B Cells Flashcards
Humoral immunity is mediated by …..
B lymphocytes and CD4+ T helper cells
Cellular immunity is mediated by…….
CD8+ cytotoxic T cells and CD4+ T helper cells
What is protein in antibody?
Immunoglobulin (Ig)
Antibody is tetrameric
What does this mean?
2 identical heavy chains and 2 identical light chains are held together by non covalent interactions and s-s cross links between cysteine amino acid residues
What are 2 types of light chain?
Kappa (K) chain
Lambda chain
What is constant region?
Amino acid sequence varies from one Ig molecule to another
What is variable region responsible for?
Responsible for effector functions
How many antigen binding sites do Ig molecule?
2 antigen binding site
What does Fab antibody fragment stand for?
Fraction antigen binding
What does Fc antibody fragment stand for?
Fraction crystallisable
What is a region of Ig molecule other than antigen binding site?
Flexible hinge region
How does antibody fight infection?
By coating + neutralising pathogen
By activating complement
By opsonisation
How does antibody bind to antigen?
Via non covalent interactions e.g. electrostatic, hydrophobic, VDW forces and H bonds
What is an epitope?
Binding site on antigen for one specific antibody
What does B cell activation require?
Antigen binding site to B cell receptor (mIgM) resulting in stimulation of signal transduction pathways
Co stimulation by T cells
What happens when a B cell is activated?
It multiplies rapidly
Differentiates to become Ig secreting cells
First make IgM
Then undergo class switching to make Igs with same antigen specificity i.e. antigen binding site but different heavy chain constant regions e.g. IgG, IgA etc
What does activated B cell differentiate into?
Ig secreting cells e.g. plasma cells or memory B cells
