Medical Microbiology

TheB-CellSystem 49

Table2. 2 CharacteristicsoftheVariousImmunoglobulinClasses

IgM IgD IgG IgE IgA

Svedbergunit 19 S 7 S 7 S 8 S 7 S, 9 S, 11 S
Molecularweight 900 kDa 185 kDa 150 kDa 200 kDa 160 kDa

Numberofdimericunits 5 1 1 1 1 , 2 , 3
Hchain
(constantdomains)

l(4) d(3) c(3) e(4) a(3)

Lchain !!!!!!!!!! jork !!!!!!!!!!!

Antigen-bindingsites
(ABS)

10 2 2 2 2 , 4 , 6

Concentrationin
normalserum(g/l)

0.5– 2 0 – 0.4 8 – 16 0.02–0.50 1 .4– 4

%ofIg 6 0 – 1 80 0.002 13
Half-life(days) 1 – 2? 7 – 21 1 – 2
inserum

200 on
mastcells

3 – 6

Complement(C)activation:

Classic + – + – –
Alternative – – – – +
Placentalpassage – – + + –
Bindingtomastcells
andbasophils

– – + –

Bindingtomacrophages,
granulocytes,
andthrombocytes

– (+) – (+)

Subclasses – – +(4) – +(2)

IgGsubclasses IgG1 IgG2 IgG3 IgG4

%oftotalIgG 60 – 70 14 – 20 4 – 8 2 – 6

ReactiontoStaphlococcusproteinA + + – +
Placentalpassage + (+) + +
Complement(C)activation: +++ ++ ++++ (+)

Bindingtomonocytes/macrophages +++ + +++ (+)
BlocksIgEbinding (–) – – +
Half-life(days) 21 – 23 21 – 23 7 – 9 21 – 23

2