Figure 3.

Differences in the proliferative response to secondary stimulation between alloantigen-primed PKH-26^dim CBTL and PKH-26^dim PBTL. Alloantigen-primed PKH-26^dim CBTL do not proliferate upon secondary stimulation with CD3 plus CD28 (CD3/CD28), even in the presence of low-dose (5 units/ml) IL-2 (CD3/CD28/LD IL2). Secondary stimulation with PMA plus ionomycin (PMA/Iono) or PMA plus alloantigen (PMA/Allo) induces proliferation but not stimulation with ionomycin plus alloantigen (Iono/Allo). High-dose (50–100 units/ml) IL-2, either alone (HD IL2) or combined with alloantigen (HD IL2/Allo), overcomes the secondary proliferative block of PKH-26^dim CBTL. Experiments with low-dose IL-2 alone (LD-IL2) and PMA alone (PMA) are also presented, showing that neither can induce cell proliferation in PKH-26^dim CBTL. Results represent the mean of three different experiments. Each experiment was performed in triplicate.