Antibody and immunoglobulin levels in aged humans.

IgM and IgG type antibody titers and levels of serum IgG, IgA and IgM were determined in healthy young and aged subjects. The proportion of subjects of low antibacterial agglutinin titers progressively increased during the 7th and 8th decades of life. Anti-streptolysin-O titers were also shifted to the lower values in aged subjects, at least until the 8th decade of life, although subnormal values compared to the young control range were less frequent than in the case of IgM type antibodies. Anti-streptokinase values did not seem affected by age. In contrast to antibody levels, serum IgM was similar or slightly higher in old compared to young subjects. Evidence is presented that the proportion of 7 S IgM drops with aging. Both IgA and IgG levels increased through the 7th, 8th and 9th decades of life. Different class immunoglobulin levels seemed to be considerably correlated and a tendency to correlate was found between IgG type antibody and serum IgG levels. Complex investigations including quantitation of antibodies to extrinsic and intrinsic antigens and serum immunoglobulins are proposed to define the humoral immune status of aged subjects and to understand the causes as well as the diagnostic and prognostic significance of old age 'imbalances'.

Alterations of two parameters of cellular immunity in the aged men.

There were two parameters of cellular immunity in 46 old and 34 adult (control) individuals investigated. These reactions were delayed type hypersensitivity of the skin and the in vitro leukocyte migration inhibition test. PPD was used as antigen for both reactions. According to our investigations there was no correlation between them neither in the aged nor in the control group. But the statistical analysis of data revealed a significant difference between skin responses of aged and control groups. In spite of this we consider cellular immunity unaltered in old men, because there was no difference in migration inhibition between aged and adult men and according to our earlier experiments in guinea pigs this test is much more reliable than skin response.

Natural antibody level in old age.

Antibacterial antibodies were determined with a passive hemagglutination micromethod using the Boivin extract of eight different strains of bacteria. Correlation between antibody values of different specificities and between the summarized titer values and individual antibody titers were found. A significant decrease in the average of the summarized titer values was observed especially for persons over 70. The possibility of genetic regulation of normal antibody levels is suggested. The question whether the decrease in agglutinating antibody level in old age is due to the decreased activity of the corresponding immunocompetent cells or is secondary to other changes occuring in old age, is discussed.