Antibodies selectively reactive to autologous and host-type platelets are obtained following interspecies immunizations in marmosets.

Interspecies immunization of marmosets with platelets leads to an acute thrombocytopenia which appears to be immunologically mediated. The thrombocytopenia is preceded by the formation of antibodies to the donor platelet antigen and deposition of IgG on the host's platelets. Examination of sera obtained from these animals during the course of the disease has revealed the presence of antibodies towards autologous and host-type platelets. Autologous antibody was found when thrombocytopenia was severe; upon platelet recovery, this antibody was absent or reduced in titre. This in vivo absorption of host-specific (autologous) antibody led to detection in the serum of antibodies reactive to other members of the host species. The presence of such host-type antibodies appeared to be related to the intensity of antigenic stimulation, the amount of antibody formed and the degree of thrombocytopenia. Deposition of IgG on the host's platelets coincided with the appearance of the anti-host antibodies; whether the IgG detected on the host's platelets is exclusively cross-reactive antibody or includes also an immune complex is not yet known. Finally, the data have identified potential immunogenetic differences among members of two marmoset species with respect to platelet antigens.