Figure 2. FK506 derived from FK506 treated DC blocks T cell activation.
(A) Transcription, translation and translocation through the secretory pathway are not required for FKDC to produce a T cell inhibitor. DC were pretreated with actinomycin, emetine, brefeldin A or media prior to treatment with FK506 or media control and washed extensively. T cells were stimulated for 4 hr with anti-CD3/28 or media and mixed with treated DC. Data are mean IFNγ mRNA induction of stimulated vs unstimulated control T cell groups + standard deviation (SD) of triplicate wells. (B) FKDC were washed and supernatants measured daily via ELISA. Levels after last wash were undetectable. Dashed line indicates FK506 concentration that inhibits 50% induction of IL2. Data are nM ± SD of triplicate wells. (C) FKDC or untreated DC supernatants treated with FK-1 (anti-FK506) or anti-KLH (isotype control) antibody depletion. Depleted supernatants were added to anti-CD3/28 stimulated T cells. Data are mean IFNγ mRNA induction + SD of triplicate wells. (D) DCs treated with 0.5 μM rapamycin or media control for 18 hr prior to treatment with 0.5 μM FK506 or media control for 1 hr and washed extensively. Syngeneic CD4+ T cells were cultured with various treated DCs and CD3/28 beads for 4 hr. Data are mean fold induction of IL2 mRNA of stimulated vs unstimulated cells ± SD. p values were obtained using two-tailed unpaired t-test. Data are representative of three independent experiments.