Following the development of a CD4 T cell response in vivo: From activation to memory formation

The in vivo differentiation of CD4 T cells from naive to memory cells was f ollowed after their adoptive transfer together with syngeneic dendritic cel ls into MHC mismatched adoptive hosts lacking lymphocytes and NK cells. Fun ctional and molecular changes were measured as the antigenic stimulus, prov ided by the cotransferred dendritic cells, disappeared. Memory cells as opp osed to effector cells show an inversion in the relative expression of Bcl- 2 family members in favor of antiapoptotic molecules, and compared with nai ve cells they have an increased ratio of bcl-x(L) to bcl-2. They differ qua litatively from naive T cells, suggesting that accelerated CD4 memory respo nses can occur without the need for increased frequencies of specific T cel ls.