unfinished BIOC2306 Antibody structure and function

Ig domain is

stable, autonomously folding unit with conserved secondary and tertiary structure

what secretes antibodies/immunoglobulins

B lymphocytes

function of antibodies

bind antigens/epitopes

what immune response do antibodies mediate

humoral response

how many genes for typical H chain

1000 V genes

10 D genes (diversity)

4 J genes (joining)

8 C gene

the V D J make up the variable region

can have combinatorial joining and junctinal diversity to prod lot of diversity

how many genes does a typical L chain have

90-3000 V genes

3 J genes

1 C gene

variable region is V and J

what part of antibody mediates antigen binding

VH and VL

loops that project from them form antigen binding sites (where sequence variation is concentrated)

loops known as complementarity determining regions and hypervariable loops

how is further antibody diversity generated

hypermutation

how to Ig’s bid to antigen epitopes

via non covalent bonding (therefore reversible)

(H, electrostatic, hydrophobic, VDW)

function of antibodies

block interactions that antigens would have

what region of the Ab mediates its function

Fc region

how are Igs involved in phagocytosis

they opsonise antigens

Fc receptors bind Fc region of Ig-antigen complexes

phagocytosis of complexes leads to antibody degredation

what pathway do Igs activate

classical complement pathway (comp mediated lysis, comp mediated neutrilisation, phagocytosis via comp receptors)

what do neutrophils rel upon surface Ab bind target cell antigen

lytic enzymes

waht do natural killer cells rel upon Ab binding to target Ag

perforin

TNF

Granzymes

what do eosinophil rel upon Ab bidning target Ag

perforin

granzymes

waht do macrophage bind upon Ab bind to target Ag

TNF

granzymes

how do neutrophils, nat killer cells, eosinophils and macrophages bind to target cell

free Ab bind antigen on target cells

Fc receptor on immune cell binds Fc of bound Ab

hwo are immunoglobulin classes distinguished

by thier heavy chains (e.g. IgA has alpha heavy chain)

what are the 5 classes of immunoglobulins

Ig M A D G E

(all have different function)