The lymphoid substance of the chicken's Harderian gland is organized in two histologically distinct compartments

Abstract

Light and electron microscopical investigations revealed that the lymphoid structure of the chicken Harderian gland is organized in different histological frameworks. In the head the surface epithelium of the central canal can be classified as a lymphoepithelial tissue which covers the dense lymphoid substance. It consists of small and medium-sized lymphocytes, dendritic-like cells, and occasional macrophages. High endothelial venules are associated with intense lymphocyte migration and homing that gives circumstantial evidence for a T-dependent region, as found in a secondary lymphoid organ. The B-dependent germinal centers are also common structural units of the head region's lymphoid substance. The body of the gland is loaded with plasma cells of different maturation stages. They immigrate into the epithelium of the central canal and produce IgM and IgA. Only a few scattered IgG producing plasma cells can be found in the gland of Harder. This plasmocytic region accounts for the immunosurveillance on the conjunctiva and in the upper respiratory tract through antibody production against bacterial or parasitic infections. In both the head and body regions of the gland, anti-B-L (anti-Ia) antibody recognized scattered elongated cells which might represent dendritic cells. The immunological relationship between the two histologically different parts of the Harderian gland is unknown, but we speculate that the dense lymphoid tissue with high endothelial venule receives the blood-borne, immunologically mature, but uncommitted B cells. By the influence of local antigen stimulus, these B cells transform to plasma cells which gradually appear in the body of the gland. The lymphoid structures of the head and the body fulfill the function of secondary and tertiary lymphoid organs, respectively.

Age-related development and tissue distribution of T cell markers (CD4 and CD8a) in Chinese goose

“…As the eye-associated or the skin-and pineal-associated lymphoid tissues, the further maturation of HG is antigen driven (Olah et al, 1996). Also HG is the only lymphoid tissue that open to the surrounding antigen.…”

Intraepithelial plasma cells in the avian copulatory organ of two tinamou species: quantitative variation during the breeding season

“…This intraepithelial localization of plasma cells is a finding that should not be neglected, considering that, although quite limited, this occurrence has already been reported in different organs of specimens of most representative groups of Tetrapoda (Bang and Bang 1968;Lefevre et al 1973;von Rauntenfeld et al 1976;Chin and Wong 1977;Schramm 1980;Solas and Zapata 1980;Olµh et al 1992;Nickerson et al 1984). The role of these cells is still not clear, but their intraepithelial position can be indicative that a direct contact between plasma cells and epithelial cells may render the antibodies more accessible for transport through the epithelium (Nickerson et al 1984;Olµh et al 1996). The function of the fixed tubular portion is that of mucus secretion for lubricating and facilitating the phallus eversion at copulation (Komµreck and Marvan 1969).…”

“…In this sense, it may not be just coincidence that, similar to the phallus, abundant intraepithelial plasma cells were found in Harderian glands only in birds among the vertebrates. As stated by Olµh et al (1996), the lack of secondary lymphoid organs may influence the development of the tertiary lymphoid organ, such as the Harderian gland. Taken together, these facts may indicate that migration of plasma cells into the epithelium is more common in birds than we can presently predict.…”

The Avian Respiratory Immune System

“…Briefly, the glandular lymphoid tissue is organized in two histologically distinct compartments [15], in which the lymphoid structure in the head of the gland, with its follicle-associated epithelium (FAE), high endothelial venules (HEV) and germinal centers (GC), represents a BALT-like secondary lymphoid organ, while the plasma cell-filled body resembles a tertiary lymphoid structure, maintaining classical immunosurveillance. A detailed description of its anatomical structure can be found in Chapter 2.…”