Humoral response of hs3b/hs4-deficient mice immunized with ovalbumin. ELISA analysis of ovalbumin-specific immunoglobulin isotype secretion in sera of 8-week-old immunized mice. Antibody levels are expressed in arbitrary units by comparison with a control serum; time after immunization is indicated in days. Each point is the mean of serum determinations from 4 Δhs3b4 homozygous (gray curve) or wt control animals (black curve). The amount of ovalbumin-specific immunoglobulin was quantified by curve comparison with a pool of sera from ovalbumin-immunized wt mice. This experiment is representative of 2 independent experiments.