What are the differences between IGA and IGG?

Basis of Differentiation

IGA

IGG

Is an antibody present in secretions and mucous membranes and acts against bacterial and viral pathogens

Is an antibody produced as a secondary immune mechanism involved in fighting against pathogenic viral and bacterial strains

Subclasses

has 2 subclasses

has 4 subclasses

Structure

Monomer or dimer

Monomer

Distribution 

Is in mucous membranes and body secretions such as saliva and breast milk

Is in all intra and extravascular tissues

Concentration of heavy chain

Has Alpha heavy chain

Has Gamma heavy chain

Concentration in serum

In serum, iga concentration is 0.6 – 3 mg /ml

In serum, igg concentration is 6-13 mg/ml

J chain 

Present 

Absent

Secretory polypeptide

Present 

Absent

Ability to cross the placenta

Cannot cross the placenta

Can cross the placenta

Functions

expressed in mucosal tissues, preventing colonization

highest opsonization and neutralization activities