Antibody and antigen Flashcards
What is a B-cell receptor
Membrane bound Ig on the B-cell surface
What is an antibody
Secreted Ig of the same antigen specificity as the BCR
What are antigens
foreign and endogenous substances recognized by the immune system
what is an immunogen
antigen that induces an immune response
What is immunoglobulin that is membrane bound
B-cell receptor
What is the function of immunoglobulin
Both BCR and secreted Ab bind Ag, Ag binding to the BCR signals B cell to: divide, differentiate, secrete Ab
What is the basic structure of antibody
Two identical heavy chains and two identical light chains
What are the divisions of Light chains of antibodies
Variable region (both on light and heavy), and constant region
What is a characteristic of variable region
varies between different B-cells (daughter B cells are identical)
What is a characteristic of a Constant region
Ab from same animal have similar constant region
What is a paratope
combined portion of light and heavy variable regions of antibody, 2 identical Ag binding sites per core Ab structure
What does the flexible portion on constant region of heavy chain do
allows better binding of antibody in diverse situations
What are the 5 major classes of antibody
IgM, IgG, IgD, IgE, IgA
Where are the differences in the isotypes of antibodies
in the constant region
Antibodies from the daughter cell have…..
different isotypes, but only one specificity
Characteristics of IgM
pentamer, 10 binding sites, high avidity, first Ab produced in immune response
Where is IgM found
serum and lymph
What is the first antibody produced
Igm
What does IgM do
Activate complement
How many binding sites does IgM have
10
How many binding sites does IgG have
2
Where is IgG found
Serum, lymph, and tissue
What is valence
how many binding sites on Ab are available
What is the valence of IgG
2
What is the valence of IgD
2
Where is IgD found
Surface of B-cells
What is the valence of IgE
2
Where is IgE found
mucosa (bound to mast cells and basophils)
What is the function of IgE
allergic reactions, response against helminthes
What is the most common form of IgA
dimer
What is the valence of IgA
4 (dimer form)
Where is IgA found
Mucosal surfaces and secretions (tears/milk) and serum
What does the paratope do
gives the Ab specificity for just one epitope
What is cross reactivity
Specific Ab recognizes a second similar epitope
What is the disadvantage of cross reactivity
Autoimmunity and diagnostic tests
What is and advantage of cross reactivity
Immunizations
What kind of affinity does cross reactivity have
low affinity (epitope not optimal, but good enough)
What is affinity
Binding strength between epitope and paratope
What is avidity
The sum total binding strength of all paratopes combined (ex. low affinity IgM may bind stronger than high affinity IgG because more valences[branches] so IgM>IgG avidity sometimes)
What does signaling B cell via B-cell receptor do
Divide, differentiate, and secrete Ab
What does opsonization do to antigen
enhances phagocytosis by macrophages and PMN by Fc receptors
What can Ab do to toxins/viruses
Inhibit effects of toxins/viruses by binding to it
What does Ab do to complement
begins the complement cascade
What does Ab do to mast cells and with what does it work with
Degranulates mast cells, special Fc receptors on mast cells preloaded with IgE (allergies)
What are immunoglobulin
Antigen recognition molecule of B cell
Antibodies are always part of what immune response
Active
Immune complex formation is what
Aggregation of Ag. Can be good or bad
