Flow cytometric analysis of CD45 isoform expression. (A) Purified naive CD4+ T cells (no additional MHC II depletion). These were subsequently stimulated for 6 days with EpCAM-transfected CHO cells armed either with (B) 250 ng/ml bscAb EpCAM x CD3 alone, (C) 250 ng/ml bscAb EpCAM x CD3 and 500 ng/ml heterodimeric B7-1 construct, (D) 250 ng/ml bscAb EpCAM x CD3 and 500 ng/ml B7-1 single-chain construct, (E) 250 ng/ml bscAb EpCAM x CD3 and 500 ng/ml B7-2 single-chain construct, (F) 250 ng/ml bscAb EpCAM x CD3 and 500 ng/ml LFA-3 single-chain construct or with (G) 250 ng/ml bscAb EpCAM x CD3, 125 ng/ml B7-1 single-chain (sc) construct and 500 ng/ml ICAM-1 single-chain (sc) construct. The stimulation pattern of the TCR-like signal (signal 1) and costimulation signal (signal 2) is given in the upper panel. The T cells' corresponding IFN-gamma and IL-4/IL-5 expression profiles are shown in the lower panel.