The vascular-associated lymphoid tissue: a new site of local immunity

Acquired immunity is orchestrated in various lymphoid organs, including bone marrow, thymus, spleen, and lymph nodes in humans. However, mucosa-associated lymphoid tissue (MALT) is evolutionally known to be emerged in the oldest vertebrates as an immunological tissue for acquired immunity, much earlier than the advent of lymph nodes which appeared in endotherms. Furthermore, the lymphocytes which developed in MALT are known to circulate within the limited anatomical areas. Thus, MALT is comprehended as not the structure but the immune network dedicated to local immunity. As for the skin, skin-associated lymphoid tissue (SALT) was previously postulated; however, its existence has not been proven. Our group recently showed that aggregations of dendritic cells, M2 macrophages, and high endothelial venules (HEVs) are essential components to activate effector T cells in the murine contact hypersensitivity model and termed it as inducible SALT (iSALT) since it was a transient entity that serves for acquired immunity of the skin. Furthermore, in various human skin diseases, we reported that the ectopic formation of lymphoid follicles that immunohistochemically analogous to MALT and regarded them as human counterparts of iSALT. These data raised the possibility that SALT can exist as an inducible form, namely iSALT, which shares the biological significance of MALT. In this article, we revisit the evolution of immunological organs and the related components among vertebrates to discuss the conserved functions of MALT. Furthermore, we also discuss the putative characteristics and functions of iSALT in the context of the MALT concept.

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Dynamics of quantitative changes of diffuse lymphoid tissue cells of bronchi and lungs of guinea pigs sensitized with ovalbumin

Morphologia ◽

10.26641/1997-9665.2021.2.53-58 ◽

2021 ◽

Vol 15 (2) ◽

pp. 53-58

Author(s):

S.S. Popko ◽

V.M. Yevtushenko

Keyword(s):

Immune System ◽

Respiratory System ◽

Guinea Pigs ◽

Lymphoid Tissue ◽

Plasma Cells ◽

Early Period ◽

Allergic Inflammation ◽

The Body ◽

Local Immunity ◽

Experimental Group

Background. There is a progressive increase of respiratory allergic diseases nowadays in the world, made it necessary to study the participation of the components of the immune system in these processes. From the point of view of modern aspects about the organs of the immune system, interesting are the patterns of morphogenesis and function of bronchus associated lymphoid tissue, occupied a special place in the immunological protection of the body due to the large area of contact with various antigens. Morphogenesis and reactive changes in the local immunity in respiratory system in conditions of allergic inflammation remain urgent issue of modern morphology. Objective. To study the changes in diffuse lymphoid tissue of bronchi and lungs of guinea pigs sensitized with ovalbumin. Methods. We have studied the lung of 48 guinea pigs, using histological, immunohistochemical, morphometric, statistical methods, under conditions of experimental ovalbumin-induced allergic inflammation, assessed the average number of lymphocytes, macrophages and plasma cells in the diffuse lymphoid tissue. Results. The average number of lymphocytes in diffuse lymphoid tissue of bronchi and lungs increased from the 23rd day of observation and remained at a high level until the end of the experiment, the maximum was during the early period of the development of allergic inflammation, the increasing coefficient was 4.7. The average number of plasma cells also acquired maximum elevation in the early period of allergic process, the increasing coefficient was 2.0. The most significant average number of macrophages was on the 23rd day of observation with same increasing coefficient. Among all types of immunocompetent cells of diffuse lymphoid tissue in bronchi and lungs, T-lymphocytes prevailed during the experiment elevated almost by 5 times. Conclusions. In the early period of development of experimental ovalbumin-induced allergic inflammation, the specific resistance of the respiratory system manifests itself in the form of activation of local links of cellular and humoral adaptive immunity, as evidenced by the dynamics of changes in the average number of lymphocytes (the maximum increasing coefficient 4.7 in the 1st experimental group), macrophages and plasma cells (maximum increasing coefficient 2.0 in the 1st experimental group) of diffuse lymphoid tissue of bronchi and lungs of guinea pigs.

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Ontogeny of the Local Immune System

PEDIATRICS ◽

10.1542/peds.64.5.765 ◽

1979 ◽

Vol 64 (5) ◽

pp. 765-774

Author(s):

Pearay L. Ogra

Keyword(s):

Immune System ◽

Lymphoid Tissue ◽

Mammalian Species ◽

Complex Molecule ◽

Secretory Component ◽

Secretory Iga ◽

Cell Mediated Immunity ◽

Immune Reactivity ◽

Upper Respiratory Tract ◽

Local Immunity

The classic studies of Tomasi and his colleagues' in early 1960s demonstrated that the predominant class of immunoglobulin in various external fluids was of IgA class, although it is a relatively minor immunoglobulin in serum. These observations represent the foundations of the earlier concept of the secretory immune system. Subsequent studies conducted during the last decade have made it clear that in addition to IgA, other immunoglobulin (IgM, IgE, IgG), components of T-cell-mediated immunity and other nonimmunologic factors are also present in significant amounts in the external mucosal secretions.2,3 Thus, the current concept of the local (secretory) immune system includes the secretory IgA, other immunoglobulins and cell-mediated immune reactivity. The local immune system is referred to the complex mechanisms of specific immunity existing on the external mucosal surfaces and which appear to operate somewhat independent of the immune function in other systemic sites in man and most other mammalian species. The local immune system includes the bronchus associated lymphoid tissue (BALT), gut associated lymphoid tissue (GALT), and the immunocompetent cell or organized lymphoid follicles in the conjunctiva, salivary glands, and upper respiratory tract, genitourinary tract and mammary glands.4-6 A number of publications3,4 have extensively reviewed the development and function of the secretory immune system. In this report, an attempt will be made to provide an overview of the more recent developments in the mechanisms of local immunity. SECRETORY IMMUNOGLOBULINS Structure of Secretory IgA The bulk of the IgA immunoglobulin in external secretions exist as a complex molecule which consist of three immunologically distinct components: (1) a dimer of two 7 S IgA molecules, (2) the J (joining) chain, and (3) the secretory component (SC).

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Effects of formaldehyde and xylene on CD4- and CD8-positive T cells in bronchus-associated lymphoid tissue in rats

Toxicology and Industrial Health ◽

10.1177/0748233708089025 ◽

2007 ◽

Vol 23 (8) ◽

pp. 471-477 ◽

Cited By ~ 7

Author(s):

M Sandikci ◽

U Eren ◽

S Kum

Keyword(s):

T Cells ◽

T Lymphocytes ◽

Lymphoid Tissue ◽

Exposure Period ◽

Sprague Dawley ◽

Adult Rats ◽

Local Immunity ◽

Two Agents ◽

Sprague Dawley Rats

The aim of this study was to determine the localization and number of CD4- and CD8-positive T lymphocytes in bronchus-associated lymphoid tissue (BALT) of the embryos and newborns or young and adult rats exposed to formaldehyde (6 ppm), technical xylene (300 ppm), or a combination of these two agents (3 ppm + 150 ppm) for 6 weeks (8 h/day). A total of 96 female Sprague-Dawley rats were used. The CD4-positive cells were localized predominately in area under the epithelium and in the periphery of BALT follicles after the exposure period. However, CD8-positive cells were localized mainly in the periphery of BALT follicles after the exposure period. The number of CD4- and CD8-positive lymphocytes significantly increased in exposed young and adult rats compared to the respective controls. These results suggest that formaldehyde and/or xylene may affect the local immunity in BALT particularly in young and adult rats.

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