B Cells Flashcards
What is the major function of B cells?
produce antibodies (immunoglobulins)
What is a surface immunoglobulin?
B cell antigen receptor that is membrane bound
What is valency?
number of antigen-binding sites within one receptor
What are isotypes?
various kinds of antibodies with different major functions
What are the chains of antibodies?
light chain, heavy chain
What does the hinge region do?
holds two heavy chains together by disulfide bonds
What are the aspects of the variable region?
tremendous variation determining antigen specificity, contribution from light and heavy chain form antigen-binding site, “basic unit” has 2 identical antigen-binding sites (bivalent)
What are the aspects of the constant region?
at C terminus, do NOT influence specificity
What is the Fc portion or fragment?
fragment crystalizable, confers important effector functions of secreted antibodies
What is the Fab’ portion?
fragment antigen binding, light chain and one region from both the variable and constant domains of the heavy chain, forms one complete antigen-binding site
How are the 5 isotypes grouped?
based on the constant region of their heavy chains
Which isotypes are subtyped?
IgG & IgA (General Authority)
Why do effector functions of isotypes differ?
they have different constant regions
Do variable regions influence the isotype?
NO
Do light chains influence the isotype?
NO
What isotype is rarely secreted?
IgD
What determines membrane or secreted forms of antibodies?
C terminus of heavy chain
What is a J chain?
disulfide bonds joins 5 IgM for a pentamer, and 2 IgA for dimer
What is the valence of IgM and IgA?
IgM = 10, IgA = 4
What antibody is part of the mucosal immune system?
dimeric IgA
What provides primary signal for B cell activation?
surface immunoglobulins with antigen bound