Influence of age on the immunological activity and capacity of the CBA mouse.

The immunological activity and capacity were studied in the CBA mouse as a function of its age. The activity was determined by the number of immunoglobulin containing (C-Ig) cells in different lymphoid organs and the immunoglobulin levels of the serum in non-artificially stimulated animals. It was confirmed that in older age the bone marrow takes over from the spleen the role of the major site of immunoglobulin production. A clear decrease in the number of C-Ig cells was observed in the mesenteric lymph nodes and the Peyer's patches. The Ig serum remained constant after the sixth month of age, with the exception of an increase of IgG1 and IgG,2B. There was a striking increase in variation between the individual animals with advancing age. From these data it can be concluded that the B-cell system of old animals is as active as that of young adult animals. The immunological capacity of CBA mice of various ages was assessed by measuring the levels of specific antibodies after the administration of human serum albumin in complete Freund's adjuvant. A severe decline of the primary and the secondary response was observed on ageing. The reaction of three year old animals was negligible. The discrepancy between the declining immunological capacity and the constant or increasing immunological activity is explained by an age-related deficiency of the T-cell compartment in the spleen.