Assessment of lymphocyte homing or IFN-γ production by memory CD4 T cells from tumor-bearing mice. (A) Spleen cells (top row) and single cell suspensions of in vivo growing tumors (bottom row) were stained with anti—CD4-FITC and intracellularly with anti—IFN-γ-PE. Cells were restimulated with PdBu and ionomycin (left panels) or DCs and C5 peptide (right panels) overnight. Brefeldin A was added for the last 4 hours of culture. The dot plots show staining on gated CD4 T cells. Numbers refer to percentages of IFN-γ—positive cells. (B) MHC class II and costimulatory molecule expression on tumor cells. C5-transfected LK35 tumor cells or ex vivo tumor cells were stained with anti—MHC class II—FITC (clone 14.4.4; top row). Background staining is shown with a dotted line; mean fluorescence values are shown in upper righthand corners. C5-transfected LK35 tumor cells (...) and ex vivo tumor cells (—) also were stained with anti—B7.1-PE or anti—B7.2-PE (bottom row). Memory T cells were derived from mice that had been injected with naive A18 TCR transgenic T cells and syngeneic DCs.