Characterization of the Conjunctiva-Associated Lymphoid Tissue (CALT) in The Buffalo (Bubalus bubalis)

CALT plays an essential role in ocular and systemic immunity, it was investigated in different species but not yet in the buffalo. Therefore, fresh eyes with their eyelids were collected from 7 clinically healthy adult buffaloes (2-5 years) and investigated using histological, histochemical, immunohistochemical and ultrastructural techniques. The CALT was formed from lymphoid nodules and internodular diffused lymphocytes and some plasma cells localized in the lamina propria. The CALT was associated with high endothelial venules and lymphatics. The lymphoid nodules contain follicular dendritic cells among the lymphocytes. CALT-associated epithelium was free from goblet cells and rich in M cells. Intraepithelial lymphocytes were frequently observed forming lymphoepithelium. CD3 positive T lymphocytes were observed in the CALT-associated epithelium, within the germinal centre and mantle zone. They were also found in the internodular areas and within lymphatics. The current findings indicate the possible active immunological role of CALT represented in sampling of antigen by M cells, recognition of antigen by dendritic cells and lymphocytes and finally initiation of immune reaction. All this is supported by lymphocyte recirculation through the high endothelial venules and lymphatics.