I asked Grok to summarise in 2-300 words. See how it reads.
Summary of the Harvard–Boston Children’s Hospital Preprint (November 2025)A study from Harvard Medical School and Boston Children’s Hospital (posted as a preprint in November 2025) reveals that approximately 20% of bone marrow megakaryocytes – the cells traditionally known for producing platelets – constitutively express MHC class II molecules and function as professional antigen-presenting cells (APCs).Using single-cell RNA sequencing, fate-mapping mouse models, and human bone marrow samples, the researchers showed that these megakaryocytes:Take up and process antigens in the bone marrow microenvironment
Present peptides via MHC II to CD4+ T cells
Express co-stimulatory molecules (CD80/CD86) and produce IL-12
Maintain long-term antigen-specific CD4+ T-cell memory, particularly for systemic antigens
Crucially, megakaryocytes appear to serve as a stable, non-migratory reservoir of APCs that can sustain T-cell responses long after peripheral dendritic cells have disappeared.The X post by Dr. Andrew Caravello connects this discovery directly to the durable efficacy of Northwest Biotherapeutics’ DCVax-L (autologous dendritic cells pulsed with whole-tumor lysate) in glioblastoma. In the Phase 3 trial, a subset of patients achieved survival beyond 5–10 years despite receiving only 6–10 vaccine doses over the first year. Caravello argues that tumor antigens delivered by the initial DC vaccinations are carried to the bone marrow, where megakaryocytes pick them up and continuously re-stimulate tumor-specific CD4+ T cells for years – providing a biological explanation for why finite dendritic cell vaccination can yield lifelong tumor control in some patients.In short, the preprint suggests the bone marrow hosts a previously unrecognized “memory APC” platform that may explain long-term responses to several cancer vaccines, particularly whole-tumor-lysate approaches like DCVax-L.(248 words)