The role of the C4 isoforms (C4A and C4B) in Nm infection is conflicting with reports that C4 deficiency alone is not significant enough to predispose individuals to bacterial infection (Bishof et al. 1990; Cates et al. 1992; Fasano et al. 1990). The gene discussed is C4A; the disease is hyperinsulinemic hypoglycemia, familial, 4.