Immunology Lecture 4_Antibodies Flashcards
Define Immunoglobulin (antibody)
Immunoglobulins (IgX) are protiens that are secreted by B cell lymphocytes to neutralize pathogens. They do this by by binding to a pathogen or it’s products and recruting other leukocytes to destroy the pathogen.
Identify the following structures on an IgX: Heavy chains, light chains, constant region, veriable region, flexible hinge (what tertiary bond forms this), antigen binding site, C terminus and N terminus, Fc, and Fab
Draw a picture, refer to slide 5 if needed
What does the Fab region do?
Fragment Antigen Binding (Fab) is the part of the IGX that binds to the epitope on the antigen (they are epitope specific)
What does the Fc region do?
Fc binds to Fc receptors on other cells, often to iniciate phagocytosis
Define Autoantigen
A self molecue that incorrectly induces an immune response
Explain combinatorial diversity
recombination activating gene (RAG) mediates multiple V -(D)-J combinations in the veriable protion of the heavy and light chains.
Define Junctional diversity
Additions and deletions of necleotides at junctions durring recombination.
Define valence
Valence is the number of pathogen binding sites. A single anti body has a valence of 2
Define Affinity
The strength of binding at a single site
Define Avidity
Total strength when all binding sites are included (Avidity increases as valence increases similar to the strength of a rope as you add strands)
What kind of IgX do naive B cells have as BCR
both IgM and IgD
What kind of IgX do memory b cells express as BCRs
they can express any one isotype as a BCR
Where is the IgG isotype high?
in blood and epithelial tissue
Where is the IgA isotype high?
at the mucosal surfaces
How is the Classical Complement Cascade triggered?
It is triggered with one Pentameter of IgM or at least 2 monomers of IgG
Describe Opsonization. What IgX typically triggers it
Antibodies bind bind to a pathogen and then Fc receptors on phagoctotic cells bind to the Fc end of the antibody and begin phagocytosis. This is typically meadiated by IgG
Describe Antibody dependent cellular cytotoxicity (ADCC). What IgX meadiates it
Viral infected cells express antigenic protiens on their surface. Antibodies bind to these cells then bind to NK cells via Fc receptors. NK cells are triggered to kill the infected cell. This is typically mediated by IgG
How do IgXs interact with mast cells. What IgX is envolved
IgEs bind to mast cells via Fc receptors. when the IgE binds to an antigen, it trigers a massive release of hisamine from the mast cell.
How do IgXs interact with eosinophils? What IgX is envolved?
IgEs opsonize a parasite. Then eosinophiles bind to the IgE coated parisite via Fc receptors and are triggered to degranulate.
How does IgM exist in the body as both a BCR and secreated protein?
exists as a monomer in the BCR form and a pentamer in the secreted form
What is the first antibody formed during a primary response?
IgM
Describe Hyper IgM
It is a rare disorder where a person has elevated levels of IgMs. This leads to increased decreased rates of other isotypes which leads to dificult to treat infections
What is the function of IgD
The function of IgD is unclear. It has very low serum consentrations. Higher rates of IgD producing plasma cells are found in the respiratory tract as compared to the digestive tract
Describe neutralization
it is when secreted antibodies bind an antigen and prevent it from passing through its target barrier. IgA prevents antigens from crossing epithelial barriers and IgG prevents antigens from entering target cells
List the 4 functions of IgG and what part of the immune respons it participates in
the four functions are Nutralization, opsonization, complement activation (of the classical pathway) and ADCC. It is the predominante isotype in the late primary and memory response
Where does IgA exist as a dimer/monomer? How abundent in blood, where else is it found.
IgA exists as a monomer in blood and a dimer in secretions. It composes 10-15% of serum IgXs and is the predominant IgX in secretions including saliva, tears, and breast milk.
What is a likely out come of antibody deficiencies?
recurrent pyogenic infections and difficulty with encapsulated bacteria
