Histology, Histochemistry and Ultrastructure of the Gut-Associated Lymphoid Tissue in Large Intestine of Goats

Abstract

Gross, histological and scanning electron microscopic studies were conducted on the gut-associated lymphoid tissue (GALT) in the large intestine of six crossbred male goats of six months of age. GALT in large
intestine was distributed as solitary lymphoid nodules (SLNs) and patches in the large intestine, in the proximal colon (PC patch) and in the rectum (RC patch). Histologically, the lymphoid nodules in all the patches of large
intestine occurred in two morphologically different forms, viz. propria nodules and lymphoglandular complexes (LGC). In the case of propria nodules, the lymphoid nodules were seen mainly in the lamina propria and its dome projected into the lumen of the intestine. In the LGC, several lymphoid nodules were almost completely located under the muscularis mucosae in the tunica submucosa. The dome was covered by a follicle-associated epithelium (FAE). The diameter of the lymphoid nodules and number of lymphocytes per nodule were maximum in RC patch. In the FAE of GALT in large intestine, the UEA-I bound intensely to the apical membrane of M-cells. Presence of fine-granular alpha-naphthyl acetate esterase (ANAE) activity was seen in the cytoplasm of T-lymphocytes
and macrophages in the internodular area and mantle zone of the lymphoid nodules. In the immunohistochemical staining technique for detection of IgG bearing B-lymphocytes, stong positive reaction was noticed within the
germinal centre of lymphoid nodules. In scanning electron microscopy of GALT in the large intestine, the rounded sac-like follicles were the largest in the RC patch. Maximum development of lymphoid tissue was noticed in the rectal patches, suggesting that they could be exploited as targets for rectal vaccines for the induction of mucosal immune response in this species.