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What is the main function of Regulatory T cells? INNATE IMMUNITY includes what?
- Physical Barriers
- Cellular Barriers
- Chemical Barriers
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What are the Features of Innate Immunity?
- First Line of Defense
- Present on Birth
- Non-specific
- Resistance not improved by repeated infections
- Physiological Barriers
- Phagocytosis, Inflammation, Fever
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What are the characteristics of the Adaptive/Acquired Immunity?
- Resistance improves after repeated infections
- Cells involved include B lymphocytes, T lymphocytes and Macrophages
- Primary and secondary lymphoid organs are involved in the process
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What is an IMMUNOGEN?
Any agent inducing an immune response
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What are the characteristics of an immunogen?
- Foreignness
- High Molecular Weight
- Chemical Complexity
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What is an Antigen?
Any agent capable of binding specifically to components of immune response
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What are the antigens composed of?
- Carbohydrates
- Lipids
- Nucleic Acids
- Proteins
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What are Antibodies?
Soluble globulin proteins
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What are the characteristics of antibodies?
- Specificity
- Distinct biological activity
- Four chain structure: two identical light and two identical heavy chains
- Three fragments of equal sizes
- Fab fragment
- Fc fragment
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What are the Functions of IgG?
- Agglutination , precipitation and opsonisation
- Conferral of immunity to fetus
- ADCC
- Activation of complement
- Neutralization of toxins and viruses
- Immobilization of bacteria
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What are the Properties of IgM?
- Pentamer molecule
- Synthesized after immunization
- Elevated levels levels indicate recent infection
- Synthesized by placenta and elevated levels in fetus indicative of congenital infection
- Best agglutinating and complement-activating antibody
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What are the properties/functions of IgA?
- Major immunoglobulin in secretions
- Monomeric as well as Diameric
- Role in Mucosal infections
- Bactericidal Activity
- Antiviral Activity
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What are the properties/functions of IgD?
- Causes the differentiation of B cells to a more mature form
- Present on the surface of B lymphocytes
- Present in monomeric form
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What are the properties/functions of IgE?
- Reaginic antibody
- Protects against parasites
- Important role in hypersensitivity
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How do Primary and Secondary Antibody Responses differ?
- Time course; secondary response has a shorter lag phase and an extended plateau and decline
- Antibody titer: greater in secondary response
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What are the LYMPHOID CELLS?
- T cells: develop in the thymus
- B cells: differentiate in fetal liver and adult bone marrow
- NK cells: does not possess T cell or B cell receptors
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What are the characteristics of T Cells?
- The definitive T cell marker is the cell antigen receptor (TCR)
- TCR-1 (Composed of ϒ and Ϭ chains, 5%)
- TCR-2 (Composed of α and β chains, 95%)
- Both receptors are associated with a complex of polypeptides making up the CD3 complex.
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The TCR-2 cells are divided into two major subsets, what are they?
- CD4+ (Helper T cells)
- CD8+ (Cytotoxic T cells)
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CD4+ (Helper T cells) TCR-2 cells are divided into what subgroups?
- CDw29+ (positively influence the immune response of T cells and B cells-the helper function)
- CD45R+ (Induce cytotoxic function in CD8+ cells)
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Their principal functions include a negative feedback after the generation of an immune response and to protect from autoimmunity.
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CD4+ T cells mediate ________________independent of CD8+ T cells.
suppressor function
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____________ maintain self tolerance and suppress responses to foreign antigens.
Regulatory T-cells
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______________T cells are mature T cells with a distinct regulatory function.
CD4+CD25+
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What are the main Regulatory T cells?
- CD4+ CD25+ T cells,
- peripheral Treg cells,
- IL-10 secreting Tr1 cells
- TGFβ secreting TH3 cells,
- CD8+CD28- T cells, CD8+CD122+ T cells, Qa-1-restricted CD8+ T cells,
- γ/δ T cells
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What are the features of Memory T cells?
