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antigenic stimulation with inactivated Salmonella pullorum or dinitrophenyl-bovine gamma globulin. The mycoplasma-infected groups had significantly lower antibody responses to both antigens. The suppression was more evident in the secondary response. The results suggest that the immune response of turkeys infected with M. meleagridis is similar to that of bursectomized chickens: the ability of chickens to synthesize immunoglobulin G is affected more readily than the ability to synthesize IgM.

The suppressive effect of Mycoplasma gallisepticum (MG) on Haemophilus gallinarum (HG) immune response was shown. Antibody response to HG was highly suppressed when chickens were inoculated intramuscularly with HG-MG combined bacterin. Findings were similar in chickens injected intramuscularly with HG and MG bacterin separately at adjacent sites. No immunosuppressive effect was recognized when injections with HG and MG bacterins were in the left and right thigh muscles, respectively, or from intravenous inoculation with the combined bacterin. Nor did HG-Mycoplasma synoviae (MS) combined bacterin injected intramuscularly evidence immunosuppression. Recovery rate of HG and clinical symptoms were more evident in chickens with suppression of antibody responses than in chickens without suppression.

The recent interest in the immunosuppressive effect of early infection with infectious bursal disease virus (IBDV) in chicks without maternal antibody has raised questions of how susceptible breeding flocks can be immunized. Uniform infection and immunization of adults is desirable if chicks are to be protected by passive transfer of maternal antibody from the dam through the egg. Two previous attempts (1) to infect adult birds by ocular administration of virus gave negative results in one case and positive results in the other.