COSTIMULATOR DEPENDENCE OF LYMPHOKINE SECRETION BY NAIVE AND ACTIVATED CD4(-LYMPHOCYTES FROM TCR TRANSGENIC MICE() T)

The role of costimulation in Ag-induced responses of naive and differe ntiated IL-2 and IL-4-producing CD4(+) T cells has been examined using cells from mice expressing a transgenic TCR specific for cytochrome c (81-104) + I-E(k). IL-2 secretion by naive and pre-activated T cells is dependent on costimulation, because it is not induced with chemical ly fixed APCs and is significantly inhibited by the B7 antagonist, CTL A4-lg. In contrast, IL-4 secretion by in vitro differentiated Th2-like cells is relatively independent of costimulators. Thus, the requireme nt for costimulation is related more to lymphokine secretion profiles than to the previous activation status of CD4(+) T lymphocytes.