Figure 1.
U937 cells co-stimulate T cells in a CD3-dependent proliferation assay. (a) Increasing numbers of irradiated U937 cells were co-cultured with 2×105 purified tonsillar T cells, in the presence of 0·1 μg/ml CD3 mAb (UCHT1). (b) Increasing numbers of T cells were co-cultured with 104 irradiated U937 cells, in the presence of 0·1 μg/ml CD3 mAb (UCHT1). T-cell proliferation in both (a) and (b) was assessed by [3H]thymidine incorporation between 48 and 64 hr of culture. T cells and U937 together without CD3 mAb, and T cells with CD3 mAb but no U937 cells did not elicit a T-cell response. 5×104 irradiated U937 cells alone gave thymidine incorporation values of 2000 c.p.m. The values shown are the mean [3H]thymidine incorporation of triplicate wells±SD from one experiment. Similar results have been found in at least two other experiments. (c) and (d) Typical U937 – T-cell clusters were seen at ×40 magnification, approximately 48 hr after the start of the assay. (c) 2×105 purified tonsillar T cells, and 104 irradiated U937 cells. (d) As for (c) but with CD3 mAb (0·1 μg/ml).