Human Immunoglobulin A (IgA) is the most abundant immunoglobulin in body fluids and the second most abundant immunoglobulin in plasma. IgA in serum is a primarily monomeric 160kDa glycoprotein that initiates defenses against natural infection through interaction with specific receptors and immune mediators. Each monomer consists of two heavy chains and two kappa or lambda light chains. A majority of serum IgA molecules are subclass IgA1 which have longer hinge regions than subclass IgA2. The sensitive quantitative measurement of total human IgA antigen in serum, plasma, hybridoma cell supernatants, ascites or other biological fluid samples is easily performed with this 96 well strip format ELISA kit. The assay does not distinguish IgA subclasses. The concentration of IgA in normal human serum ranges from 0.7 to 4.0 mg/ml. The assay measures human IgA in the 0.1-100 ng/ml range. Samples giving human IgA levels above 100 ng/ml should be diluted in blocking buffer before use. A 1:100,000 to 1:800,000 dilution for normal human serum or plasma is suggested for best results. Human IgA will bind to the affinity purified capture antibody coated on the microtiter plate. After appropriate washing steps, peroxidase labeled anti-human IgA primary antibody binds to the captured protein. Excess antibody is washed away and TMB substrate is used for color development at 450nm. Color development is proportional to the concentration of human IgA in the samples. A standard calibration curve is prepared in blocking buffer using dilutions of purified human IgA and is measured along with the test samples. All reagents and standards are provided in these ELISA kits.

The human IgA standard provided in this kit is calibrated against the WHO International Standard for Human Serum Immunoglobulins G, A and M (NIBSC Code 67/086).