Mucosal immune system (MALT) MALT (Mucous Associated Lymphoid Tissue) •GALT (Gut Associated Lymphod tissue) •BALT (Bronchi Associated Lymphoid Tissue) •Immune stissues of the urinary tract, genital tract, conjunctiva, middle ear… •Includes also brest gland! Anatomy of MALT •Diffuse tissue containing lymphocytes and other cells of the immune system in submucosa. •Specialized organs: –Waldeyer´s ring –Payer´s patches –Appnedix Mucosal immune system (MALT) •Antigenic stimulation in one part of MALT leads to immune response also in other compartments of MALT. •IgA is a predominant immunoglobulin secreted through the epitelial cells. •Oral administration of antigens frequently leads to induction of immune tolerance. •Intraepitelial lymphocytes - CD8+, restricted antigenic specificity. TL-str Common Immune System of Mucous Membranes TL-zena1 Common immune system of mucous membranes Homing of Lymphocytes •The directed migration of subsets of circulating lymphocytes into particular tissue sites. •Regulated by selective expression of adhesion molecules called homing receptors on lymphocytes. •Tissue speciphic endothelial ligands are called addressins. High endotelial venules •Specialized venules. The site where lymphpocytes leave the blood stream and migrate into lymph nodes, spleen, organs of MALT. •Adhesion molecules enable selective attachment of various types of lymphocytes. S0241X-001-f017 Downloaded from: StudentConsult (on 15 July 2006 09:09 AM) © 2005 Elsevier top_logo Circulation of lymphocytes S0241X-008-f009 Downloaded from: StudentConsult (on 20 July 2006 11:29 AM) © 2005 Elsevier top_logo Intraepitelial T-lymphocytes •TCR ab or gd •Extrathymic differentiation •First line of specific immune response •Predominantly CD8+ •Low antigenic specificity of TCR M-cells •Specialized enterocytes responsible for transport of antigens from the gut towards the immunocompetent cells inside the Payer´s patches. •Transport in mediated by transcytosis. Lymphocyte circulation in GALT 267_mehandru_saurabh_fig1_680 www.prn.org/.../hiv_1_gastrointestinal_galt_267 Oral tolerance •Stimulation of the GALT frequently leads to induction of immune tolerance to the stimulating antigen. •This occurs mainly if the gut is in „normal, non-inflammatory“ conditions. •Induction of Th3 cell is the main mechanism. •The tolerance is important to avoid unnecessary reactions to non-pathogenic antigens.