induced migration of dendritic cells into regional lymph nodes in vivo. Taken together, these findings suggest that PS inhibits the immune response by inhibiting inflammation in tissue.








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REQUIRED READING #2 of 5 (abridged) ------





Phosphatidylserine Regulates the Maturation of Human Dendritic Cells



http://www.jimmunol.org/cgi/content/full/173/5/2985


The Journal of Immunology, 2004


Xiao Chen*, Kara Doffek*, Sonia L. Sugg{dagger} and Joel Shilyansky2,*
* Division of Pediatric Surgery and {dagger} Division of Endocrine Surgery, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI 53226





Phosphatidylserine Regulates the Maturation of Human Dendritic Cells


Phosphatidylserine (PS), which is exposed on the surface of apoptotic cells, has been implicated in immune regulation. However, the effects of PS on the maturation and function of dendritic cells (DCs), which play a central role in both immune activation and regulation, have not been described. Large unilamellar liposomes containing PS or phosphatidylcholine were used to model the plasma membrane phospholipid composition of apoptotic and live cells, respectively. PS liposomes inhibited the up-regulation of HLA-ABC, HLA-DR, CD80, CD86, CD40, and CD83, as well as the production of IL-12p70 by human DCs in response to LPS. PS did not affect DC viability directly but predisposed DCs to apoptosis in response to LPS. DCs exposed to PS had diminished capacity to stimulate allogeneic T cell proliferation and to activate IFN-{gamma}-producing CD4+ T cells. Exogenous IL-12 restored IFN-{gamma} production by CD4+ T cells. Furthermore, activated CTLs proliferated poorly to cognate Ag presented by DCs exposed to PS. Our findings suggest that PS exposure provides a sufficient signal to inhibit DC maturation and to modulate adaptive immune responses.


INTRODUCTION

Dendritic cells (DCs),3 which are the most potent professional APCs of the immune system, play an important role in the initiation of adaptive immunity (1). DCs acquire, process, and present Ags derived from pathogenic organisms to activate naive T cells, which mount a specific anti-pathogen immune response. DCs also continuously acquire self-Ags from cells that undergo apoptosis as part of normal cell turnover. However, pathological autoimmune conditions occur rarely, suggesting that the ability of DCs to stimulate self-reactive T cells is tightly controlled. The mechanisms permitting DCs to activate vigorous immune responses to most pathogens and to maintain tolerance to tissue-derived "self" Ags are not fully understood (1, 2). There has been a growing body of evidence suggesting that phagocytosis of apoptotic cells under steady state conditions leads to impaired DC maturation and may induce tolerance (3, 4).

snip

.......Recent studies demonstrate that PS-dependent recognition and ingestion of apoptotic cells by macrophages triggers the release of anti-inflammatory cytokines and inhibits the production of proinflammatory cytokines (20, 21, 22). These studies offer a link between the recognition of apoptotic cells and the physiological consequences of their phagocytosis. Whereas the role of PS in the interaction of apoptotic cells with macrophages and the immunological consequence of PS ligation have been broadly delineated, the role of PS in regulating the phagocytosis of apoptotic cells by DCs and the immunological implication of such interactions are not known. Because of the close lineage relationship between macrophages and myeloid DCs, we hypothesized that PS might play a role in the inhibition of myeloid DC maturation. To test this hypothesis, we prepared large unilamellar liposomes containing PS as a simplified model of cell membrane alterations associated with apoptosis. We examined the effect of PS containing liposomes on DC maturation and immunostimulatory capacity. Our results suggest that PS inhibits the ability of DCs to undergo maturation, secrete IL-12, activate T cells, and stimulate IFN-{gamma}-producing CD4+ T cells.....

snip

DISCUSSION

An emerging paradigm suggests that under steady state conditions, apoptotic cells modulate DC function, inducing immune tolerance to self-Ags and preventing autoimmunity (3, 4, 9). Early apoptosis is characterized by loss of membrane asymmetry and exposure of PS on the cell surface (13). PS recently has been shown to play a central role in the recognition of apoptotic cells by macrophages and may be a signal to secrete anti-inflammatory cytokines (17, 20). However, the effects of PS on the maturation and function of human monocyte-derived DCs, whose lineage is closely related to macrophages, have not been well described. We found that PS, which is recognized specifically by DCs, triggers phagocytosis and plays a key role in modulating DC maturation and function....

....Our findings, for the first time, demonstrate that PS is specifically recognized via PSR expressed on the surface of DCs and triggers phagocytosis....

