11. Functions Of Antibodies

Question 1

Mucosal transport of immunoglobulin

Answer 1

Secretory IgA
Dimeric transported into gut lumen thorough epithelial cells at the base of the crypts
Binds to layer of mucus overlying gut epithelium
IgA in gut neutralises pathogens and toxins

Question 2

Placental transport of IgG

Answer 2

Mother to child across placenta

Only IgG transported by FcRn

Question 3

What is phagocytosis enhanced by?

Answer 3

Ab and/or complement

Question 4

Transmembrane and soluble Ig generated by?

Answer 4

RNA splicing

Question 5

Each Ab is encoded by?

Answer 5

A specific C-region gene segment

Question 6

Antibody dependent cytotoxicity

Answer 6

Ab binds Ag on target cells
Fc receptors on NK cells recognise bound antibody cross linking of Fc receptors signal
NK cells to kill -> apoptosis

Question 7

Complement activation

Answer 7

Pentameric IgM binds to antigens adopt staple form - C1q binds and activates C1r -> cleaves and activates serine proteases
IgG binds to Ag - C1q binds to at least two

Question 8

Recognition of Fc portions of immunoglobulin

Answer 8

Fc gamma RI, RIIA, RIIB2, RIIB1, RIII : IgG 1
Fc e : E
Fc alpha R1 : IgA 1,2
Fc alpha/m R: IgA/M

Question 9

What are the diverse functions of antibodies?

Answer 9

Opsonisation and complement activation
Prevention of bacterial adhesion - antibodies block colonisation and uptake
Neutralisation of virus entry - antibody blocks binding to virus receptor and can also block fusion event, receptor mediated endocytosis of virus
Neutralisation of toxins - antibody block release of toxins and protect cells