Antibody-mediated immuno-regulation in chick embryos and baby chicks.

Two- and three-week old chicks that received at hatching serum from either unimmunized birds or from chickens immunized with bovine serum albumin responded with normal hemagglutinin titers to immunization with mouse erythrocytes (MRBC). Other chicks administered at hatching or as embryos with homologous serum high in anti-MRBC activity responded poorly to MRBC immunization. When donor serum samples collected on different days after immunization were tested, the immunosuppressive capacity was negligible the first two days, increased in potency thereafter to a maximum level by the end of the week. The increase with time in the inhibiting property of the donor serum paralleled the serum anti-MRBC hemagglutinin response profile. The immune capacity of the antibody-treated recipients was severely depressed for over two weeks. By the fourth week, however, the immune responsiveness to MRBC, as measured by serum hemagglutinin titers and production of antigen sensitive units, had recovered to near normal levels.