FIG. 3.

Activation of MEK and ERK/MAP kinases in response to T-cell-tropic gp120 or anti-CD4 antibodies. Jurkat cells were preincubated on ice for 60 min with recombinant gp120 IIIB (1 μg/ml) or anti-CD4 (α-CD4) antibody (5 μg/ml) or left untreated (control) and then incubated at 37°C for the indicated times before lysis. Proteins (50 μg per lane) were resolved by SDS-PAGE, transferred to a nitrocellulose membrane, and probed with antibodies specific for phosphorylated forms of MEK1/2 (MEK-P) and ERK1/2 (ERK1/2-P) as well as with antibodies specific for total MEK and ERK. The positions of molecular weight markers (in kilodaltons) and kinases are indicated.