...Previous reports have suggested that iDCs can induce immune unresponsiveness in vitro and in vivo, possibly due to reduced Ag presentation and T cell costimulation (38, 39, 40, 41). Inhibition of DC maturation by exposure to PS is a potential mechanism for inducing immune unresponsiveness or tolerance. We found that DCs exposed to PS had impaired ability to activate allogeneic T cells (Fig. 5, A and B) and to stimulate IFN-{gamma} production (Fig. 6, A and C). Increasing the ratio of DCs to responders restored the proliferation of allogeneic T cells; however, IFN-{gamma} production by allogeneic CD4+ T cells was still impaired. Increased susceptibility to apoptosis by DCs exposed to PS after LPS treatment could not explain the inability to stimulate IFN-{gamma}-producing T cells in vitro, because IL-4-producing T cells were still induced. Furthermore, exogenous IL-12, which does not affect DC viability, restored IFN-{gamma} production by T cells. The findings suggest that PS did not simply inhibit the ability to activate T cells, but selectively modulated the ability to induce IFN-{gamma}-producing T cells.

....Taken together, these findings suggest that DCs exposed to PS would fail to initiate and may extinguish cellular immune responses.....

...Our findings suggest that PS exposure directly inhibits DC maturation and modulates their ability to activate T cell responses. PS is specifically recognized by DCs and triggers phagocytosis via the PSR. Our findings suggest that PS modulates the adaptive immune response at three different levels: 1) PS inhibits survival, Ag presentation, and costimulation by DCs, leading to ineffective T cell proliferation; 2) PS inhibits IL-12p70 secretion by DCs, diminishing the ability to stimulate IFN-{gamma}-producing T cells characteristic of Th1 responses; and 3) DCs exposed to PS have reduced ability to stimulate the proliferation of activated CD8+ T cells, even in the presence of abundant Ags. PS may synergize with additional signals, such as CD200, IL-10, and TGF-{beta}, expressed by apoptotic, inflammatory, or stromal cells (20, 22, 50, 51, 56, 65, 66). Further understanding of the mechanisms by which PS modulates DC function may lead to the development of effective immunotherapies for autoimmune diseases and for cancer.







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REQUIRED READING #3 of 5 (abridged) ------





Apoptotic cells, through transforming growth factor-beta, coordinately induce
anti-inflammatory and suppress pro-inflammatory eicosanoid and NO
synthesis in murine macrophages.



Celio G. Freire-de-Lima∗†‡2, Yi Qun Xiao†‡, Shyra J. Gardai†, Donna L. Bratton†, William P.
Schiemann† and Peter M. Henson†
*Instituto de Biofísica Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro,
RJ 21944-970, Brazil
†Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research
Center, 1400 Jackson Street, Denver, Colorado 80206

Running title: TGF-beta modulates inflammatory eicosanoids




http://www.jbc.org/cgi/reprint/M605146200v1





--------------




In the studies reported here, we showed that the
TGF-beta induction by apoptotic cells was
dependent on exposed PS



...............



These results strongly
suggest that the apoptotic cell inhibition of
pro-inflammatory mediator production is
pleiotropic and significantly dependent on the
stimulation of TGF-beta production.



...............




The
implication is that recognition of PS drives the
production of TGF-beta and the downstream antiinflammatory
responses reported herein.



..............




The induction of TGF-beta itself
could be attributed to exposed
phosphatidylserine on the apoptotic cells,
which therefore, appears to drive the
balanced inflammatory mediator responses.



..............




Apoptotic cells are rapidly engulfed by
adjacent tissue cells or macrophages before
they can release pro-inflammatory/proimmunogenic
intracellular contents. In
addition, recognition of the apoptotic cells is
actively anti-inflammatory and antiimmunogenic
with generation of antiinflammatory
mediators such as
transforming growth factor-beta (TGF-beta) and
anti-inflammatory eicosanoids. Here, we have
investigated the role played by the induction
of TGF-beta in the coordinate expression of antiinflammatory
eicosanoids or PPARγ and in
the suppression of pro-inflammatory lipid
mediators and nitric oxide (NO).



................




As a
cell becomes apoptotic, it is generally removed
in situ by near-neighbor cells or macrophages in
a quiet, almost invisible fashion; that is, the
process does not induce a local tissue reaction.
In fact, recognition and removal of apoptotic
cells is normally both anti-inflammatory and
anti-immunogenic (6-9).



...............




The interaction and recognition are triggered by
surface changes on the apoptotic cells.



