Assignment 4 Flashcards
List the antibody isotypes and provide the greek name of the heavy chain constant region that define each
IgG - gamma IgM - mu IgA - alpha IgE - epsilon IgD - delta
what are the 2 constant regions on the light chain?
kappa and lambda
structure and function of light chain?
structure - variable (important for binding antigen) and constant regions constant region (kappa/lambda)
single Antibody will either have two kappa constant regions or two lambda constant regions but not one of each! -
structure and function of heavy chain?
structure - variable and constant regions constant regions • α-IgA1,2 • δ-IgD • γ-IgG1,2,3,4 • ε-IgE • μ-IgM
describe the products of enzymatic digestion with papain and explain how the results of these products revealed the structure and function of antibody molecule
IgG + papain–> two F(ab) [2Fab/2F(ab)] + Fc (intact)
Digestion yields two copies of a single Antigen binding region F(ab) and one fragment Fc that
cannot bind antigen
describe the products of enzymatic digestion with pepsin and explain how the results of these products revealed the structure and function of antibody molecule
IgG + pepsin—>Fab2 + degraded Fc
Digestion yields one molecule with two Ag binding sites Fab2. The Fc portion is degraded.
what is the “biological activity” of an antibody?
The ability of an antibody to bind to receptors on phagocytes, mast cells, or basophils and the ability to activate the complement pathways.
Resides in the Fc portion of an antibody molecule.
biological activity differences are a result of aa differences in the constant region, although the basic molecular structure of the molecule is the same.
explain the term allotype using Km, Am and Gm
antigenic differences w/in a given class of Ig between members of the same species
Am – the IgA allotypes
Gm – the IgG allotypes
Km – the kappa chain allotypes
define the term subclass as it relates to IgG and IgA
refers to the variation in IgA and IgG in each individual
subclass within the antibodies (IgG1, IgG2, IgG3. IgA1, IgA2)
define affinity
the force between molecules that impels them to bind to one another (non-covalent)
define avidity
the sum of affinities
describe the nature of the bonds that allow an antigen-antibody interaction
involved both hydrophobic and ionic components
what cells express Fc portion of IgG (Fc gamma R)
NK cells
neutrophil
monocyte
B-cell
what is the difference between dimeric IgA and secretory IgA?
dimeric IgA - is in lamina propria - dimeric IgA is converted to secretory IgA secretory IgA -is present in lumen
- disulfide bonds differentiate subclasses
how does dimeric IgA become secretory IgA?
dimeric IgA is on basolateral side of epithelial cell
–> binds to secretory component and is internalized in epithelial cell –>secretory components cleaved and released into lumen
define crossreactivity
refers to fact that some antibodies will bind to antigens that have similar or same
epitope
define crosslinking
when two antibodies bind to an antigen epitope
what are monoclonal antibodies preparations?
antibodies that are identical because they were produced by one type
of immune cell and are all clones of a single parent cell
what are polyclonal antibodies preparations?
antibodies that are derived from different B-cell lines. They are a mixture of immunoglobulin molecules secreted against a specific antigen, each recognising a different epitope.
how is a hybridoma generated?
cell that is the result of fusion of a tumor cell with a normal cell
used to manufacture antibodies
define idiotope
antigenic determinants (idiotopes)
hypervariable regions can serve as
define idiotype
collection of idiotopes in a given antibody
explain what is meant by “anti-idiotypic antibodies”
antibodies generated to the collection of idiotopes on a single antibody molecule
explain what is meant by “anti-isotypic antibodies”
when animal antibodies are generated that recognize the human antibody Fc region/constant region
explains why/how an Rh- mother carrying an Rh+ child poses a risk to the fetus
first pregnancy is ok since no anti Rh antibodies have been made
second pregnancy will compromise fetus unless treated–>hemolytic disease of newborn
what cell secretes antibodies?
B cells - plasma cells
what do antibody units consist of?
2 identical light chains covalently bonded to 2 identical heavy chains
what do each light and heavy chain have?
variable region (N terminal) and a constant region (C terminal)
what is the predominant light chain?
kappa
what is allotypy?
presence of allelic forms of the same protein in the population - this is what kappa light chains demonstrate!
what are hypervariable regions?
region within the variable regions - differ extensively!
represent aa sequences that are unique to a particular antibody and complementary to a particular antigenic epitope ( part of an antigen that is recognized by the immune system)
aka complementary determining regions (CDRs)
what do complementary determining regions (CDRs) form?
paratope - part of the variable region that contacts the epitopes ( part of an antigen that is recognized by the immune system) on the antigen
what 2 areas do antibodies possess?
antigen binding capacity
biological activity region
*initially demonstrated following proteoloytic cleavage of antibody
what defines the antigen binding sites?
the combined variable regions of the light and heavy chains
*there are 2 identical binding sites on each monomeric antibody molecule
what is the Fc region determined by
the constant region of the antibody
what is the function of secretory IgA?
immunosurveillance - bind to organisms before they bind to M cells, their port of entry into the Lamina propria
also acitvates the alternative pathway of complement
