Cross-linking of MHC class II molecules on human dendritic cells induces phosphorylation of the PLCγ2 and p72syk but not PLCγ1. (A) PLCγ1. (B) PLCγ2. (C) p72syk. After stimulation as described in the legend to Figure 2, DC lysates were precleared for 2 hours and immunoprecipitated by incubation with specific antibody at 10 μg/mL. Tyrosine phosphorylation was analyzed by Western blotting of heat-denatured immunoprecipitates with an antibody specific for phosphotyrosine (4G10). Each membrane was rehybridized with antigen-specific antibody to ensure equal loading. IgG1 (lane 1), human LAG-3Ig (lane 2), I3 (pan class II–specific mAb, lane 3). Results are representative of 3 experiments performed on different DC samples.