Fig 3. IgG-mediated suppression of primary IgM- and IgG-responses in FcγRIIB KO and FcRγ KO mice.
FcγRIIB KO, FcRγ KO, and BALB/c mice were immunized with 10 μg IgGb anti-SRBC and 5x106 SRBC, SRBC alone, or IgG alone. (A,C) Five days after immunization, the number of spleen cells producing IgM anti-SRBC was assayed. Responses are shown as percentage of the direct PFC response/spleen in mice given SRBC alone (100%, open bars); black bars show responses in mice given IgG and SRBC. Direct PFC/spleen in the respective control groups (receiving antigen alone) were in A: BALB/c, 12,218; FcγRIIB KO, 36,391 (p<0.05) and in C: BALB/c, 57,279; FcRγ KO 40,831. (B,D) Seven to 49 days later, serum levels of IgG anti-SRBC were assayed in ELISA on sera diluted 1:625. Data are representative of one (A, C) or pooled from three (B, D) experiments with each KO strain. p-values denote comparisons between mice immunized with IgG anti-SRBC together with SRBC and mice immunized with SRBC alone. **, p < 0.01; ***, p < 0.001.