1050 Unit 2 Flashcards
what electrophoretic fraction of serum contains the majority of the immunoglobulins?
gamma phase
What are 2 characteristics of an isotype?
-located in the same species
-located in constant region of heavy chains
What are 2 characteristics of an alltoype?
-same species have allotypes present, some do not
-located in constant regions of the IgG subclasses, one IgA subclasses and the gamma light chain
What are 2 characteristics of an idiotype?
-variation in variable regions that give individual antibody molecules specificity
-located in amino acid and terminal region of heavy and light chains
Differentiate between light and heavy chains of immunoglobulins and indicate Greek letter
-heavy chain: (y) gamma, 50,000 d molecular weight, unique to IgG molecules
-light chain: 2 types –> (k) kappa and lambda (upside down y). Molecular weight is 22,000 d. found is all subclasses but only one type is present in a single molecule.
Discuss the effects of treating an immunoglobulin with papain
One or more peptide bonds in the hinge region are split. Producing 3 fragments -two Fab fragments and on Fc fragments
Discuss the effects of treating an immunoglobulin with pepsin
- cleaves the Ig above the set of disulfide bond that hold together the H chains.
-F(ab)2 created (contains 2 antigen binding sites)
-Fc portion (in nonfunctional pieces
Describe characteristics of IgG ( half life, molecular weight, amount, Greek letter)
- most abundant in serum (70-75%)
- gamma (y)
-longest half life at 23 days - monomer w/ molecular weight of 150,000 d
-4 subclasses: IgG1 (66%), IgG2 (23%), IgG3 (7%) and IgG4 (4%)
-increases with second exposure
-lab testing: precipitation and agglutination
What are the functions of IgG?
-neutralizes toxins and bacteria
-binds complement
-binds to receptors on phagocytic cells
-able to cross over to placenta
Describe characteristics of IgM (half life, molecular weight, amount in serum, Greek letter)
-muu (u) Greek letter
-“macroglobulin”
-pentamer with 10 antibody-binding sites. can also exist as a monomer
-indicates acute infection
-molecular weight of 900,000 d
-accounts for 5-10%
- half life of 6 days
-contains a J chain (joining). Forms disulfide bonds.
What are the functions of IgM?
-neutralizes toxins and bacteria
-primary antibody response
-binds efficiently to complement (complement fixation)
-causes efficient agglutination of antigens
Describe characteristics of IgA
- accounts for 10-15%
-half life of 5 days - alpha (a)
-molecular weight of 160,000 d
-monomer in serum, dimer in secretion
-2 sub classes and secretory IgA
-present in breast milk
What are the functions of IgA?
-pass immunity through breast milk
-protects mucosal surfaces and prevents bacteria adherence.
-neutralizes toxins produced by microorganisms
-acts as opsonin’s
-act as anti-inflammatory (IgA1)
Describe characteristics of IgD
-appears second, after IgM
-molecular weight is 180,000 d
-only accounts for 0.001% (rare)
half life of 1-3 days
- sigma (s)
-most susceptible to protelysis
-has extended hinge region
What are the functions of IgD?
-present as an antigen receptor on B cells (immunocompetent but unstimulated B-cells)
-role in B cell activation
-identifies mature B cells.
-
Describe characteristics of IgE
-half life of 2-3 days
-accounts for 0.005%
molecular weight of 190,000 d
-heavy chain with 4 constant regions
-(E) Greek letter?
What are the functions of IgE?
-binds to mast cells, basophils and eosinophils.
-triggers allergic reaction
-role is response to parasites, binding to eosinophils that release enzymes that kill large antigens (parasites)
-2 adjacent IgE molecules on mast cells bind a specific antigen
results in degranulation of mast cells and release of vasoactive amines (histamine and heparin)
what are some characteristics of IgG2, IgG3, and IgG4?
-IgG3–>most efficient binding complement. Induced in response to antigen proteins
-IgG2 and IgG4–> poor mediators of complement activation. involved in response to polysaccharides antigen
Describe IgA1 and IgA2
-IgA1–> acts as anti-inflammatory by downregulating IgG mediated phagocytosis, chemotaxis, bactericidal activity, and cytokine release
-IgA2–> found is secretion of mucosal surfaces (respiratory, urogenital and intestinal tract)
Describe and give characteristics of Secretory IgA
-synthesized by plasma cells
-released as a dimer held together by a J chain
-contains secretory complement (SC) derived from epithelial cells
-neutrophils, macrophages and monocytes posses specific receptors
-binding triggers respiratory burst and degranulation of cells is involved
Describe functions of the J chain and the secretory component and indicate which immunoglobulin class they are found in
- j chain–> joining
-glycoprotein that holds together monomeric units in IgM, the residue forms disulfide bonds.