.................



there is considerable evidence to implicate PS as
the main stimulus for the anti-inflammatory or
anti-immunogenic effects (6-8,14-16).



...............




A major anti-inflammatory mediator induced in
response to apoptotic cells, mAb217 or PS
liposomes is TGF-beta (6,8,16). Blockade of TGF-
beta has been shown to reverse the suppressive
effects of apoptotic cells or PS in vivo on either
inflammation or adaptive immunity (7,8).



................




A key issue, therefore, is whether apoptotic cellinduced
TGF-beta, acting in an autocrine/paracrine
fashion, mediates the alterations in eicosanoid
generation. By use of a dominant negative TGF-
beta receptor construct we have been able to show
that apoptotic cells stimulate via their induction
of active TGF-beta, a co-ordinate production of
generally anti-inflammatory, and simultaneous
inhibition of generally pro-inflammatory,
eicosanoids.



................




Results
Apoptotic cells or antibody to PSRS on murine
macrophages stimulate production of TGF- beta
and concomitant blockade of LPS-induced
TNF alpha, NO and iNOS.



.................




Discussion
Apoptotic cells are known to induce an antiinflammatory
and anti-immunogenic response,
in part mediated by their induction of active
TGF-beta in responding cells. Here we show that
the effect of the apoptotic cells is to drive a
complex coordinated inhibition of potentially
inflammatory mediators along with induction of
potentially anti-inflammatory molecules in
macrophages that are orchestrated by the TGF-beta
production.



.................




The observations required the demonstration of
TGF-beta production in response to the apoptotic
cells – shown earlier by numerous investigators
and confirmed herein. A number of ligands have
been demonstrated on apoptotic cells that can
interact with a number of “receptors” on
responding cells, in this case macrophages.
Additionally there are a large group of “bridge”
molecules (see ref. 39) that can link the
apoptotic cell ligands to the receptors. We have
suggested that two important ligands are
phosphatidylserine (PS) and calreticulin. The
latter, as well as the collectin family of bridge
molecules (40) has been suggested to interact
with LRP as a receptor and, in isolation, seems
to induce a more pro-inflammatory response
(5,13). On the other hand, PS and its receptors
and possibly some or all of its bridge molecules
appear to induce the anti-inflammatory effects
and, in most cases, to act in a dominant fashion
in the normal response to apoptotic cells.
Necrotic cells are usually thought to be proinflammatory
(see for example 9,15) and may
have reversed this PS-driven dominance. Other
studies that have suggested that apoptotic cells
can in some circumstances act in a proinflammatory
fashion may also reflect variations
in balance between pro-inflammatory (e.g. LRP)
versus anti-inflammatory (e.g. PS driven)
responses.



................




The results indicate a complex effect of
apoptotic cells acting through release of TGF-beta
to upregulate generally anti-inflammatory
mediators and inhibit the production of proinflammatory
molecules.








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REQUIRED READING #4 of 5 (abridged) ------





The influence on the immunomodulatory effects of dying and
dead cells of Annexin V




The Journal of Leukocyte Biology, Jan, 2007



http://www.jleukbio.org/cgi/rapidpdf/jlb.0306166v1




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Abstract: Apoptotic and necrotic cells expose
phosphatidylserine (PS). This membrane modifi-
cation ensures a swift recognition and uptake by
phagocytes of the dying and dead cells. Annexin
V (AxV) preferentially binds to anionic phospholipids
and thereby, modulates the clearance process.
First, we analyzed the influence of AxV on
the immunogenicity of apoptotic cells. The addition
to apoptotic cells of AxV prior to their injection
into mice increased their immunogenicity
significantly. Next, we studied the influence of
endogenous AxV on the allogeneic reaction
against apoptotic and necrotic cells. To preserve
heat-labile, short-lived “danger signals,” we induced
necrosis by mechanical stress. Wild-type
mice showed a strong, allogeneic delayed-type
hypersensitivity (DTH) reaction. In contrast,
AxV-deficient animals showed almost no allogeneic
DTH reaction, indicating that endogenous
AxV increases the immune response against dead
cells. Furthermore, AxV-deficient macrophages
had a higher immunosuppressive potential in
vitro. Next, we analyzed the influence of AxV on
chronic macrophage infection with HIV-1,
known to expose PS on its surface. The infectivity
in human macrophages of HIV-1 was reduced
significantly in the presence of AxV. Finally, we
show that AxV also blocked the in vitro uptake by
macrophages of primary necrotic cells. Similar
to apoptotic cells, necrotic cells generated by
heat treatment displayed an anti-inflammatory
activity. In contrast, mechanical stress-induced
necrotic cells led to a decreased secretion of
IL-10, indicating a more inflammatory potential.
From the experiments presented above, we
conclude that AxV influences the clearance of
several PS-exposing particles such as viruses,
dying, and dead cells. J. Leukoc. Biol. 81:
000–000; 2007.


