FIG. 5.

CD3 cross-linking induces PLCγ1 tyrosine phosphorylation in P116 T cells. (A) Jurkat and P116 T cells were stimulated by CD3 cross-linking for 2 min at 37°C with the indicated concentration of purified UCHT1 MAb. PLCγ1 was immunoprecipitated from WCLs and immunoblotted for phosphotyrosine with the 4G10 MAb (top). The membrane was then stripped and blotted for PLCγ1 (bottom). The presence of active Erk in the WCLs (middle) was measured as described in the legend to Fig. 1. (B) Jurkat and P116 T cells were stimulated by CD3 cross-linking at 37°C with OKT3 ascites (1:50) for the indicated times. WCLs were analyzed as in panel A.