ROLE OF MONOCYTES IN THE UP-REGULATION OF THE EARLY ACTIVATION MARKERCD69 ON B-MURINE-LYMPHOCYTE AND T-MURINE-LYMPHOCYTE INDUCED BY MICROBIAL MITOGENS

CD69 is an early marker of lymphoid cell activation. The authors repor t on an up-regulation of CD69 in splenic B and T cells of C57B1/6 mice after administration of lipopolysaccharide (LPS) or microbial immunos uppressive/mitogenic (ISM) proteins produced by C. albicans (p43) and African Swine Fever Virus (p36). This up-regulation of CD69 was observ ed 6 and 24 h after mitogenic treatments. The same pattern of increase d CD69 expression was observed in the lymph nodes of mice treated with p43 or LPS, whereas p36 treatment failed to induce increased CD69 exp ression in this organ. Intracellular calcium mobilization was induced in splenic B and T lymphocytes after incubation of total spleen cells with LPS, p43 or p36. This increase was higher in B than in T cells. I ncreased calcium mobilization was also seen in lymph node B cells afte r incubation with p43 or p36 and in lymph node T cells after p43 stimu lation. Upregulation of CD69 expression on B and T cells was also obse rved after in vitro stimulation of spleen cells with the three mitogen s used. Similar results were obtained with culture supernatants of mac rophage/ monocyte (M phi) cells activated with LPS (LPS/M phi CS). Sti mulation of M phi cells with LPS or with the ISM proteins is demonstra ted by the increased production of nitrites by these cells. The increa sed in vitro expression of CD69 was, however, not abolished by monoclo nal antibodies to Mb cytokines such as IL-6, IL-10 or TNF alpha. No in creased expression of CD69 was found in vitro on purified B or T cells , even when mixed upon stimulation with p43, p36, LPS or with LPS/M ph i CS. However, an increase in the expression of CD69 was observed on B cells co-cultured with M phi cells after treatment with LPS or p36. A ll three mitogens failed to induce increased CD69 expression on cultur ed T cells mixed with M phi cells.