In healthy situations, cells dying by apoptosis maintain their
membrane integrity until they get cleared. Cell shrinkage leads
to formation of apoptotic bodies containing organelles. Nevertheless,
the dead corpse still has an important message: “No
inflammation, please!”
We were asking the question of whether an interference with
the anti-inflammatory clearance by macrophages of apoptotic
cells, mainly mediated by PS recognition, consecutively restores
the immunogenicity of apoptotic cells in vivo. For this
purpose, mice were immunized with apoptotic cells in the
presence or absence of the PS-binding protein AxV. Using
AxV-deficient mice [21], we further analyzed the physiological
function of AxV in the induction of an immune response
against apoptotic and necrotic cells. PS is also expressed on
monocytes as part of their differentiation program [22]. Many
viruses including HIV cause extensive apoptosis, and infected
monocytes/macrophages therefore express elevated levels of
PS, which consecutively, can also be found in the outer membrane
of the enveloped retrovirus [23]. Using an in vitro culture
system, we examined whether, like the swift uptake of apoptotic
cells, the AxV can also block the silent entry of HIV-1 into
human macrophages. To better understand the mechanism how
PS exposing AxV-binding particles modulates the immune
response, we examined the cytokine secretion of activated
human macrophages and peritoneal macrophages from AxVdeficient
mice after contact with dying and dead cells.



DISCUSSION
Apoptosis is defined as programmed cell death or cellular
suicide, whereas necrosis arises as a result of a violent external
stimulus. A hallmark of apoptotic cells, in contrast to necrotic
ones, is that they maintain their membrane integrity over time.
Thus, the release of intracellular components, which could
damage the surrounding tissue, induce inflammation, or elicit
immune responses, is avoided [26]. To ensure immediate recognition
and uptake by phagocytes, apoptotic cells undergo
early membrane modifications. One such event is the exposure
of PS in the outer leaflet of the plasma membrane associated
with a loss of phospholipid asymmetry. Phagocytes interact
with PS on apoptotic cells mainly through secreted bridging
adaptor proteins, also called opsonins. The latter are important
for a high-capacity clearance of apoptotic cells [27].


The recognition of exposed PS triggers the release of immunosuppressive
cytokines [14, 15, 28], which quench inflammation
and prevent the maturation of antigen-presenting dendritic
cells (DC). Apoptotic cells per se do influence the production
of soluble pattern recognition receptors such as pertussis toxin
3 by maturing DC [29]. Furthermore, the opsonization of apoptotic
cells by soluble factors influences their antigen presentation
by DC and thereby, modulates their immunogenicity
[30]. Recently, it was discussed that alterations of the plasma
membrane phospholipid distribution have important influences,
not only for cell clearance but also for the execution of
apoptosis [31].


AxV is a natural-occurring, specific ligand for PS and may
consequently interfere in vivo with the immunosuppressive
effects of apoptotic cells. We showed that the immunogenicity
of apoptotic cells could be restored by the addition of AxV.
During apoptotic as well as necrotic cell death, autoantigens
are cleaved or otherwise modified, and these modifications may
render cryptic epitopes immune-dominant (reviewed in ref.
[32]). When interfering with the clearance of dying cells, DC
may acquire modified autoantigens such as apoptotic nuclei
and chromatin, and consequently, autoreactive T cells can be
activated. This may also lead to chronic autoimmunity, as is the
case in SLE [24]. It was also shown that an impaired clearance
of dying tumor cells can lead to tumor rejection. AxV decreased
apoptotic cell uptake by peritoneal macrophages and
concomitantly increased their uptake by CD8
/11c
DC [33].


