Ontogeny of the dendritic, and follicle-associated epithelial cells in thebursa of Fabricius of guinea fowl (Numida meleagris).

A panel of monoclonal antibodies was produced to study the mesenchymal stro mal. elements of the bursa of Fabricius in guinea hen. The intracellular an tigens recognized by GIIF3 and NIC2 monoclonal antibodies are of 50 and 30 kD, respectively. The cells identified by these antibodies emerge in the me senchyme around day 12 of incubation, and immigrate into the surface epithe lium of the bursal folds, which precedes the follicle formation. The GIIF3 cells move up to the luminal surface of the follicle and differentiate to f ollicle-associated epithelial cells. The NIC2 cells remain in the medulla, produce and secrete large amount NIC2 positive substance, when the bursal f unction starts up. The presence of double positive (GIIF3 and NIC2) cells i n the medulla around hatching, seems to indicate, that the two cells might have a common origin. The NIC2 positive product of the bursal secretory den dritic cells contributes to the microenvironment, and possibly necessary fo r the B cell clonal expansion and establisment of the immune repertoire in the guinea hen.