B7-1 and B7-2 blockade prevents the increase in serum IgG1 and IgE during Hg-induced autoimmunity.Groups of five mice were treated as described in protocol 1 (Fig. 1). Serum immunoglobulin levels were measured by ELISA as described in the Materials and methods section and are expressed in mg/ml ± s.d. (IgG1) or µg/ml ± s.d. (IgE). From week 2 and thereafter, serum IgG1 and IgE levels were significantly (P < 0·05) lower in mice receiving both anti-B7-1 and anti-B7-2 MoAbs than in mice treated with control MoAbs. Levels of serum IgG1 and IgE were not significantly different in mice receiving single anti-B7-1 or anti-B7-2 MoAb treatment than those in mice treated with control isotypes (except for lower levels of serum IgE at weeks 2 and 3 in mice treated with anti-B7-1, p <0·05). □, Anti-B7-1; ▵, anti-B7-2; ○, anti-B7-1 + anti-B7-2; ♦, isotype control; ▪, mercury alone.