When AxV binds to apoptotic cells, it “crystallizes” as an
extended two-dimensional network. It has an autocrine function
and activates away from cell entry. This results in the
internalization of the PS-expressing membrane patches from
the surfaces of apoptotic macrophages [35]. We have shown
previously that AxV shows positive cooperativity for PS binding
on membranes of apoptotic and necrotic but not of viable
cells. We suggested that phagocytes can differentiate between
dying and viable cells by means of PS clustering and consecutively,
by the lateral mobility of the cellular membranes [36].
PS-mediated phagocytosis of apoptotic cells suppresses inflammatory
signals such as TNF-, IFN- , and NO and also triggers
the production of TGF-, an anti-inflammatory cytokine
[15]. We have previously shown that necrotic cells, like apoptotic
ones, can also engage CD36 and a surface receptor
recognized by mAb 217G8E9. They thereby mediate antiinflammatory
signals [12]. Here, we show that necrotic cells
induced by heat treatment promote the release of anti-inflammatory
cytokines by LPS-activated macrophages, as is the case
for apoptotic cells. Heat-induced necrosis destroys heat-labile
and short-lived danger signals. The uptake of the necrotic cells
then becomes anti-inflammatory. In contrast, mechanical
stress-induced necrotic cells led to a decreased secretion of the
anti-inflammatory cytokine IL-10 and consecutively, displayed
a more immunostimulatory phenotype. We conclude that the
proinflammatory properties of necrotic cells depend on the
inductor of necrosis. Furthermore, we added AxV to this experimental
setting and found a significant, further up-regulation
of IL-10 secretion in the case of heat-necrotized cells but
not in the case of stress-induced necrotic cells (not shown),
further confirming the higher proinflammatory potency of mechanical
stress-induced necrotic cells when compared with
heat-induced necrosis.



The primary force of the immune system is the need to detect
and protect against danger [37]. One mode of action of danger
signals is to stimulate the maturation and activation of DC
necessary for the initiation of primary and secondary immune
responses. Endogenous danger signals, released by tissues
undergoing stress, damage, or abnormal death, and also exogenous
danger signals, elaborated by pathogens, can contribute
to this stimulation. Some endogenous danger signals, which
have been discovered recently are heat-shock proteins, nucleotides,
reactive oxygen intermediates, extracellular matrix
breakdown products, neuromediators, cytokines such as the
IFNs [38], as well as uric acid [39], ATP [40, 41], and HMGB1
[16, 42], which as well as its best-characterized receptor for
advanced glycation end products, is important for the maturation
of human plasmacytoid DC [43] and also controls T cell
activation [44]. Furthermore, the release of intracellular factors
from necrotic tumor cells can promote reactive angiogenesis,
stromal proliferation, and local immune suppression [45]. Future
work has to be focused strongly on all such “alarmins”
[46], which signal the body: “Attention, tissue damage has
occurred!”


Many viral infections (such as HIV) lead to the release of
several proinflammatory cytokines and to extensive apoptosis.
The latter may contribute to the impaired immune response
accompanying such infections [50, 51]. Recently, it has been
shown that PS can be detected at the surface of HIV-1 and that
AxV can be used to enrich these virus particles. Furthermore,
the infection by HIV-1 strains of monocytes can be compromised
upon the addition of AxV during the infection process
[23]. Here, we demonstrated that clinically relevant, chronic
infections of HMDM with HIV-1 isolates can be inhibited by a
single application of AxV. In addition, Ma et al. [52] showed
that Annexin II is necessary for HIV-1 uptake into human
macrophages. This HIV-1 PS interaction with Annexin II could
be disrupted by a secretory leukocyte protease inhibitor [52].
Taken together, AxV efficiently blocks the silent entry of
HIV into macrophages as well as the swift clearance of apoptotic
and necrotic cells. The disturbed, PS-dependent clearance
by macrophages of apoptotic cells leads to the accumulation
of the latter and to the occurrence of late apoptotic cells,
which have lost their membrane integrities. The proinflammatory
cytokine profile of the late clearance and endogenous
danger signals released from cells, which have lost their membrane
integrity, build a proinflammatory microenvironment. DC
may then pick up antigens derived from the dying cells in a
proinflammatory milieu and present the cell-derived antigens
together with costimulation (Fig. 5). We showed that AxV
increased the immunogenicity of apoptotic cells significantly.
In addition, immunization with mechanical stress-induced necrotic
cells was used to mimic the above-mentioned scenario.
Only in the presence of endogenous AxV (WT animals) was a
specific immune response against the dead cells to be observed.
Furthermore, endogenous AxV led to a decreased
secretion of IL-10 in peritoneal macrophages in response to
mechanical stress-induced necrotic cells. Examinations of the
in vitro mechanisms underlying the observed effects revealed
that mechanical stress-induced necrotic cells led to an inflammatory
modulation of macrophages in contrast to apoptotic
cells and heat-induced necrotic ones. In conclusion, apoptotic
and necrotic cells strongly influence the immune response.
AxV is an important modulator of this interaction. It inhibits
certain viral infections and increases the immune response
against tumor cells and more general, that against dying and
dead cells.








