Age-related changes in the cellular immune response of lymph node and thymus cells in long-lived mice.

Relative capabilities of lymph node and thymus cells from (C57BL/6J) × Balb/cJ) F₁-hybrid mice and from (C57BL/6J × 129J)F₁—hybrid mice 6, 20, and 30 mo of age to respond in the mixed lymphocyte reaction were assessed. Both the direct response and the ability to synergize with partner lymph node or thymus cells were studied. Lymph node cells demonstrated an age-related decline both in responding directly to stimulation by allogeneic cells, and in ability to synergize with syngeneic thymocytes. Thymus cells showed an age-related increase in response to direct stimulation, and no clear-cut age-related change in synergizing capability. In these long-lived mouse strains at least one cause of the age-related decline in cellular immunity relates to developing deficiencies in the recirculating lymphoid pool, probably T₂ cells.