Fig. (3) CD45 cross-linking inhibits IL-2-induced proliferation of antigen specific T cells and non-malignant skin T cells but not malignant skin T cells. Round bottom tissue culture plates were coated with (A) anti-CD28 mAbs, (A, B) anti-CD45 mAbs or medium. Then (A) two different clones of antigen specific T cells (Ag T cell 1/2) from peripheral blood, (B, left) non-malignant skin T cells (MyLa1928) or (B, right) malignant T cells (MyLa2000) were added to the wells and incubated for 120 hours in culture medium with or without IL-2. [³H]thymidine was added 24 hours before harvest and the incorporation measured in a scintillation counter. The results are expressed as mean counts per minute (cpm) from triplicate cultures.