-holds together 2 monomers in IgA. Essential for polymerization and secretion of IgA.
-Secretory complement–> present in IgA. derived from epithelial cells found in close proximity of plasma cells. serves as specific receptor for IgA
Discuss how IgD is different from the other types
- most susceptible to proteolysis
-does not provide protection
What type of cells do the IgE bind to in an allergic reaction?
-mast cells, basophils, and activated eosinophils
Compare and contrast the primary and secondary antibody response to an antigen
-primary –> long lag phase (4-7 days), low antibody titer (lowers in few days), low affinity for antigen
-secondary–> IgM produced, followed by a greater predominance of IgG, higher IgG titer which declines slowly over a long period of time, high affinity for antigen
Describe the genes that code for immunoglobulin proteins, and explain how they combine to code for a unique antibody molecule
-heavy chains located on chromosome 14
-light chains (kappa) located on chromosome 2
-light chains (lambda) located on chromosome 22
-Gene rearrangement–> involves cutting and splicing process that removes much of the intervening DNA, resulting in functional genes that code specific antibodies.
Describe class switching in immunoglobulins
occurs because of process called switch recombination –> portion of constant region of DNA is deleted and remaining CH genes are placed adjacent to variable region genes. This allows the same VDJ region to be coupled with a different c region to produce antibody of a different class. From IgM to either IgG, IgA, or IgE
Explain how clonal selection hypothesis contributes to antibody specificity
antigens bind only to B cells receptors specific for that antigen. Once it does, B cells are stimulated to differentiate into plasma cells that secrete antibody specificity for that antigen
outline the traditional process of mouse monoclonal antibody production.
1) mouse immunized
2) spleen cells removed
3) combine spleen cells with myeloma cells in the presence of PEG
4)select fused cells and screen for presence of desired antibody
5) grow positive cells in larger quantities
discuss some clinical and research application of monoclonal antibodies
-monoclonal antibody reagents are that they provide decreased lot to lot variations and increased specificity toward single epitope of antigen
what is a structural characteristic of the variable domain of immunoglobulins?
they occur on both the heavy chain and light chains
How does the structure of IgE differ from that of IgG
IgE has one more constant region that IgG
what does a Fab fragment consist of?
One light chain an one-half of a heavy chain
which antibody protects mucosal surfaces?
IgA
what does a typical structure of an antibody consist of?
A tetrapeptide that has two light chains and two heavy chains.
How do the subclasses of IgG mainly differ?
the arrangement of disulfide bonds.
Describe role of SC of IgA?
a transport mechanism across the endothelial cells
what is thought to be the main function of IgD?
B cell activation
which antibody is best at agglutination and complement fixation?
IgM
what is the purpose of HAT medium in the preparation of monoclonal antibody?
restricting the growth of myeloma cells
papain digestion of an IgG molecule results in what?
Two Fab fragments and one Fc fragment
what are the functions of the carbohydrate portion of Igs?
-increases the solubility of antibody
-provides protection against degradation
-Enhances functional activity of the Fc domains
what are 3 functions for complement activation?
-enhances the inflammatory response
-uses a positive cycle to promote phagocytosis
-enlists more and more defensive elements
what is neutralization?
antibodies bind and block specific sites on viruses/exotoxins which prevents antigens from binding to receptors on tissue cells
what is agglutination?
antibodies bind the same determinant on more than one antigen. cell-bound antigens are cross-linked, causing clumping
what is precipitation?
soluble molecules ae cross-linked into large insoluble complexes
What produces monoclonal antibodies?
hybridoma cells
describe cytokine storm
-massive overproduction of cytokines. It leads to shock, multiorgan failure or death.
-also called hypercytokinema
Distinguish between autocrine, paracrine and endocrine effects of cytokines
-autocrine–> same cell
-paracrine–> nearby cell
-endocrine–> systemic
Explain functions of interleukin- 1 in mediating response
-IL-1alpha and IL-1beta–> proinflammatory cytokines produced by monocytes, macrophages and dendritic cells.
-Fever
-induced by microbial components
-includes IL-1alpha, IL-1beta, and IL-1RA
Explain effects of tumor necrosis factors
- TNF-alpha–>causes vasodilation and increased vasopermeability, activates T cells by inducing expression of the MHC class II molecules, vascular adhesion and molecules. (most prominent cytokine in TNF and secreted by macrophages and monocytes)
-TNF-beta–>cause cell death of many types of cells, plays role in development of lymphoid tissues in the GI tract (produced by lymphocytes)
Discuss how interleukin-6 affects inflammation and other activities of immune response
-activates B and T cells
-produced by macrophages, monocytes, lymphocytes and nonlymphoid cells
-stimulate B cells to proliferate and differentiate into plasma cells.
