Effect of TCR stimulation on TR Ca²⁺ responses and cell-surface expression. Jurkat cells (A) or J45.01 cells (B) were incubated for 16 hours with either control medium (□) or the IgM anti-CD3 MoAb 235 (▨), and Ca²⁺ responses were measured in response to 50 nmol/L thrombin or 40 μmol/L SFLLRN. Values represent the mean ±SD of triplicate determinations. To measure effects of TCR stimulation on cell-surface expression, flow cytometry was performed using the negative control MoAb (dotted lines), the antihuman TR MoAb ATAP2 (solid lines), or the IgG anti-CD3 MoAb OKT3 (dashed lines). (C) Unstimulated Jurkat cells; (D) unstimulated J45.01 cells; (E) Jurkat cells stimulated with anti-CD3; and (F ) J45.01 cells stimulated with anti-CD3.