Immunoreactions involving platelet. VI. Reactions of maternal isoantibodies responsible for neonatal purpura. Differentiation of a second platelet antigen system.

Although there is some evidence that neonatal thrombocytopenic purpura, which occurs in otherwise normal children born of healthy mothers, is caused by maternal antibodies formed against fetal platelets (1-3), lack of reliable serologic techniques generally has prevented convincing demonstration of the responsible antibodies and has precluded thorough investigation of the properties and inheritance of specific platelet antigens presumed to be involved. Because experience in this laboratory has shown that complement fixation is the most sensitive technique for detecting several different types of antiplatelet antibodies (4-6), this technique was applied in a search for antibodies in the sera of normal mothers who had given birth to thrombocytopenic infants. In the present report the isoantibodies which were found are characterized, and the sensitivity of the complement fixation technique is compared with that of other techniques employed in attempts to detect antiplatelet antibodies.