The production of antibody by bursal lymphocytes

Lymphocytes of the bursa of Fabricius have been found to bind actively an enteric form of E coli resulting in the formation of bacterial adherence colonies (BAC). The absolute number of binding lymphocytes appears to increase as the chicken reaches sexual maturity. Treatment of bursal cells with antichicken immunoglobulin results in the blocking of BAC formation. Furthermore, a modified plaque assay technique reveals that a portion of the bursal lymphocyte population is actively secreting antibody against the flagella of E. coli. Introduction of antigen into the cloacal lumen does not appear to significantly affect circulating antibody levels. Therefore, these data suggest that an additional functional role of the bursa after hatching is localized immunologic defense of the organism.