Immune responses in congenitally thymus-less mice. II. Quantitative studies of serum immunoglobulins, the antibody response to sheep erythrocytes, and the effect of thymus allografting.
The concentrations of immunoglobulins in the sera of congenitally thymus-less `nude' (nu/nu) mice of various ages were studied by single radial diffusion and compared with those in phenotypically normal nu/+ controls. γM was present in normal concentrations. γA and γG2a concentrations were greatly reduced. γG1 was normal at the time of weaning (28 days of age), but fell progressively thereafter until it was indetectable in most animals more than 60 days old. The primary response to 4 × 107 sheep erythrocytes was studied by haemolytic plaque and serum haemagglutination techniques. Nu/nu mice made subnormal quantities of 19S and little or no 7S antibody. Subcutaneous grafting of neonatal CBA/H thymus at 10–25 days of age was followed by increased survival of nu/nu mice and by the appearance of normal concentrations of γG2a and γG1 globulins and near-normal concentrations of γA. Intraperitoneal injection of 108 CBA/H thymus cells resulted in still higher concentrations of these three proteins. It is concluded that the establishment of normal serum concentrations of γA, γG2a and, especially, γG1 depends upon the presence of funtional T-lymphocytes. γM shows no such T-dependence.