Antibody‐producing Cells in Antigenically Stimulated Mammary Glands and in the Gastro‐intestinal Tract of Sheep

Summary The histological changes in normal mammary glands of ewes during the period one month before and after lambing have been compared with the changes occurring in glands infused with antigen one month before lambing. Attention was focused on the changes in concentration and on the location of cells of the lymphocyte‐plasma cell and macrophage‐monocyte series. The most significant feature following antigen infusion was the striking appearance of pyroninophilic cells usually situated in areas adjacent to the glandular epithelium. Lymphocytes were also more numerous in infused than non‐infused glands until early lactation. Attempts were made to detect specific immunoglobulin‐producing cells in mainmary glands, certain other glandular tissues and in lymph nodes. When sections of infused mammary glands were stained with specific antisera conjugated with fluoresce in isothiocyanate numerous fluorescing cells were observed and their location correlated closely with that of the pyroninophilic cells seen in paraffin sections. The majority of the fluorescing cells were of IgA‐specificity with IgG1‐ and IgM‐specific cells present in lower concentrations. In the gastro‐intestinal tract fluorescing cells located in the lamina propria were abundant and the majority were IgA‐specific. Numerous IgG1‐ and IgG2‐specific cells were present in the lymph nodes. Very few pyroninophilic or flourescing cells were seen in sections of the parotid salivary gland, uterus and vagina. The observations indicate that the majority of pyroninophilic cells in antigen stimulated mammary glands and in the gastro‐intestinal tract are IgA‐specific cells which are responsible for the local production of antibody.