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75 Cards in this Set
- Front
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IFN-alpha, IFN-beta
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made by cells in response to viruses
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IFN-gamma
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Much less antiviral activity
made in response to immune stimuli; produced by T cells and NK cells; activate APCs partly by inducing MHC II molecules and they in turn can activate T cells by secreting IL-1 and IL-6 (positive feedback) |
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IL-1
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Made by macrophages (and B cells and endothelial cells);
Stimulates T and B cells and induces inflammatory responses; Induces fever; Virtually all cells in body have IL-1 receptors |
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IL-2
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Produced by T cells and LGLs (NK cells);
Most powerful activator and growth factor; Acts on LGLs and B cells to induce growth and differentiation |
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IL-3
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Stimulates growth of precursors of all hematopoetic lineages (RBCs, granulocytes, macrophages, lymphocytes)
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IL-4
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Acts on B cells to induce activation and differentiation;
Acts on T cell to promote differentiation of TH2 cells |
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IL-6
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Produced by T cells, macrophages, B cells, fibroblasts, and endothelial cells;
Acts on B cells to differentiate into antibody-forming cells (AFCs) |
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Lymphoid lineage
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Produces lymphocytes (B cells, T cells, NK cells)
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Myeloid lineage
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Produces phagocytes (monocytes, macrophages and neutrophils) and other cells.
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Where do T cells develop?
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Thymus
(primary lymphoid organ) |
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Where do B cells develop?
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fetal liver and adult bone marrow
(primary lymphoid organs) |
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Resting T cells
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majority are small, non-granular with a high N:C ratio
Carry a "Gall body"-consists of a cluster of lysosomes associated with a lipid droplet about 10% of TH and 35% of Tc cells diplay LGL morphology with primary lysosomes dispersed in the cytoplasm and a well developed golgi apparatus |
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Resting B cells
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do not display Gall bodies or LGL morphology,
cytoplasm scattered with ribosomes activated B cells have developing rough endoplasmic reticulum (RER) plasma cells are cell blasts that are producing antibody |
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NK cells
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Have no antigenic receptors on their surface;
Characterized by LGL morphology |
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CD (cluster designation) system
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a system of nomenclature,
CD refers to clusters of antibodies that recognize a particular cell marker. |
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What are the types of T cell antigen receptors (TCRs)?
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Two types:
TCR-1 ~ a heterodimer of two disulfide-linked polypepitdes gamma and delta (5-10% of T cells) TCR-2 ~ a heterodimer of two disulfide-linked polypepitdes alpha and beta(90-95% of T cells) |
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CD3 complex
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Both receptors TCR-1 and TCR-2 are associated with a set of five polypeptides, collectively known as the CD3 complex, to give the T-cell receptor complex (TCR-CD3)
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What marker is on the surface of a TCR-2 TH cell?
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CD4
Helps or induces immune response |
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What marker is on the surface of a TCR-2 TC cell?
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CD8
Predominantly cytotoxic functions |
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What class of MHC can a CD4 cell recognize?
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MHC class II
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What MHC class can a CD8 cell recognize?
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MHC class I
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What cytokines do TH1 cells secrete?
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IL-2 and IFN-gamma
Important in combating viruses, bacteria and parasites In response to intracellular pathogens |
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What cytokines do TH2 cells secrete?
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IL-4, IL-5, IL-6, and IL-10
stimulate B cells to proliferate and produce antibodies In response to extracellular pathogens |
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What constitures the B cell receptor complex (BCR)?
