Antithymic antibodies in schizophrenic sera

Sera from normal controls and schizophrenics were examined for antithymic activity, employing a cytotoxicity test with C3H mouse thymocytes. The average level of antithymic activity in schizophrenics was considerably higher than that of controls, i.e., 50.3 +/- 27.1 (n = 54) and 35.3 +/- 19.5 (n = 33), respectively (p less than 0.01), in a fourfold serum dilution. The antithymic activity in newly admitted unmedicated patients was not statistically different from that of hospitalized medical patients. There was no difference in antithymic activity within the subdivisions of schizophrenia, such as hebephrenic, catatonic, and paranoid types. The antithymic titer also did not correlate with the psychopathological status as assessed by the BPRS total score. The antithymic activity against C3H mouse thymocytes in both the schizophrenic and control sera was completely adsorbed with mouse brain tissue homogenate (where Thy-1 antigen was present) and liver homogenate (where Thy-1 was absent), but not with human brain and liver. It seems unlikely therefore that antithymic factor in human sera contains antibodies against Thy-1 (brain-associated thymic) antigen. Antithymic activity is not considered specific for schizophrenic illness, and the high antithymic activity found in schizophrenics might be produced against unknown xenoantigens, probably as a result of a nonspecific dysfunction of the immunological system in such patients.