Ontogeny of RES Function in Birds

The chicken has served as an exquisite experimental animal model for investigating the functional ontogeny of the immune system. A major advance in immu-nobiology, to which the developing chicken has contributed to our present understanding, is that there are two distinct pathways for the differentiation of lymphoid cells. The first insight into this began with the fortuitous observations by Glick and his colleagues (Chang et al., 1955) showing that the removal of the bursa of Fabricius shortly after hatching resulted in profound impairment of the chicken’s ability to produce antibody following antigenic stimulation. Likewise, Cooper et al. (1965) demonstrated that, as had been seen in rodents (Good et al., 1962; Miller 1961), there was a loss in the ability of chickens to generate cell-mediated immunity following thymectomy at hatching. Thymectomy, however, had little effect on antibody production. Extension of these observations led Warner and Szenberg (1962) and Cooper et al. (1965, 1966) to propose that the lymphoid system could be dissociated on the basis of ontogenetic criteria into a bursa-dependent compartment which gives rise to antibody-secreting cells, and a thymus-dependent compartment which gives rise to cellular immune functions.