Table 1.

B cell phenotype of candidate gene knockouts

Gene	Viability	Knockout phenotype	Ref.
Lyn	Viable	↓ B cell numbers, ↓ surface IgM levels, ↑ BCR responses, ↑ serum IgM levels, slightly ↓ T-dependent and T-independent responses, ↑ B-1 cells, autoantibodies with age	24, 28–32
Fyn	Viable	Normal B cell numbers, normal BCR responses, ↓ IL-5 response	33, 34
p85α	Perinatal lethality	Like xid with more severe block at proB to preB stage	35, 36
CD19	Viable	↓ B cell numbers, ↓ BCR responses, ↓ serum Ig levels, ↓ T-dependent responses, normal or ↑ T-independent responses, ↓ B-1 cells	37–39
Gαq	Viable	No B cell phenotype described	40
Gα11	Viable	No B cell phenotype described	41
SHIP	Viable	↓ B cell numbers, ↓ surface IgM levels, ↑ BCR responses, ↓ FcγRIIb-mediated inhibition of BCR, ↑ serum Ig levels, normal T-dependent responses, ↑ T-independent responses	42–44
PTEN	Embryonic lethal	In +/− mice: ↑ number of activated B cells (polyclonal expansion), ↑ autoantibodies	45–49
CD22	Viable	↓ B cell numbers, ↓ surface IgM levels, ↑ BCR responses, ↑ serum IgM levels, ↓ T-independent responses, normal T-dependent responses, ↑ B-1 cells, autoantibodies with age	38, 50–52
PKCβ	Viable	Like xid	21

The B cell phenotypes of mice deficient in each candidate gene tested are indicated.