Development and Distribution of Immunoglobulin-Containing Cells in the Chicken

Abstract

The development and distribution of immunoglobulin-containing cells were studied in chickens using purified antibodies to µ, γ and light chains labeled with fluorochromes. Cells containing µ and light chains were found in lymphoid follicles of the bursa of Fabricius of 14-day embryos. IgG-containing cells were initially observed in bursal follicles at 21 days of incubation. Embryonic infusions of plasma from newly hatched and adult chickens had no effect on the appearance of immunoglobulin-containing cells within the bursa. The developmental sequence of immunoglobulin-containing cells within the bursa was later recapitulated in the spleen, tonsilla caecalis and thymus. Rapid expansion of IgM- and IgG-containing cells began in the spleen on the 3rd and 8th days, respectively, after hatching. The ratio of IgG- to IgM-containing cells was greatest in the intestinal wall of immunologically mature birds. Development of immunoglobulin-containing cells in extra-bursal sites was retarded in chickens hatched under germ-free conditions. In contrast, neither exclusion of exogenous antigens nor antigenic stimulation in ovo affected the time of appearance or proliferation of immunoglobulin-containing cells within the bursa. The medullary regions of individual bursal follicles frequently stained for both IgM and IgG. This pattern was not observed in lymphoid follicles of other tissues. Analysis of single cell suspensions revealed a high proportion of single bursal cells containing heavy chains of both IgM and IgG, wheras spleen cells rarely contained both classes of immunoglobulins. The results suggest that a developmental switch from IgM to IgG synthesis may occur within the bursa.