Age-decrease of cells sensitive to an autoantibody-specific for thymocytes and thymus-dependent lymphocytes in NZB mice.

NZB mice naturally produce an autoantibody which in the presence of complement is specifically cytotoxic for thymocytes and thymus-dependent lymphocytes (T-cells) in the peripheral lymphoid tissues (lymph nodes and spleen) and the circulation of mice. Using a direct cytotoxicity test with a NZB mouse serum pool which contained the high titred autoantibody, a progressive decrease was observed with age in the proportion of the autoantibody-sensitive cells in mesenteric lymph node, spleen, and blood of NZB mice in comparison with mice of other strains (C57BL/6J and NZW). The numerical decrease in the population of autoantibody-sensitive cells was evident at younger age and greater degree in the peripheral blood than in the lymph node and spleen. The age-decrease in the number of autoantibody-sensitive cells in lymph node and spleen contrasted with the numerical increase in nucleated cells in these organs. The age-decrease in the proportion and number of the autoantibody-sensitive cells in the blood exceeded the decrease in the blood lymphocyte count. This finding indicated that T-cells in the blood are selectively depleted with the ageing of NZB mice. A similar observation was made on the blood lymphocytes of (NZB × NZW)F1 hybrid mice. The depletion of T-cells in the blood in association with the production of natural thymocytotoxic autoantibody is termed autoimmune thymus-dependent lymphocytopenia.