The distribution of cytoplasmic immunoglobulin containing cells over various lymphoid organs of congenitally athymic (nude) mice as a function of age.

The distribution of cells containing cytoplasmic immunoglobulin (C-Ig cells) over various lymphoid organs was studied in congenitally athymic (nude) mice as a function of age. The C-IgM, C-IgG and C-IgA cells were enumerated in spleen, bone marrow, mesenteric lymph node and Peyer's patches of nude mice and their heterozygous littermates of 6, 40 and 100 weeks of age. In the nude as well as in the heterozygous mice an age-related shift was observed in the localization of the C-Ig cells. In young mice of both groups the majority of these cells resided in the spleen, whereas in adult and old mice the bone marrow was found to be the major C-Ig cell organ, indicating that this shift is not dependent on the presence of the thymus. In young and adult nude and heterozygous mice C-Ig cell numbers in the spleen were comparable, whereas C-Ig cell numbers in the other lymphoid organs were higher in the heterozygous mice than in the nude mice. The total C-Ig cell number in young and adult nude mice was lower than in heterozygous mice of the same age, whereas in old nude mice they were as high as in heterozygous mice of the same age, indicating a retarded development of the immunological activity in nude mice. C-Ig cells in nude mice were almost exclusively of the IgM class, although in the bone marrow of the oldest animals also a substantial number of C-IgG and C-IgA cells was observed. Our finding that nude mice can live up to at least two years of age indicates that the age-related deterioration of the thymus-dependent limb of the immune system is not the cause of ageing, but rather a consequence of it.