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Neutrophils, Monocytes, Macrophages, Dendritic and Mast Cells |
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Main defensive job is against parasites Increased numbers in the blood are indicators of allergy Have surface receptors for antibodies (IgE) responsible for immediate hypersensitivity (allergies such as hay fever) When IgE antibodies react with surface receptors, degranulation occurs Degranulation contributes to the manifestations of immediate hypersensitivity diseases such as hay fever |
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Neutrophils, Granulocytic neutrophils, Polymorphonuclear neutrophils (PMNs) |
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Are the first cells to arrive at inflammation Are phagocytes
Have a lobed nucleus and granulocytes |
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Have surface receptors for antibodies (IgE) responsible for immediate hypersensitivity (allergies such as hay fever) When IgE antibodies react with surface receptors, degranulation occurs Degranulation contributes to the manifestations of immediate hypersensitivity diseases such as hay fever |
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Monocytes and Macrophages |
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Are phagocytes Monocytes circulate in the blood, and when they enter tissue, mature into macrophages Monocytes arrive at inflammation after PMNs Are effectors in both innate and adaptive immunity Recruit other cells to inflammation Present antigens to T cells for the cellular immune response Have surface receptors for antibodies that are attached to pathogens enhancing phagocytosis |
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Large macrophages found in most soft tissue Especially found in lymph nodes and spleen Are especially important as APCs to T cells |
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In the bone marrow, B cell development of specific antigen receptors is antigen independent and due to DNA rearrangement Immature B cells, developing in the bone marrow, undergo apoptosis upon recognition of self antigens B cell activation into antibody producing, then antibody secreting plasma cells is antigen dependent Each B cell can have thousands of receptors on its surface that are specific for the same antigen
Depending on the type of antigen presented to the B cell, B cells can proliferate by themselves or they need to interact with T cells to proliferate B cells that interact with T cells gain the ability to switch from IgM, the first antibody produced to IgG or other antibody classes (isotypes) B cells that react with T cells also develop into antibody secreting plasma cells or B memory cells that live for years. |
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Immature T cells home to the thymus and are called thymocytes while they mature T cells develop their antigen specific receptors in the thymus independent of antigenic stimulation via DNA rearrangement T cells are selected for maturation only if their T cell receptors (TCRs) do not react with self T cells are important in regulating the adaptive immune response, are responsible for cell mediated immunity and help certain B cells to produce antibody and mature into plasma cells |
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Clusters of Differentiation(CDs) |
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In immunology, CDs refer to surface molecules on leukocytes with specific functions. CDs are often used as identifying markers for a subpopulation of cells These markers are proteins that have specific functions Immunologists often refer to cells by their CD designation, ex. that batch of cells are CD4 positive or those are CD4 cells |
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Express CD4 and are often called CD4 cells Regulate antigen-directed effector functions in cell mediated immunity Stimulate B cells to proliferate , undergo isotype switching and differentiate into antibody producing cells Recognize antigen complexed with MHC class II molecules on dendritic cells, macrophages , monocytes and B cells |
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Cytotoxic T Lymphocytes (CTLs) |
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Express CD8 and are often called CD8 cells Are cytotoxic to host cells infected with intracellular pathogens (viruses) and to tumor cells Are cytotoxic in an antigen specific manner dependent upon the expression of MHC I molecules that are expressed on all nucleated cells in the body |
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The liver in the fetus and bone marrow in adults is the site of the origin of leukocytes Because of recirculation, the bone marrow also functions as a secondary lymphoid organ
The thymus reaches maturity prior to puberty and then slowly loses function The thymus is situated in the anterior mediastinum The primary function of the thymus is to educate T cells to differentiate between self antigens and non-self antigens The thymus is the site of T cell maturation |
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Secondary Lymphoid Organs |
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The secondary lymphoid organs are the major areas where lymphocytes come in contact with antigens Lymph nodes and spleen are the most important secondary organs Next of importance are the MALTS or mucosa associated lymphoid tissues found lining the digestive and respiratory tracts |
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The spleen is located in the left upper quadrant of the abdomen The spleen acts as a filter in the blood and is the major site of immune responses to antigens in the blood It contains areas for T and B cells APCs are found in areas called germinal centers and present antigens to the lymphocytes in these areas |
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The lymphatics are a network of thin tubes that drain interstitial fluid from the body and eventually return it to the circulatory system There are many lymph nodes in the body where filtration of the lymph takes place. APCs reside in the nodes, collect antigens brought to the nodes from the tissues and present them to the T and B cells |
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Aggregates of lymphoid tissue that reside along the respiratory and digestive tracts comprise the MALTS In general, they play the same kind of role as lymph nodes, but are active in delivering antigens in the respiratory and digestive tracts to the lymphocytes |
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most abundant isotype and is the longest lasting |
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mediates immediate hypersensitivity (allergy) and reacts with parasites |
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the largest isotype molecule and is the strongest activator of complement; we’ll cover complement later. We mentioned complement earlier as an innate immune component. IgM is also the first antibody produced in response to antigen, and was the first antibody produced in the phylogenetic tree |
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found on the surfaces of epithelial cells and in the secretions of the respiratory and digestive system. It is the main immunoglobulin in secretions such as saliva, tears, and milk |
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consists of 2 molecules of IgA, a joining chain (J) and a secretory component. The secretory component protects the molecule from proteolytic attack and facilitates its transfer across epithelial cells into secretions. |
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strong binder of complement and while all four subclasses cross the placenta to provide antibodies to the fetus from the mother |
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has the least placental passage |
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Antibody valency is the number of binding sites on an antibody molecule. IgG is bivalent or has a valency of 2. What is the valency of IgM? Affinity is the strength of a single binding site between antibody and antigen. Avidity is the overall strength of interaction between the 2 molecules and depends on the affinity of each binding site multiplied by the valency. We can easily see that IgM with 10 binding sites might have great avidity if the affinity of each binding site is fairly good. |
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