Aging increases expression of LPS-induced autoantibody-secreting B cells.

Escherichia coli lipopolysaccharide (LPS), a polyclonal B cell activator, has been employed to achieve in vitro stimulation of autoantibody-secreting B cells in young adult and aged mice of long-lived strains as assayed in a hemolytic plaque technique to syngeneic mouse erythrocytes. Aged 21- to 24-month-old C57BL/6J and (C57BL/10Sn x C3H/HeDiSn)F1 mice were found to express 3 to 4 times as many LPS-induced plaque-forming cells (PFC) to autologous erythrocytes than did younger 6-month-old animals. With the use of cyclophosphamide (CY), a significant enhancement of auto-PFC production in young mice occurred, approaching levels found in non-CY-treated old mice. Thus, autoreactive clones of lymphocytes exist in the spleens of young adult mice, but under normal circumstances produce little autoantibody. The situation in aged members of these strains, therefore, does not seem to involve an actual increase in numbers of autoreactive B cells, but may possibly involve some form of deregulation, permitting increased age-related expression of autoreactive lymphocyte clones.