Platelets from schizophrenic patients bear autoimmune antibodies that inhibit dopamine uptake

Platelet-associated antibodies (PAA) from schizophrenic patients and healthy individuals were determined by conventional enzyme immunoassay. The platelets of the schizophrenic patients were found to carry notably higher levels of PAA than were those of the healthy controls. PAA from the schizophrenics inhibited specifically the uptake of dopamine (DA) by platelets. The DA uptake by normal platelets could be reduced to a level similar to that observed in platelets of schizophrenics upon binding of PAA from schizophrenics. Serotonin uptake was virtually unaffected by these antibodies. The Vmax value of dopamine uptake by platelets of schizophrenics was similar to that for normal platelets treated with PAA of schizophrenics, as well as that for normal untreated platelets. However, the Km values of the uptake were higher in the platelets from schizophrenics and normals treated with PAA from schizophrenics than in the untreated platelets of normals. PAA from schizophrenics were found to bind to rat brain P2m membranes and to interfere with the binding of the dopamine receptor ligands [3H]-dopamine and [3H]-spiperone. These results suggest that blood platelets may function as a peripheral epitope for the formation of PAA, which, when reaching the brain, may react with the dopamine receptor and elicit mental disorder.