In vitro immunoglobulin productive and proliferative responses to pokeweed mitogen by peripheral blood lymphocytes from old individuals

The purpose of this investigation was to compare T and B cell functions between old individuals over 70 years of age and young under 35 years.Peripheral blood lymphocytes from each age group were subdivided into T cell enriched and B cell enriched fractions. Immumoglobulin (Ig) production by the lymphocytes, which were mixtures of T and B cell fractions derived from the two groups, was assessed by measuring IgG secreted into the medium after 8 days culture in the presence of various concentrations (0-20μl/ml) of pokeweed mitogen (PWM). IgG production by combinations of “young” T cells/“old” B cells was less than by “young” T cells/“young” B cells combinatiions. Combinations of “old” T cells/ “old” B cells secreted a smaller amount of IgG than “old” T cells/“young” B cells combinations. The results indicate an impaired IgG production by “old” B cells in response to PWM.At high concentration of PWM (5-20μl/ml), IgG production was greater in “old” T cells/“young” B cells combinations compared to “young” T cells/“young” B cells combinations, suggesting either an incresed helper or decreased suppressor activity of the “old” T cells.Proliferative responsiveness to PWM was compared between “old” and “young” B cells cultivated with mitomycin-C (MMC) treated T cells from either group by measuring 3H-thymidine uptake after 4 days of culture. “Old” B cells always showed a lower uptake of 3H-thymidine than “young” counterparts, when both B cells were cocultivated with either “old” or “young” MMC treated T cells. Furthermore, a significant correlation was found between 3H-thymidine uptake and IgG production in cultures of MMC treated T cells/B cells combinations in the presence of PWM at 1μl/ml. These results suggest that impaired Ig production by “old” B cells stimulated by PWM would be ascribable to defective earlier steps of proliferative response of “old” B cells themselves.