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71 Cards in this Set
- Front
- Back
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What triggers specific immune responses in the body?
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-antigens
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What forms can antigens take?
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-bacterial cell walls
-capsules -pili -flagella -viruses -fungi -protozoa |
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How do antigens enter the body?
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-breaks in the skin (and mucous membranes)
-direct injection (as with a bite or needle) -organ transplants (and skin grafts) |
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What does the lymphatic system do?
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-to screen the tissues of the body for foriegn antigens
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What do lymphatic vessels do?
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-form a one-way system that conducts lymph from local tissues and returns it to the circulatory system
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What is lymph?
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-liquid with similar composition to blood plasma that arises from fluid leaked from blood vessels into surrounding tissues
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Where do lymphoid cells develop?
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-stem cells
-red bone marrow |
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What designates B and T lymphocytes?
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-glycoprotein found on surface
ie: CD4, CD8 |
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Where do B cells mature?
T cells? |
B=bone marrow
T=thymus |
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Where are B-cells found?
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-spleen, lymph nodes, red bone marrow, and Peyer's Patches
*small percentage circulating in blood |
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What is the major function of B cells?
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-secrete antibodies such as immunoglobulins
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What is the humoral immune response?
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-body fluid immunity (such as lymph and blood)
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What are antigen-binding sites?
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-complementary to antigenic determinants (epitopes)
-form strong, noncovalent interactions -Hydrogen bonds and other attractions may also be involved |
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What are 6 antibody functions?
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-activation of complement
-stimulation of inflammation -agglutination -neutralization -opsonization -antibody-dependent cell mediated cytotoxicity |
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What is agglutination?
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-each antibody has 2 antigen binding sites
-binding of multiple antibodies can lead to clumping or agglutination |
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What is neutralization?
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-binding to toxin or cell, thereby blocking active sites or adherence to target cells
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What is opsonization?
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-AKA enhanced phagocytosis
-phagocytes have receptors that recognize parts of antibodies -coating of antigen with antibodies |
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What is antibody-dependent cell mediated cytotoxicity?
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-attachment of antibody to target cell leads to lysis by non-specific immune cell
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What does antibody classification depend on?
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-type of foreign antigen
-portal of entry -antibody function needed |
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What are 5 antibodies?
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-IgG
-IgM -IgA -IgE -IgD |
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What is the function of IgG?
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-complement activation, agglutination, opsonization, and neurtralization
-crosses placenta to protect fetus -85% in serum |
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What is IgM?
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-complement activation, agglutination, and neutralization
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What is IgA?
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-Agglutination and neutralization
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What is IgE?
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-Triggers release of histamines from basophil mast cells
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What is IgD?
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-unknown
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What antibody is the only non-monomer (pentamer)?
How about a dimer? |
-IgM
-IgA (also a monomer) |
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What is a B-cell receptor (BCR)?
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-antibody molecule that remains attached to cytoplasmic membrane of B cells
-complementary to only one antigenic determinant |
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Where are T-cells found?
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-circulate in lymph and blood
-migrate to lymph nodes, spleen, and Peyer's patches |
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How do T-cells work?
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-in a cell-mediated immune response (no antibody secretion, act directly on:)
-endogenous invaders -many of the body's cells that harbor intracellular pathogens -abnormal host cells that produce abnormal surface proteins (cancer cells) |
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What are the three types of T-cells?
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-Cytotoxic T cells
-2 Types of helper T cells |
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Describe Cytotoxic C cells (Tc)?
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-contain hundreds of T cell receptors (TCR)
-distinguished by the CD8 cell-surface glycoprotein -directly kills |
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What do Tc cells kill directly?
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-cells infected with viruses and other intracellular pathogens
-abnormal cells, such as cancer cells |
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What distinquishes Helper T cells (TH)?
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-CD4 cell-surface glycoprotein (this is what HIV binds to)
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What is the function of Helper T cells?
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-help regulate the activities of B cells and cytotoxic T cells during an immune response
-secrete various soluble protein messengers, called cytokines, that determine which immune response will be activated |
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What are the two types of helper T cells?
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-Type 1 (TH1)
-Type 2(TH2) |
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What do Type 1 helper T cell do?
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-assist cytotoxic T cells
-express cytokine reveptor CCR5- plays a role in binding of HIV!! |
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What do Type 2 helper T cells do?
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-Activate B cells to make and secrete antibodies
-have cytokine receptors CCR3 and CCR4 |
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What are cytokines?
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-soluble regulatory polypeptides that act as intercellular signals when released from certain body cells
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What is the cytokine network?