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B cells in peripheral blood express two immunoglobulin isotypes on their surface, IgM and IgD
the surface IgM is associated with other molecules on the B cell surface to form the 'B cell antigen receptor complex' (BCR) |
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B cell markers
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Majority of B cells have MHC class II antigens on their surface (important for B and T cell interactions)
CD19, CD20 and CD22 are the main markers used to identify human B cells |
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Natural Killer cell markers and function
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express neither TCR nor BCR antigen receptors
NK cell function is to recognize and kill certain tumor cells and virus-infected cells |
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Activation of T cell
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T cells 'see' the antigen in association with an MHC molecule on antigen-presenting cells
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Activation of B cell
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B cells can bind free antigen but generally need help from the T cells to become activated
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Activated B cell
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Antibody forming cells;
Following B cell activation, the B cell matures into an antibody -forming cell (AFC) and eventually to terminally differentiated plasma cells. short-lived, surviving only a few days activated B cell expresses new surface markers upon activation, such as MHC class II markers, IL-2R, as well as, IL-3, IL-4, IL-5 and IL-6 receptors |
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Monocyte characteristics
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large in comparison to lymphocytes
has a horse-shoe shaped nucleus, often contains azurophilic granules they contain peroxidase and several acid hydrolases (important for intracellular killing) |
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Macrophage/Monocyte cell markers
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Fc receptors for IgG -trigger extracellular killing, opsonization (complement binds to immune complexes), and phagocytosis
Complement receptors Class II MHC molecules Receptors for cytokines, IL-2, IL-4 and IFN-gamma their functions can be enhanced by T cells through these receptors |
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Antigen Presenting Cells
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heterogeneous population of leucocytes
cells other than leucocytes, such as endothelial or epithelial cells can also acquire the ability to present antigens when stimulated by cytokines found primarily in the skin, lymph nodes, spleen and thymus mechanism of carrying antigens from the skin to the T cells in the lymph nodes are rich in class II MHC molecules; important for presenting antigen to T cells B cells are also considered APCs |
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Langerhans cells
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archetypical APC
located in the skin travel as 'veiled cells' into the lymph nodes |
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Follicular dendritic cells
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Antigen presenting cell
found in the B cell areas of the lymph nodes and spleen. they present antigen to B cells and lack class II MHC molecules express high levels of FcR and complement receptors for interaction with immune complexes. |
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Interdigitating cells
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Antigen presenting cells
Located in thymus play a role in deleting T cells that react against self antigens |
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Granulocytes and Mast cells
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polymorphs are referred to as granulocytes or PMNs
produced in bone marrow; short-lived (2-3 days) compared to monocytes and macrophages PMNs can adhere to endothelial cells lining blood vessels and squeeze through the cells to enter the tissue (diapedesis) show no specificity for antigens but synergize with antibodies and complement in protection against microorganisms |
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Diapedesis
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PMNs can adhere to endothelial cells lining blood vessels and squeeze through the cells to enter the tissue
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Neutrophils
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90% of granulocytes;
multi-lobed nucleus The primary granules are lysosomes containing acid hydrolases, myeloperoxidase and muramidase The secondary granules contain lysozyme the ingested organisms are contained within vacuoles termed phagosomes, which fuse with lysosomes to form phagolysosomes |
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Eosinophils
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Bi-lobed nucleus and many cytoplasmic granules
ability to phagocytose and kill ingested microorganisms Usually degranulates instead play a specialized role in immunity to parasitic worms using this mechanism |
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Degranulization
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involves fusion of the intracellular granules with the plasma membrane and release of the granule contents into the surrounding area;
this is the way that large targets are phagocytosed |
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Basophils
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are found in circulating blood;
characterized by deep blue-violet granules |
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Mast cells
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are not found at all in circulation and are indistinguishable from the basophil in its properties
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Basophil and Mast Cell actions
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the stimulus for basophil and mast cells degranulation is often an allergen
the allergen must cross link with IgE that is bound to the basophil and mast cell via Fc receptors for IgE all granules are released; histamine is released by degranulation giving the adverse symptoms of allergy. they play a role against parasites |
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Allergen
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an antigen that causes an allergic reaction
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Platelets
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involved in the immune response and especially in inflammation
following injury to endothelial cells, they adhere to surface of the damaged tissue the platelets release substances that increase permeability, in addition to factors that activate complement |
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Primary Lymphoid organs
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Thymus - T cells
Fetal liver, adult bone marrow - B cells |
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Thymus
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bilobed organ located in the thoracic cavity
each lobe is organized into lobules separated by connective tissue trabeculae within each lobule the lymphoid cells are arranged into an outer cortex and an inner medulla in thymic lobules, are also present interdigitating cells (IDCs) and mactrophages the thymus involutes with age; atrophy begins at puberty and continues throughout life |
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Outer cortex of Thymus
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contains relatively immature proliferating thymocytes
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Medulla of Thymus
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contains more mature cells, suggesting a differentiation gradient from the cortex to
medulla Hassals' corpuscles are found in the thymic medulla, its function is unknown (contains degenerating epithelial cells) |
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High Endothelial Venules (HEVs)
