Factor requirements for activation and proliferation steps of human CD2+CD3-CD4-CD8- early thymocytes

Dalloul AH, Mossalayi MD, Delagi K, Bertho JM, Debre P.
European Journal of Immunology - Volume 19, Issue 11, 1989, Pages 1985-1990

Human CD2+CD3-CD4-CD8- thymocytes were shown to display high in vitro growth ability although their factor requirements for activation and proliferation are not fully known. We have thus isolated these precursors and assayed their activation and proliferation potentials in response to various factors. Our results indicate that these cells proliferate in reponse to phytohemagglutinin (PHA), recombinant interleukin 2 (rIL2) and rIL 4. Simultaneous addition of anti-CD2(I + III) monoclonal antibodies (mAb) and rIL2 highly increased cell growth while IL4-induced proliferation was not enhanced upon addition of anti-CD2. Anti-CD2 and PHA, but not IL2, induced intracytoplasmic Ca2+ influx phosphatidyl inositol turnover as well as IL2 receptor expression. Sequential studies indicated that CD2 triggering enable many more CD2+ precursors to respond to rIL2. Endogenous IL2 synthesis was necessary for PHA-induced cell growth. Neither of these in vitro treatment were able to induce membrane expression of CD3, CD4 or CD8 on CD2+ cells.