What is IgA Antibody?
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.
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.
- Binding is in the 2-5x10-7M range. Efficient activation of neutrophil-mediated phagocytosis requires FcαRI cross-linking
||Pre-germinal B cells, Follicular dendritic cells
- May function in endocytosis of antigen-bound IgA
||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
- May function in clearance of IgA
- May function in clearance of IgA
IgA Antibody Applications as a Therapeutic
There are two potential advantages of using IgA antibody as therapeutic.
- Mucosal target: If the site of action is mucosal rather than in the blood, a dimeric sIgA may be a suitable approach. An advantage of sIgA in a mucosal setting is the protection from proteolytic damage, offered by the secretory component (SC) which physically wraps around the IgA Fc region.
- FcαRI binding: The ability of IgA to bind FcaRI found on neutrophils and other cytotoxic immune cells allows neutrophil and monocyte-dependent phagocytosis.
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.
GenScript IgG Antibody Production Steps
- IgG Antibody Gene Synthesis and Subcloning: After customer's approval, target DNA sequences are designed and synthesized. Synthetic genes are subcloned into a GenScript proprietary vector for expression.
- IgG Antibody Cell Culture and Transient Transfection: Typically, GenScript scientists use either HEK293 or CHO cells, for recombinant antibody expression . Cells are grown in serum-free media. Recombinant plasmids encoding H and L chains are transiently co-transfected to suspension cell cultures. Cell culture supernatant is collected on day-5, post-transfection for SDS-PAGE analysis, in order to evaluate expression levels.
- IgG Antibody Purification and Analysis: Purification is carried out using protein A column. Eluted fractions are analyzed by SDS-PAGE and Western blot and pooled and buffer exchanged to the final storage buffer.
- Deliverables: Synthetic genes in pUC57 vector, optimized gene sequence report and purified antibody at listed amount and purity were delivered to the client along with QC data and comprehensive report.
Purified IgA Antibody SDS-PAGE and Western Blot under reducing (left) and non-reducing (right) conditions.
Antibody Drug Discovery Resources and Services
Antibody Discovery: GenScript has over 10 years of experience in therapeutic antibody development, offering a variety of services in the early therapeutic antibody discovery phase. For example, GenScript's Antibody Engineering group can build antibody library with up to 1010 individual clones, to speed up your antibody discovery efforts.
Antibody Sequencing: GenScript's advanced Antibody Sequencing technology offers fast and professional sequencing services for your monoclonal antibodies.
Assays: GenScript has developed several cell-based ADCC/CDC functional assays to profile the efficacy and potency of your therapeutic antibodies using proprietary recombinant effector cells.
Antibody Engineering: GenScript scientists' extensive experience in antibody engineering can provide superior services such as antibody humanization, affinity maturation and more.
Antibody Production: With solid expertise in recombinant antibody (rAb) production techniques, GenScript provides a comprehensive rAb service portfolio that deliver microgram to gram quantities of pure rAb for each stage of your Ab drug discovery program.
PK/PD Study: GenScript offers over 120 tumor and inflammation models for evaluation of in vivo efficacy, PK/PD, biomarker and bioanalysis studies. GenScript
Anti-idiotype Antibody services are also a powerful tool for antibody drug PK/PD and immunogenicity studies.
- You can also view our
Recombinant Antibody Service Selection Guideto identify services that are the best match for your application.
Quotations and Ordering
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