Mucosal immune system
(MALT)
MALT (Mucous Associated
Lymphoid Tissue)
• GALT (Gut Associated Lymphod tissue)
• BALT (Bronchi Associated Lymphoid
Tissue)
• Immune tissues 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 by the epitelial cells.
• Oral administration of antigens frequently
leads to induction of immune tolerance.
• Intraepitelial lymphocytes - CD8+,
restricted antigenic specificity.
Mucous- asccociated lymphoid tissue
Nasopharynx
Lungs
Mammary gland
Gastrointestinal tract
Genitourinary tract
Vena cava
Ductus
thoracicus
Intestine
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.
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© 2005 Elsevier
Circulation of lymphocytes
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© 2005 Elsevier
Secretory IgA formation
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
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, noninflammatory“
conditions.
• Induction of Th3 cell is the main mechanism.
• The tolerance is important to avoid unnecessary
reactions to non-pathogenic antigens.