Absence of CD47 impairs mouse IgG but not IgM response following immunization. Six male WT or CD47−/− mice were immunized i.p. with peptide, followed by boosters on days 21, 35 and 49, with serum collection on day 7 after each immunization. A) Serum IgG measured by ELISA. B) Serum IgM and IgG levels asssessed by Western blotting C) Serum IgG1, IgG2b, IgG2c and IgG3 levels measured by ELISA. *, P<0.05; **, P<0.01.