Lymphocyte subpopulations in high endothelial venules and lymphatic capillaries of bronchus‐associated lymphoid tissue (BALT) in the rat

Abstract

The subpopulations of lymphocytes and non-lymphoid cells in high endothelial venules (HEV) and in lymphatic capillaries surrounding lymphoid follicles in bronchus-associated lymphoid tissue (BALT) were examined by electron microscopy after preembedding the tissue and staining with an immunoperoxidase technique. The results were compared with those obtained in gut-associated lymphoid tissue (GALT) reported previously. Monoclonal mouse-anti-rat T cell, IgG, IgM, IgA, and Ia antisera were used. Plasma cells that were reactive to anti-IgG, anti-IgM, and anti-IgA were detected as cells in which the 3',3'-diaminobenzidine tetrahydroxychloride reaction product was localized in rough endoplasmic reticulum and perinuclear spaces but not on plasma membranes. These plasma cells did not occur in either lymphatic capillaries or HEV in BALT as they did in GALT. Cells with surface Ig (sIg cells), T-cell antigen (T cells), and Ia antigen (Ia cells) were present in BALT. T cells were located predominantly in the follicular area opposite the bronchial epithelium; IgM- and IgG-reactive cells were found in the follicular area adjacent to the bronchial epithelium; and IgA-positive cells were found in the lateral part of the area where the T cells were localized (T-cell area). Ia cells were abundant throughout BALT and in moderate numbers in the epithelium. A striking observation was the presence of "nurse-cell"-like structures in the periphery of BALT. The percentages of T, sIgG, sIgM, and sIgA cells in the HEV were 54.7%, 2.4%, 28.9%, and 27.3%, respectively, and in the lymphatic capillaries, 41.2%, 3.8%, 38.2%, and 21.2%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte Subpopulations in Mediastinal Milky Spots of Mice: Light- and Electron-Microscopic Immunohistochemical Observations.

“…Gut-associated lymphoid tissues (GALT) and Table 1. Percentages of cells (mean+standard deviation) labeled with various antibodies in the mediastinal milky spots of mice bronchus-associated lymphoid tissues (BALT) are always exposed to the exogenous antigens through the epithelium, and the structure of these tissues are in some respects similar to that of lymph nodes: the presence of a germinal center, HEV in the T cell area and lymphatic capillaries around the lymphoid tissues (SMINIA and PLESCH, 1982;BREEL et al, 1988;OTSUKI et al, 1988OTSUKI et al, ,1989a. On the other hand, mediastinal milky spots as well as fallopian tube- (OTSUKi et al, 1989b) and uterus-associated lymphoid tissues (OTSUKI et al, 1990) are normally under aseptic conditions and possess common structures such as the absence of a germinal center, HEV and lymphatic capillaries, the presence of only a few plasma cells and many lymphocytes and macrophages migrating between epithelial cells.…”

“…The percentage of lymphocyte subsets was characteristic in MALT. The major lymphocyte subsets were IgG-and IgM-positive cells in mouse mediastinal milky spots, T cells, IgA-and IgM-positive cells in rat GALT (OTSUKI et al, 1988), pan T cells in rat BALT (OTSUKI et al, 1989a), and suppressor T cells in human fallopian tube-and uterus-associated lymphoid tissues (MORRIS et al, 1986;OTSUKI et al, 1989b;OTSUKI et al, 1990). It remains to be determined if the variety of major lymphocyte subsets among these lymphoid tissues is caused by different exogenous antigens coming to the surface of the lymphoid tissues, or by organ-specificity or species difference.…”

Bronchus-Associated Lymphoid Tissue (BALT) Is Not Present in the Normal Adult Lung but in Different Diseases

“…As there are no afferent lymphatics, these HEV are the only entry site for lymphocytes to migrate into the BALT [12,13]. The follicles are also partly surrounded by lymphatics filled with lymphocytes which are on their way to the draining lymph bronchial lymph node [12]. In the direction of the bronchial epithelium, a dome-like protrusion (similar to Peyer's patches) into the bronchial lumen is sometimes obvious.…”

“…In the walls of the HEV, lymphocytes can be seen leaving the blood and thus entering BALT. As there are no afferent lymphatics, these HEV are the only entry site for lymphocytes to migrate into the BALT [12,13]. The follicles are also partly surrounded by lymphatics filled with lymphocytes which are on their way to the draining lymph bronchial lymph node [12].…”

Stimulation of Bronchus-Associated Lymphoid Tissue in Rats by Repeated Inhalation of Aerosolized Lipopeptide MALP-2

“…In BALT, a germinal center is often found. The lymphocytes enter the BALT from the blood via the high endothelial venules and leave via lymphatics [2]. An overlaying epithelium infiltrated by lymphoid cells may play an important functional role in antigen uptake and induction of a specific immune reaction [3][4][5][6][7].…”