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traffic of cells into and out of the thymus occurs through these
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Hassals' corpuscles
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found in the thymic medulla,
its function is unknown (contains degenerating epithelial cells) |
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Bursa of Fabricius
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modified section of the intestinal and genitourinary tracts of birds
organized in cortex and medulla |
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Fetal liver and Bone marrow
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islands of hemapoetic cells in the fetal liver and in the fetal and adult bone marrow give rise to B lymphocytes
adult bone marrow contains mature T cells, thus, making the bone marrow an important secondary lymphoid organ (provides an environment for interactions between B and T cells) |
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Secondary Lymphoid Organs
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Spleen
Lymph Nodes Mucosal-associated lymphoid tissues (MALT) |
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Spleen
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is responsive to blood-borne antigens
it has two main types of tissue: white pulp and red pulp |
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White pulp (of spleen)
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consists of lymphoid tissue that surrounds a central arteriole and it is called periarteriolear lymphoid sheath (PALS)
T cells surround arteriole B cells are arranged into primary "unstimulated" follicles and secondary "stimulated" follicles (posess a germinal center with memory cells) the germinal centers contain follicular dendritic cells and phagocytic cells macrophages and B cells are found in the marginal zone-area that overlying the secondary follicles |
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Red pulp (of spleen)
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consists of sinuses containing macrophages, erythrocytes, platelets, granulocytes and plasma cells
site where aged erythrocytes and platelets are destroyed capillaries that ended at the PALS extend and open freely to the red pulp cords. Thus, circulating cells enter and become trapped at the cords where they can be phagocytosed |
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Lymph nodes
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form a network that filters fluid derived from blood in the tissue spaces
frequently found at branches of the lymphatic vessels strategically placed in areas of the neck, groin, and abdominal cavity which drain superficial and deep regions of the body lymph nodes are 2-10mm in diameter, are round or kidney shaped fluids enter through several afferent lymphatic vessels and leaves the node through one efferent lymphatic vessel at the hilus |
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Cortex of Lymph Node
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contains aggregates of B cells as primary or secondary follicles
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Paracortex of Lymph Node
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T-cell area
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Central Medulla of Lymph Node
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consists of T cells, B cells, plasma cells and macrophages
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Mucosal Associated Lymphoid Tissue(MALT)
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aggregates of non-encapsulated lymphoid tissue are found in the lamina propria and submucosal areas of the gastrointestinal, respiratory and genitourinary tracts
lymphoid cells are present in aggregates containing germinal antibody IgA is the most common antibody present at mucosal surfaces it transverses mucosal membranes and helps prevent entry of infectious microorganisms |
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Action of IgA
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plasma cells secrete IgA into the intestinal space
IgA binds to a receptor on the internal surface of the epithelial cells is then endocytosed and transported across the cell IgA is released to the luminal surface (outside) of the cell where it can protect the mucosal surface from antigens |
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Lymphocyte Traffic
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the main exit route of lymphocytes from blood is through the high endothelial venule (HEV)
in the lymph nodes, HEVs are primarily found in the paracortex and some in the cortex Lymphocyte trafficking exposes antigen to a large number of lymphocytes Lymphocytes within lymph nodes return to blood circulation by efferent lymphatic vessels, which pass through the thoracic duct into the left subclavian vein |
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What happens to Lymphocyte traffic when antigen is encountered?
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when antigen enters the lymph nodes all traffick shuts down for 24 hours, so that antigen-specific lymphocytes are retained in the lymph node where antigen is drained
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Adaptive Immune Response
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2 molecules involved:
1) immunoglobulins 2) T cell antigen receptors |
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Immunoglobulins
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group of glycoproteins present in the serum and tissue fluids
some are carried on the surface of B cells where they act as receptors some (Ab) are free in blood and lymph the membrane bound Ig has the same antigen binding specificity as does the antibody produced by the plasma cell. |
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Five classes of Immunoglobulins
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IgG, IgA, IgM, IgD, and IgE
differ in size, charge, amino acid composition and carbohydrate content |
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Why are Immunoglobulins bi-functional molecules?
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One region binds to antigen while a different region mediates effector functions
effector functions include binding of the Ig to host tissues, binding to cells of the immune system, and to the first component (C1q) of the complement system |
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Structure of Immunoglobulins
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The basic structure of all immunoglobulin molecules is a unit consisting of two identical light polypeptide chains and two identical heavy polypeptide chains
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IgG
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major immunoglobulin in normal human serum
It consists of a single four-chain molecule Maternal IgG confers immunity to neonates- it crosses the placenta giving passive immunity to the newborn |
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IgM
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it is a pentamer of the basic four-chain structure
it is confined in the intravascular pool It is predominantly the "early " antibody,- it is the first immunoglobulin class produced in a primary response to antigen because of steric hindrance it can only bind to 5 molecules of antigen even though it has 10 binding areas |
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IgD
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less than 1% of the total plasma Ig
present in large quantities on the membrane of many B cells function is unknown |
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IgE
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scarce in serum, found on surface membrane of basophils and mast cells
plays role in immunity against parasitic helminths associated with allergic diseases such as asthma and hay fever |
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IgA
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found in external secretions, such as breast milk, saliva, tears, mucosal surfaces
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