Concentration of IgG1 and IgG2a allotypes in serum of nude and normal allotype-congenic mice.

BALB/c (C) and C57BL/6 (B6) allotype--congenic strains of mice (C, C.B, B6, B6.C) were made congenitally anthymic by the introduction of the mutant nude gene (nu). The resulting nude mice (C.nu, C.B.nu, B6.nu and B6.C.nu) were found to produce highly variable quantities of IgG1 and IgG2a. Whether these mice showed high, normal, or low quantities of IgG1 or IgG2a relative to their normal counterparts depended on their age and genetic background. In all nude mice, IgG1 production appeared more sensitive to the loss of T cells than did IgG2a production. An extreme example of this was the deficiency of IgG1 but not IgG2a in adult B6.nu and B6.C.nu mice. Substantial quantities of both IgG1 and IgG2a were found in adult C.nu and C.B.nu mice.