title: Decreased in vitro humoral immune responses in aged humans.
abstract: Induction of antigen-specific and non-specific (polyclonal) humoral immune responses in vitro was investigated in peripheral blood mononuclear cells of aged (65-85 yr) and young (20-30 yr) volunteers. In vitro immunization of lymphocytes with antigen (sheep erythrocytes) was performed in a recently described microculture system, and anti-sheep erythrocyte plaque forming cells were quantitated in a direct hemolytic plaque assay. Immunoglobulin secreting cells, induced polyclonally with pokeweed mitogen, were quantitated in a reverse hemolytic plaque assay. Significant depressions of antigen-specific as well as polyclonal responses were noted in relation to advancing age. Antigen-specific responses were more frequently depressed than polyclonal responses. T cell mitogen concanavalin A (Con A) was used to amplify functions of autologous immunoregulatory T cells. Addition of 10 microgram/ml Con A to lymphocytes of young donors at culture initiation resulted in activation of suppressor cells and abrogated antigen-specific responses. Delayed addition of Con A, on the other hand, enhanced responses, presumably because of activation of helper T cells. Similar manipulations of lymphocyte cultures from aged donors showed failure of Con A to suppress antigen-specific responses in approximately half of the responders. In many nonresponders, responses within normal range were elicited by the delayed addition of Con A to their lymphocyte cultures. Deviations beyond the range of expected responses were noted in 32.5% of the co-cultures between pokeweed mitogen stimulated young and aged cells. Our findings suggest that age-related deficiencies of B cell function are frequently associated with dysfunction of immunoregulatory T cells and are only occasionally due to intrinsic defects of B cells.
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D000917:Antibody Formation; D000918:Antibody Specificity; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D005260:Female; D006462:Hemolytic Plaque Technique; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011043:Pokeweed Mitogens / Q000494:pharmacology; D013997:Time Factors
chemical_list: D007136:Immunoglobulins; D011043:Pokeweed Mitogens; D003208:Concanavalin A