Thymocytotoxic autoantibodies found in mice infected with Schistosoma japonicum

Thymocytotoxic autoantibodies were demonstrated in sera of C3H/HeJms, C57BL/6J, and ddY mice infected with 50 cercariae of Schistosoma japonicum, using C57BL/6J thymocytes as target cells in the trypan blue dye exclusion test. Kinetic study revealed that thymocytotoxic activity began to increase at week 6 of infection, reached a maximum at 8 weeks, and thereafter decreased gradually. Thymocytotoxic antibodies had an optimal reactivity at 4 degrees C and were sensitive to 2-mercaptoethanol treatment, suggesting that they were immunoglobulin M in nature. The cytotoxicity was completely abolished by absorption with C57BL/6J thymocytes but not with S. japonicum parasites or eggs. The antigen reacting with thymocytotoxic antibodies was found in the thymus, brain, spleen, and, to a lesser extent, kidney and liver. In parallel with the appearance of thymocytotoxic antibodies, the increase of background plaque-forming cells to trinitrophenyl, polyvinyl pyrrolidone, and sheep erythrocytes in the spleen of S. japonicum-infected mice suggested that te induction of thymocytotoxic antibodies may be the consequence of polyclonal B-lymphocyte stimulation by the infection.