PS is a body own substance that when exposed on the outside of a cell keeps the immune system from cleaning up that damaged/infected cell.
No, PS on the outside of a cell causes its removal by phatocytes. See for example this article
July 1998, Volume 5, Number 7, Pages 551-562 Table of contents Previous Abstract Next Article PDF Review The role of phosphatidylserine in recognition of apoptotic cells by phagocytes Valerie A Fadoka, Donna L Bratton, S Courtney Frasch, Mary L Warner and Peter M Henson
Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado 80206 USA
aAuthor for correspondence: tel: 1-303-398-1281 fax: 1-303-398-1381 email: fadokv@njc.org
Edited by M. Piacentini Abstract
Exposure of phosphatidylserine on the outer leaflet of the plasma membrane is a surface change common to many apoptotic cells. Normally restricted to the inner leaflet, phosphatidylserine appears as a result of decreased aminophospholipid translocase activity and activation of a calcium-dependent scramblase. Phosphatidylserine exposure has several potential biological consequences, one of which is recognition and removal of the apoptotic cell by phagocytes.