FIG. 2.

Cross-linking of inhibitory molecules down-regulates antigen-specific and total IgG production. (A) Total IgG antibodies specific for the indicated antigens (Ag) were produced in a T-cell-B-cell cooperation test. The supernatant was collected after 6 days, and IgG specific for TT and PPD was determined by ELISA. The averages ± standard deviations (error bars) of three different experiments are shown. Similar results were obtained with two other donors. (B) B cells were stimulated with CD40L-transfected cells plus IL-4 or with LPS plus IL-4, a system mimicking the interaction between T and B lymphocytes, in the presence (+) of cross-linked MAbs to CD152, CD85j, and LAIR-1. Anti-CD44 MAb was included as an irrelevant isotype-matched control. The columns indicate the IgG concentrations in the culture supernatants after 6 days of stimulation.