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REQUIRED READING #5 of 5 (abridged) ------





Cancer Cell Immune Escape and Tumor Progression by Exploitation
of Anti-Inflammatory and Pro-Inflammatory Responses





Cancer Biology & Therapy 4:9, 924-933, September 2005




http://www.landesbioscience.com/journals/cbt/article/kim4-9.pdf




-----------





Apoptotic cells can be eliminated by phagocytosis, which is mediated by antigen-
presenting cells (APCs), such as macrophages and dendritic cells (DCs), through
phosphatidylserine (PS) on apoptotic cells and phosphatidylserine receptor (PSR) on
APCs. The phagocytosis of apoptotic cells by macrophages is strictly regulated by not
only the inflammatory reaction, but also by an increase in anti-inflammatory factors such
as IL-10, TGF-b, and prostaglandin E2 (PGE2), leading to an anti-inflammatory situation,
whereby apoptosis contributes to a noninflammatory response. However, because PS and
PSR are expressed in cancer cells, shed soluble phosphatidylserine (sPS) can interact with
the PS receptor on macrophages, which promotes an anti-inflammatory response to
macrophages that may lead to immune escape. The sPS derived from cancer cells also
reacts with the PSR on the cancer cells to produce IL-10, TGF-b, and PGE2, which can
cause suppression of anti-tumor immunity through the anti-inflammatory response to
macrophages, which produces tumor-associated macrophages. Furthermore, sPS and
TGF-b inhibit the maturation of immature DCs, resulting in a functional inhibition of DCs.
The potential roles of PS and PSR in cancer cells and macrophages in immune escape
mediated by sPS and anti-inflammatory factors are discussed, which may explain their
dual regulation of anti- and pro-inflammatory responses during tumor progression.



-----------------




the PS/PSR-mediated
anti-inflammatory response can be induced by soluble phosphatidylserine (sPS) derived
from cancer cells. The sPS can interact with either APCs or PSR on cancer cells, resulting
in the production of IL-10, TGF-b and PGE2, whereby the function of APCs is inhibited.16,17
Thus, the production of anti-inflammatory cytokines mediated by sPS/PSR on APCs and
cancer cells may promote immunosuppression, which impairs macrophage cytotoxicity
and DC function. The impairment
prevents an immune response in the
tumor microenvironment and facilitates
tumor progression and metastasis.18,19



-------------



The shift
to an anti-inflammatory response to immune cells mediated by
TAM in response to sPS from cancer cells may result in the inhibition
of maturation of DCs and their migration to a primary lymphoid organ
for activation of T-cells.



----------------



The
production of soluble factors such as IL-10 and TGF-b helps cancer
cells to avoid immune recognition through inhibition of development
and activity of immune cells.



-----------------



Given that the immunosuppressive mediators such as IL-10,
TGF-b, and PGE2 play an important role in promoting immune
escape in the microenvironment of cancer cells, the release of these
cytokines take place from TAMs as well as from cancer cells.42



-----------------



vascular endothelial cells in tumors
externalize PS to their luminal surface, whereas PS is absent from the
external surface of vascular endothelial cells in normal tissues.19 (Thorpe/Ran, j.)



-------------



the sequential immune response by TAM
and DCs can be abrogated by sPS derived from cancer cells. The
enforced anti-inflammatory response by sPS-not only by interaction
with the PSR on TAM but also with the PSR on immature DCs to
inhibit their maturation-may cause immune escape and tumor
proliferation. Furthermore, the sPS derived from cancer cells binds
to these cells’ own PSR, resulting in the production of IL-10,
TGF-b, and PGE2 in the tumor microenvironment and facilitation
of tumor proliferation.



---------------



During the anti-inflammatory response, the TGF-b derived from
TAM prevents the maturation of antigen-presenting DCs, thereby
inhibiting the activation of natural killer cells and CTLs.86 In addition,
the TGF-b promotes the proliferation of stromal cells such as fibroblasts
and macrophages and induces them to secrete angiogenic and
cell survival factors that stimulate tumor proliferation through
NF-kB, which is activated by Akt.52 These stromal cells also produce
Th2 cytokines, such as IL-4 and IL-10, as well as PGE2 as a
result of TGF-b secretion.



-----------------



Thus, the production of
IL-10, TGF-b, and PGE2 from TAM mediated by sPS or hydroxide
plays a critical role in immune escape.




-----------




j