- Memory T cells persist even after the invading pathogen has been eliminated.
- There are two types of memory T cells, central memory T cells and effector memory T cells.
- They are either CD4+ or CD8+ and respond quickly after they see the antigen at a second time.
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What are the features of NKT cells?
- They perform cytotoxicity and mostly are not MHC-restricted.
- They recognize antigens which are glycolipids and require CD1d.
- They release cytokines including IL-4, IFN-γ, GM-CSF. and others.
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What are the features of NKT cells?
- NKT cells bridge innate and acquired immune responses.
- Abnormal NKT cell function may be associated with cancer and autoimmune disease.
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What are the features of B lymphocytes?
- These lymphocytes are unique due to their ability to secrete immunoglobulins (Defined by the presence of immunoglobulins)
- B cells are produced in the bone marrow.
- The development of B cells occur at various stages
- Express both IgM and IgD molecules
- Expression of IgG, IgA and IgE on the cell surface is not common in circulation
- Majority of B cells carry MHC class II antigens
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What are the features of Natural Killer cells?
- NK cells are the third largest class of lymphocytes.
- They develop in bone marrow from common lymphoid progenitor.
- NK cells share effector function and the ability to produce cytokines with T cells. They do not express either T cell or B cell receptors.
- Large granular lymphocytes.
- NK cells participate in innate immunity and are the first responders against infection and possibly tumors.
- They carry CD56 antigen
- The killing ability of NK cells is associated with the expression of MHC Class I molecules.
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What are the Antigen Presenting cells?
- Macrophages
- B cells
- Dendritic cells
- Langerhan cells
- Interdigitating cells
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What are the features of Macrophages?
- Macrophages participate in innate as well as acquired immune response.
- They are phagocytes which continuously remove self proteins which are degraded and presented to T cells
- The most important role of macrophages is antigen presentation.
- They also play a role in inflammatory responses, anti-tumor activity, microbicidal activity, lymphocyte activation and tissue reorganization.
- Most of their effects are mediated via cytokines.
- They release oxygen dependent free radicals, collagenases, and angiogenesis factors.
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What are the features of Dendritic Cells?
- Dendritic cells are antigen presenting cells.
- They are distributed in small quantities in various tissues including skins, inner lining of the nose, lungs, stomach and intestine.
- The blood contains immature dendritic cells.
- After activation, dendritic cells migrate to the lymphoid tissue to initiate an acquired response after interacting with B and T cells.
- There are two most common types of dendritic cells, myeloid dendritic cells and lymphoid dendritic cells.
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What are the features of Myeloid dendritic cells?
- Secrete IL-12 and are very similar to monocytes
- mDC can be divided into at least two subsets, mDC1 and mDC2.
- mDC1 stimulates T cells, whereas mDC2 may have a role in fighting wound infection.
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What are the features of Lymphoid dendritic cells?
- Similar to plasma cells and produce high levels of interferon-ϒ.
- The dendritic cells are of hematopoietic origin.
- The myeloid dendritic cells are of myeloid origin and lymphoid dendritic cells are of lymphoid origin.
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What are the features of Neutrophils/Polymorphonuclear leukocytes?
- They are produced in the bone marrow.
- Neutrophils are phagocytes.
- They utilize a number of bactericidal substances, lytic enzymes, and both oxygen-dependent and oxygen-independent pathways to kill microbes.
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What are the features of Eosinophils/Polymorphonuclear leukocytes?
- Eosinophils develop in bone marrow, where they also mature.
- Eosinophils are also capable of phagocytosis.
- They are involved in combating parasitic infection and play a role in allergic disease.
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What are the features of Basophils and Mast cells?
- Basophils are of bone marrow origin.
- They secrete a number of mediators including histamine, leukotrienes, and several cytokines.
- Mast cells are similar to basophils, but they have different precursor cells in the bone marrow. The precursor cells for both basophils and mast cells express CD34.
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