THE IMMUNOGENETICS OF IMMUNE SENESCENCE

Immune senescence is characterized by a dysregulation of the immune sy stem. With respect to humoral immunity, aging is associated with an in creased level of many autoantibodies and a decreased antibody response to most foreign antigens. This observation reflects a decreased capac ity to activate antibody production by CD5-negative B cells despite a normal or increased capacity to generate antibodies produced by the CD 5-positive B cells. A similar dysregulation of cell-mediated immunity is manifested by an altered balance in cytokine production by T cells from old as compared to young subjects. Thus, the production of interl eukin-2 (IL-2), IL-3 and granulocyte-macrophage colony-stimulating fac tor by T cells from old subjects is decreased although the production of IL-4, IL-5 and IL-6 is undiminished or actually increased.