-pleiotropic
-plays role in acute-phase reactions and granulocytes hematopoiesis
Determine the role of chemokines in the chemotaxis of WBC
-enhance motility of many types of WBC toward source of the chemokines (chemotaxis)
-modulate adhesion of WBCs endothelial cells lining the blood vessels, facilitating extravasation in the tissues
-classified into 4 families based on the position of N-terminal cytosine residues ( cxc, cc, c, cx3c)
-involved in inflammatory response in many diseases
what are the functions of type 1 interferon (IFNs)?
-interfere with viral replication
-activate NK cells
- enhance expressions of MHC class I protein
-IFN-alpha is produced by dendritic cells and macrophages
-IFN-beta is produced by a variety of virus infected cells.
-used for treatment of malignancies and autoimmune diseases
What are the functions of type II interferon?
-promote cell-mediated immunity (induce CDBT cells that kill infected host cells, activate macrophages to kill intercellular bacteria)
-cause antigen-activated B cells to produce IgG1 and IgG3 (opsonize pathogens and fix complement)
-includes IFN-gamma and IL-2
-produced in response to infections with viruses and intracellular bacteria
-IFN-gamma –> primary cytokine of Th1 response
Describe actions of interleukin-2 on its target cells
-drives proliferation an differentiation of T and B cells
-enhance lytic activity of NK cells
-cause naïve Th to differentiate into Th1 cells
-known as T cell growth factor
What is a general role of hematopoietic growth factor?
-stimulate proliferation and differentiation of progenitor cells in the bone marrow
-also known as CNFs
Discuss cytokines involved in differentiation of Th1
- cytokines included –> IL-2 and IFN-alpha
-IL-2 –> drives proliferation and differentiation of B and T cells , causes naïve Th to differentiate into Th1 helper cells (known as T-cell growth factor)
-IFN-alpha –> stimulates antigen presentation by class I and II MHC molecules stimulating phagocytosis and killing, regulate actions of CD4+cells, CD8+ cells and NK cells. (influences expression of more than 200 genes
Discuss cytokines involved in differentiation of Th2
-cytokines involved –>IL-4 and IL-10
-IL-4 –> promote production and inhibits Th1 cells, drives antibody responses in various diseases
-IL-10 –> inhibits antigen presentation by macrophages and dendritic cells (anti inflammatory and suppressive effects on Th1 cells, down regulate immune response by counter acting IFN-gamma (y)
Discuss cytokines involved in differentiation of Treg Cells
-cytokines involved–> TGF-beta and IL-10
-Both –> down regulate immune response to prevent chronic infection, helps establish peripheral tolerance to self-antigens and harmful antigens, may prevent tumor cells from attack by inhibiting cancer-fighting cells
Discuss cytokines involved in differentiation of Th17
-cytokines included–> IL-17
-role in host defense against bacterial and fungal infections at mucosal surface
-promote release of antimicrobial peptides
-promote recruitment of neutrophils
Explain the biological role of colony-stimulating factors (CSFs)
responsible for inducing differentiation and growth of all WBC types
Describe types of anti-cytokine therapies
- anti-cytokine therapies target chronic inflammation
-disrupting interaction of between cytokines and their receptors (infliximab)
-using monoclonal antibodies that function as cytokine antagonist
-blocking IL-17 function
-hybrid proteins attached to Ig constant regions to block cytokine activity (etanercept)
describe clinical assays for cytokines
-ELISpot assay –> a technique similar to ELISA performed on in vitro-activated peripheral WBCs
-multiplexed ELISAs –> can detect many pro- and anti- inflammatory cytokines in one reaction
-Microbead assay–> allow for the simultaneous detection of multiple cytokines and other biomarkers in a single tube
What is the ability of a single cytokine to alter the expression of several genes called?
pleiotropy
what is an effect attributed to IL-3?
mediation of innate immune response
what are the precursor target cells for IL-3?
-myeloid precursors
-lymphoid precursors
-erythroid precursors
What will happen if there is a lack of IL-4?
decreased eosinophil count
which of the following cytokines is also known as T cell growth factor?
IL-2
IFN-alpha and IFN-beta differ in which way from IFN-gamma?
-IFN-alpha and IFN-beta inhibit viral replication
-IFN-gamma stimulates antigen presentation by class II MHC molecules
A patient in septic shock cause by a gram-negative bacterial infection exhibits high fever, very low BP, and disseminated intravascular coagulation. Which cytokine is most likely contributing to these symptoms?
TNF
IL-10 acts as an antagonist to what cytokine?
IFN-gamma
Selective destruction of Th cells by the HIV virus contributes to immune suppression by which means?
decrease in IL-2
why might a CSF be given to a cancer patient?
increase production of certain types of leukocytes
what is the best assay to measure a specific cytokine
ELISA testing