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-the complex web of signals among all the cell types of teh immune system
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What are 5 types of cytokines?
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-interleukins (ILs)
-interferons (IFNs) -growth factors -tumor necrosis factors (TNFs) -chemokines |
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What do interleukins do?
interferons? |
-signal among leukocytes (27 to date)
-antiviral proteins that may act as cytokines |
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What do growth factors do as cytokines?
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-proteins that stumulate stem cells to divide, maintaining an adequate supply of leukocytes
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What are Tumor necrosis factors?
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-secreted by macrophages and T cells to kill tumor cells and regulate immune responses and inflammation
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What are chemokines?
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-signal leukocytes to go to a site of inflammation or infection and stimulate other leukocytes
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What are MHC antigens?
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-glycoproteins found in the membranes of most cells of vertebrate animals
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When were MHC antigens first identified?
Why are they important? |
-first identified in graft patients
-important in determining the compatibility of tissues in successful grafting |
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What is the function of MHC antigens?
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-to hold and position antigenic determinants for presentation to T cells
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Where do antigens bind to the MHC?
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-antigen-binding groove
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What are the two classes of MHC proteins?
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-MHC class I; found in most membranes
-MHC class II; only found on B cells and antigen-presenting cells (macrophages, leukocytes, monocytes) |
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What are exogenous antigens?
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-extracellular pathogens such as bacteria, fungi, protozoa
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What does APC do?
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-internalizes the invading pathogen and enxymatically digests it into smaller antigenic fragments which are contained within a phagolysosome
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What happens to the phagolysosome after pathogen is digested?
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-fuses with a vesicle containing MHCII molecules
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What happens to each fragment from the phagolysosome?
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-binds to the antigen-binding groove of a complementary MHCII molecule
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What happens to the vesicle once it fuses with phagolysosome
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-vesicle inserts the MHCII-antigen complex into the cytoplasmic membrane so the antigen is presented on the outside of the cell
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What are endogenous antigens?
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-intracellular pathogens such as viruses and bacteria
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What happens in endogenous antigen processing?
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-intracellular pathogens also digested and each fragment binds to a MHCI molecule (in ER membrane)
-membrane packaged into vesicle by Golgi body which is inserted into cytoplasmic membrane so antigen is displayed on cell's surface |
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How does the body respond to exogenous pathogens?
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-by mounting humoral immune responses
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What is the first step in humoral immune responses?
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-APC presents antigen to complementary Th cell
-CD4 binds to MHC II protein, stabilizing the TCR-antigen interaction |
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What is the second step in humoral immune responses?
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-TH cell differenetiates into a TH2 cell, cuased by IL-1 secreted by APC
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What is the third step in humoral immune responses?
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-TH2 cell binds to B cell that contains a BCR complementary to antigen (clonal selection)
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What is the fourth step in humoral immune responses?
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-the B cell MHCII binds to CD4 of TH2 cell, which leads to IL-4 secretion
-then activation of B cell proliferation into plasma cells, which produce antibodies, and memory B cells |
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What do Cytotoxic T cells respond to?
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-intracellular pathogens (viruses, intracellular bacteria) and abnormal body cells
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What is the first step in the TC cell-mediated immune response?
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-viral-encoded antigens are presented via MHC I complex
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What is step two in the Tc cell mediated immune response?
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-TCR and CD8 of Tc cell bind to MHC I-antigen complex
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What is step three in teh Tc cell mediated immune response?
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-either perforin-granzyme pathway or CD95 pathway is activated, leading to induction of enzymes that cause apoptosis (programmed cell death)
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How are T cells regulated?
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-cell-mediated immune response must be regulated to prevent T cells from responding to autoantigens
-T cells require additional signals from APC to an immunological synapse to stimulate the T cell response to the antigen |
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What are 6 ways microbes can evade immune systems?
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-capsules
-LPS modifications (O antigen) -Enzymes that degrade C5a -Proteases -Surviving phagocytosis -Antigenic variation |
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How do capsules help microbes evade detection from the immune system?
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-prevents complement activation and phagocytic killing:
1) C3bBb formation on surface inhibited 2) phagocyte receptors can't reach 3) nonimmunogenic; no opsonization for phagocytes |
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What are the two ways LPS modifications work?
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-different side chains prevent complement activation
-different side chain lengths prevent MAC formation |
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How do proteases help in immune system evading?
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-specifically degrade antibodies
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What is used for enzymes that degrade C5a in immune system evading?
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-phagocyte chemoattractant
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