Histology and immunology of Peyer's patches in the domestic fowl (Gallus domesticus).

Peyer's patches (PP) were identified in the small intestine of the domestic fowl by their thickened villi, flattened epithelium which lacked goblet cells and by the accumulations of lymphocytes in the form of encapsulated germinal centres (GC) and diffuse lymphoid tissue (DLT). Particles of orally administered carbon were seen in GC and DLT, in macrophages and within epithelial cells (M cells). Faults in the PP epithelium, which was positive for alkaline phosphatase, allowed the extrusion of lymphocytes into the intestinal lumen. Immunofluorescence detected more lymphoid cells with cytoplasmic IgG than IgA or IgM. Specific antibody production was seen in cells of GC ad DLT in PP from fowls that had received multiple injections of horse serum.