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
EXPRESION
• enzymes
• HLA antigens
• adhesion molecules
• receptorsyfor:
mikrobes
cytokines
polymeric Ig
PRODUCTION
• cytokines
pro-inflammatory
growth factors
chemotactic
• antibiotic peptides
• various other mediators
INTERACTION WITH SPECIFIC IMMUNE SYSTEM
Epitelial cells are intergal part of the immune
system of mucous membranes
Antimicrobial nechanisms on mucous
membranes
Factor Mechanismus
Comensal bacteria competition with pathogens
production of antiinflammatory mediators
Tight epitelial junctions protect from bacterial invasion into tissues
Cilia bind and remove microbes
Mucin bind microbes
Lysozyme killing G+ bacteria
Laktoferin iron binding (inhibition o microbial growth)
Antibiotic peptides killing microbes
(mainly b defensins)
Secretory Ig Microbial adhesion blocade
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.
Comensal (normal) mikroflóra
(of GIT)
• ~ 1014 microbial cells, ~ 1000 microbial species
• ~ 50% non cultivated
• Complex ecosystem
• Included in innate immunity of GIT
• Mutual interactions of microorganisms:
competition, symbiosis..
• Interaction with macroorganism: symbiosis,
commensalism, important in metabolic processes
(production of vitamins etc.)
• Immune system modulation