6: Antibody structure Flashcards
3 main functions of antibodies
- opsonization
- complement activation
- neutralization
opsonization examples (2)
- phagocytosis
- eosinophil dumps toxic products to kill parasite
- coating antigen with antibody enhances phagocytosis
complement activation
series of proteins activated by antibody binding to surface –> punch holes in bacteria
-inflammation and cell lysis
neutralization
secreting products onto virus/bacteria to block adhesion to mucosa
what is adaptive/acquired immunity
the specific response to antigenic challenge
what is adaptive immunity mediated by
antigen-specific lymphocytes and/or their products
5 steps of the immune response
- innate immunity
- early induced response
- late adaptive response
- protective immunity
- immunological memory
steps of innate immunity
innate immunity –> infection –> recognition by non-specific effectors –> pathogen clearance
steps of early induced response
early induced response –> infection –> recruitment of effector cells –> activation of effector cells –> pathogen clearance
steps of late adaptive response
late adaptive response –> infection –> antigen transport to lymphoid organs –> recognition by native b and t cells –> clonal expansion of b and t cells –> pathogen clearance
steps of protective immunity
-protective immunity –> re-infection –> recognition by preformed antibody and effector t cells –> pathogen clearance
steps of immunological memory
immunological memory –> re-infection –> recognition by memory b and t cells –> rapid expansion to effector cells –> pathogen clearance
when does antibody production initiate
3-7 days after initial exposure if the innate immune processes fail to clear it rapidly
what are antibodies
antigen-specific products of b cells –> principal mediators of adaptive immunity
antibody structure
- 2 identical heavy chains, 2 identical light chains
- variable and constant regions
- 2 binding sites on top of light chains
how do antibodies interact with antigens
non-covalently
how are antibodies divided into isotypes (classes)
different constant regions –> heavy chain weight gives different properties (heavy chain is the constant region)
types of antibodies made by b cells
- different b cells make different antibodies
- a single b cell makes all the same antibodies
how are distinct antibody regions determined
by protease digesion –> Fc portion contains heavy chain constant region, Fab portion contains the antigen binding site
what are Fc and Fab
- Fc: fragment of crystalization
- Fab: fragment of antigen binding
how are different antibody regions defined
- proteolytic digesion
- function
where are antibodies assembled
in the b cell
where does antigen binding occur
binding site at junction of variable heavy chain and variable light chain
valency of antibodies
multivalent –> can bind 2 of the same epitopes on a single antigen or 2 of the same epitopes on different antigens
types of antibody differences (3)
- isotypic differences (IgG v IgA)
- allotypic differences (different alleles but both IgG)
- idiotypic differences (binding site differences)
difference between b cell and mature plasma cell
- b cell has antibodes on cell surface
- plasma cell secretes antibodies
- plasma cell is a b cell that secretes antibodies
what immunoglobulin is always secreted first by a b cell
IgM
what Ig are secreted onto mucosal surfaces and protected from degradation by binding to the J chain
IgM and IgA
how are IgM and IgA secreted
- IgM as a pentomer
- IgA as a dimer
- antigen specificity of antigen binding site is identical for both
purpose of J chain
used to transport dimeric IgA across epithelial barriers to coat mucosal surfaces
what does the variable region confer
epitope specificity
what does the Ig constant region confer
functional capacity
what does allelic exclusion result in
only 1 chromosome rearrangement per cell
what is IgM known for
complement activity
what is IgD known for
not fucking much
what is IgG known for
basically everything (opsonization, crosses placenta, extravascular diffusion) –> phagocytosis
what is IgA known for
mucosal –> crosses epithelium
what is IgE known for
mast cell activation
what are isotypes encoded by
a cluster of heavy chain genes
what influence which isotype is expressed
cytokines
consequences of inherited IgA deficiency
no antibodies on lung surface –> URI
what connects variable and heavy chains together
hinge –> gives flexibility
how is the region of the antibody gene that binds to the epitope generated
by a semi-random rearrangement of gene segments –> different exons for the antibody chains within each b cell (more variation = more things recognized)
