Characterization of the immunosuppression accompanying virus-induced avian osteopetrosis.

Infection of chickens with a myeloblastosis-associated virus which induced a high incidence of osteopetrosis was accompanied by immunosuppression. The immunosuppression was manifested in the following ways. The weight of the bursa, spleen, and thymus was depressed in infected chickens. Infected animals had a diminished capacity to form hemolytic plaques in a direct assay. Spleen cells from osteopetrotic animals did not respond to phytohemagglutinin, and the spleen and bursa had a decreased proportion of cells possessing surface immunoglobulin. Osteopetrotic animals failed to show an age-dependent increase in the proportion of cells demonstrating surface immunoglobulin that was observed in normal animals. However, several individual chickens with heavy osteopetrosis responded to antigenic stimulation in a normal fashion, indicating that although immunosuppression usually accompanies avian osteopetrosis, it may not contribute directly to abnormal bone proliferation.