Direct stimulation of lymphoid tissue of the chicken. 3. Haemagglutinin production, haemolysin-forming cells and changes in lymphoid tissues following injection of guinea-pig erythrocytes into the bone marrow.

The hypothesis that the avian bone marrow is a site of actual antibody production has been experimentally verified in this study. Normal and neonatally bursectomized 8-week-old White Rock chickens were injected with guinea-pig red blood cells into the left femoral marrow or into the wing vein. The intramarrow administration of antigen proved to be as effective as the intravenous injection in inducing the production of haemagglutinins and antibody plaque response of 19S class. An important finding was that White Rock bursaless chickens were capable of synthesizing considerable amount of circulating 19S agglutinin after a single challenge with guinea-pig erythrocytes. There was a significant proliferation of plaque-forming cells in the spleen and bone marrow of normal immunized chickens. Quantitative cytological analysis revealed that an increase in the number of small and immature lymphocytes preceded the appearance of cells of the plasmacytic series in both antigen-injected marrow and contralateral non-injected marrow. The thymus and bursa did not exhibit apparent changes. This study provides strong evidence that chicken bone marrow may act in antibody production as a secondary lymphatic tissue. The results are discussed with respect to the interaction between thymus-derived, bursa-derived and bone marrow-derived cells in humoral immunity of the chicken.