LT 2: Introduction to the immune system
Mechanisms of disease 1 (301217010Y)
Universiteit Leiden
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LT 2: Introduction to the immune system The basic defense mechanisms of the body is organized in 3 layers 1. Physical & chemical barriers a. All the surface areas: skin, but also the tracts: respiratory, urogenital, gastrointestinal b. Bacteria in intestine: commensal flora c. Epithelia form a tough impenetrable barrier which lines the outer surface and inner cavities of the body i. Cilia: wipe out mucus ii. Mucus: contains anti-microbial agents - If the barrier is broken instant response trying to get rid of the pathogens - The first physical barrier = epithelial cells joined by tight junctions & cilia 2. Innate immune system a. Microenvironment is putting out signals, that something may go wrong - Neutrophils are the most common leukocytes in the blood, followed by the lymphocytes then monocytes - Purple square: leukocytes/ white blood cells - Blue square: innate immune cells - Yellow square: adaptive immune cells o Restricted to the lymphoid lineage - - I n n a t e immune system is a primitive immune defense Innate and adaptive immunity have a common goal: the destruction of pathogens Recognition mechanisms of innate immunity Rapid response (hours) Fixed set receptors Limited number of specificities Constant during response Recognition mechanisms of adaptive immunity Slow response (days to weeks) Variable set of receptors Numerous highly selective specificities Improve during response When lacking innate immunity: microorganisms increase rapidly and you die 3. Adaptive immune system - T + B cells are mostly found in the secondary lymphoid organs o Lymph nodes are connected and end in the ductus thoracicus - And in the primary lymphoid organs: where the cells are produced o Bone marrow o Thymus: final maturation and education of T lymphocytes - Unlike mature B cells, precursor T cells arise in the bone marrow, but require additional maturation in the thymus. After that, they leave the thymus and travel to secondary lymphoid tissues. - Most of the secondary lymphoid tissue is localized in the gastro- intestinal tract o GALT: tonsils, Peyer’s patches, mesenteric, appendix, adenoids o BALT: brochial o MALT: mucosa-associated - T & B cells live in different compartments inside of the lymph node. - - - Spleen is filtering the blood o White pulp macrophages have the same function as the macrophages that lines the marginal sinus in the lymph node filter the blood, get the pathogens from the blood and present these to the Bcells Langerhans cells (innate) antigen presenting cells / dendritic cells o Lie in epidermis or at the junction of epidermis and dermis o Sentinel cells (schildwacht) o In skin and mucosa T & B cells are constantly on the move highest likelihood of encountering the antigen o Small proportion of lymphocytes in the blood, because it’s travelling o Most of it is hidden in tissues (from most to less): Lymph nodes Extra-lymphoid organs Spleen Bone marrow (produces new lymphocytes and is the home of memory cells
LT 2: Introduction to the immune system
Vak: Mechanisms of disease 1 (301217010Y)
Universiteit: Universiteit Leiden
