Figure 2.

(B) Alloantigen-primed PKH-26^dim CBTL (CB) do not proliferate after secondary stimulation with alloantigen or CD3 plus CD28 activation, whereas PKH-26^dim PBTL (PB) do. PKH-26^bright CBTL and PKH-26^bright PBTL, which were not successfully activated during primary alloresponse, exhibit a vigorous proliferative response when rechallenged with alloantigen or CD3 plus CD28 activation (A). Treatment of PKH-26^dim CBTL with PMA and ionomycin overcomes the proliferative block (B). Results represent the mean of three different experiments. Each experiment was performed in triplicate.