6. Antibodies Flashcards
Give a quick overview of immunoglobulins. What are they also called? What part of the immune system are they? Produced by?
AKA antibodies
Part of humoral immune system
prod by plasma cells - derived from B cells
diff types w/ diff purposes
importance - host defence, vx, testing
What is the importance of antibodies?
used diagnostically to detect infection -> rising titers (means higher serum antibody lvls and recent infection)
Also used to fight infections -> vx’s boost antibody titers - often the basis for judging effectiveness. Hyperimmune sera may be prescribed to treat infections
What is the basic immunoglobulin structure?
All immunoglob molecules have same basic y shape w/ hinge region.
Stalk/tail of Y is crystallizable fragment (Fc) - constant within antibody class, determines class, responsible for effects of Ig when head binds to antigen
Top of Y is TWO antigen binding fragments (Fab) - composed of both constant/variable regions. A given clone of plasma cells (daughters of a common B cell) prod an Ig that is specific for one particular antigen
How does immunoglobulin function?
Fc mediates binding to; Host tissues, various cells of immu system, 1st component of complement system
Fab binds antigen specifically - marks antigen for immunological attack, activates non-specific defense mechanisms that can destroy antigen ex. opsonization for enhanced phagocytosis
Where is the site of production for immunoglobulins?
Ig are prod by B cells and Plasmacells
B cells put Ig on their surface
Plasma cells excrete ig into body fluids - lymp -. drains into vascular systems
What are the differnt types of immunoglobulins?
4 types/classes - IgM, IgG, IgE, IgA,(IgD)
Each type can bind to the same antigen Ag
the distribution of antibody and effects of binding vary with the type
Describe how IgM’s are produced? What do they look like? What are their protective actions?
All B cells initially prod IgM and gradually switch to prod the other Ig’s
Loks like 5 Ig molecules joined together, a big molecule so only in blood, lots of binding sites though each is weak
Protective actions - efficient at agglutination (binding antigen together) may precipitate antigens
What is the function of IgM?
neutralization - binds to antigens making them ineffective. Pathogenic bact have specialized structures to attach to host cells but are blocked by antibody
Complement activation - classical pathway = inflam, opsonization, Membrane attack complex
What is the functions of the 4 most common Ig’s
IgM - Neutralization, Complement activation
IgG - Antibody mediated defense, agglutination of antigens, neutralization, complement activation, opsonization by direct binding, Ig-depended cell mediated cytotoxicity
What is IgG? What does it do for the immune system?
As immune response matures + becomes efficient - B cells switch from IgM to IgG (so do plasma cells)
Major antibody of serum
Smler than IgM so can reach sites of inflam more easily(igG is principal antibody of tissue fluids)
What is the function of IgG?
Antibody mediated defense
agglutination of Ag’s (not as effective as IgM)
Neutralization - binds tighter than IgM, blocks adhesion sites on pathogens, binds/blocks toxins
Complement activation - classical pathway (req 2 IgG’s to be bound)
Opsonisation + antibody dependent cell mediated cytotoxicity
How does IgG use opsonization by direct binding? What about antibody dependant cell mediated cytotoxicity?
- Opsonization by direct binding - Ig head binds to antigen ex on surface of bact, Ig tail changes shape, can now bind to phagocytes - engulf antigen the IgG attached to
Ig-dependent - some pathogens too big to engulf (cells w/ virus’), instead antigen-IgG complexes binds NK cells to kill infected cell
Antigen-antibody complexes may bind to neutrophils + eosinphils and stim to release oxidants
What is veterinary application of IgG + IgM?
serial measurements of Ig to determine if a pathogen is the underlying cause of clinical signs in the patient - serial Ig measurements
IgM will inc w/ acute infection
IgG will inc during acute infection
titer test importation of animals - rabies
Describe IgA, how does it work?
major antibody of mucosal surfaces - GI, Respire - gut lymphoid tissue is a major site of IgA prod
Secreted as a dimer with secretory pieces - transport tag for epithelial cells, confers resistance to digestive enzymes
more IgA prod in day than all others combined (only sml amount in serum)
works by neutralization (viruses, prevents microbes from binding)
agglutination
cannot activate phagocytes, does not bind complement
What produces IgE? Where does it bind?
Mainly prod by plasma cells just below body surface
most binds to surface of basophils + mast cells in tissues b4 binds to antigen
IgE is sentinel antibody
Antigen binding causes release of granules - triggers acute inflam, important in parasite defense, important in allergies - immediate hypersensitivity
