Serum immunoglobulins in nude mice and their heterozygous littermates during ageing.

Serum immunoglobulin (Ig) levels were investigated in 6, 40 and 110 week old congenitally athymic (nude) mice and their heterozygous littermates. Concentrations of IgM, IgG1, IgG2a, IgG2b, IgG3 and IgA were determined by rocket electrophoresis. At 6 weeks of age, IgM was the most prominent serum Ig in both nude and heterozygous mice. Except for IgM and IgG3, some nude mice displayed unquantifiable levels of some of the other Ig classes or subclasses. At this age, the average levels of the various Ig classes and/or subclasses did not differ significantly between the two groups of mice. At the ages of 40 and 110 weeks, most nude mice showed serum Ig spectra in which all classes and subclasses were present. Young (6 week) and middle-aged (40 week) nude mice generally showed a wider variation in Ig levels than did their heterozygous littermates. The most striking differences between aged nude mice and aged heterozygous mice were: (a) the generally decreased levels of IgG2a, IgG2b and IgA; (b) the frequent occurrence of increased serum levels of IgG1; and (c) the increased incidence of homogeneous Ig components ('paraproteins') in the sera of nude mice.