IgA Antibody

What is IgA Antibody?

IgA Antibody Overview and Structure quotation

IgA antibody is the most abundant antibody class in human serum and has a unique role in mediating immunity. IgA is a polyvalent antibody that is translocated to mucosal surfaces as the first line of defense against infections. Most of the secreted IgA lines the mucosal surfaces including respiratory, digestive and genitourinary tracts to protect against pathogens while maintaining gut homeostasis.

The importance of IgA in pathogen defense is highlighted by the numerous mechanisms used by pathogens to neutralize sIgAs, including sIgA-binding proteins and sIgA-specific proteases produced by certain penumococci, neisseriae and haemophilus species of bacteria.

IgA Antibody Structure and Format

IgA antibodies consists of heavy (H) and light (L) chains. Each H chain is comprised of the Constant region (Cα1, Cα2, Cα3), hinge region and the Variable (V) region. Light chains consists of the CL and Vκ or Vλ elements. Altogether the combined molecular weight of IgA antibody is ~160kDa. IgA antibodies possess a unique 18-amino acid tail piece at the C-terminus of the H chains which is key for oligomerization. As in the case of IgM antibody, IgA antibody monomers routinely dimerize with the help of a 15kDa J chain. The secreted form of IgA (sIgA) is usually dimeric and contains an additional 80-85kDa component.

IgA Antibody Schematic

Figure 1: IgA Antibody Schematic

IgA Antibody Isotypes

IgA antibody has two isotypes: IgA1 and IgA2. In human serum the ratio of IgA1:IgA2 is approximately 9:1. There are quite a few sequence differences in the two isotypes but the most profound difference is in the hinge region. IgA1 hinge regions consists of 16-18 amino acids whereas IgA2 hinge regions are much shorter at around 5 amino acids. The extended hinge region of IgA1 contains 3-6 O-linked glycosylation sites. IgA2 has two allotypes – IgA2m(1) and IgA2m(2) unlike in other antibody classes, there are no disulfide bonds linking LC and HC in IgA

IgA Antibody Mechanism of Action

Human IgA antibodies bind five different receptors that serve various functions . See table below for details.

Receptor Location Function
FcαRI Neutrophils, Monocytes
  • Binding is in the 2-5x10-7M range. Efficient activation of neutrophil-mediated phagocytosis requires FcαRI cross-linking
Fcα/μR Pre-germinal B cells, Follicular dendritic cells
  • May function in endocytosis of antigen-bound IgA
pIgR Epithelial cells, liver, lung, small intestine
  • Binding is in the 55nM range. Upon engagement with pIgR, an 80kDa polypeptide chain from pIgR (secretory component) is transferred to IgA and becomes  part of the sIgA molecule.
  • Its role is primarily prevention of proteolytic degradation
Asialoglycoprotein Liver
  • May function in clearance of IgA
Transferrin Kidney
  • May function in clearance of IgA

IgA Antibody Applications as a Therapeutic

There are two potential advantages of using IgA antibody as therapeutic.

Antibody Production at GenScript

GenScript production team scientists can produce a variety of antibody formats including IgG, IgA, IgM, Bispecific IgG, scFv, BiScFv and Fc fusion proteins. GenScript scientists perform a variety of optimization experiments and leverage years of collective experience to achieve high yields and deliver high quality antibodies to clients. A generic IgG1 production scheme is listed below followed by gel images of IgA production. In order to protect client and project information, experimental details and optimization parameters have been withheld.

Schematic of IgG Antibody Production Using Transient Expression at GenScript

GenScript IgG Antibody Production Steps

IgA Production

IgA Production

Purified IgA Antibody SDS-PAGE and Western Blot under reducing (left) and non-reducing (right) conditions.

Antibody Drug Discovery Resources and Services

IgA Antibody Overview and Structure quotation

Quotations and Ordering

IgA Antibody Overview and Structure

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