Immunoglobulin A (IgA) is the main immunoglobulin in mucous secretions and the second most abundant immunoglobulin in serum. It defends against inhaled and ingested pathogens by binding an Fc receptor on myeloid leukocytes. The equivalent mouse receptor has not yet been identified. Human IgA has two distinct subclasses and is monomeric in serum while mouse IgA does not have subclasses and is dimeric in serum. The sensitive quantitative measurement of total mouse 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 kit does not cross react significantly with rat, pig, sheep, dog, rabbit, cyno monkey, rhesus monkey, or human IgA. The concentration of IgA was found to be 0.4 mg/ml in NIH Swiss mouse serum and 0.7 mg/ml in BALB/C mouse serum. The assay measures mouse IgA in the 0.1-100 ng/ml range. Samples giving mouse IgA levels above 100 ng/ml should be diluted in blocking buffer before use. A 1:200,000 dilution for serum is suggested for best results. Mouse IgA will bind to the capture antibody coated on the microtiter plate. After appropriate washing steps, peroxidase labeled anti-mouse 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 mouse IgA in the samples. A standard calibration curve is prepared in blocking buffer using dilutions of purified mouse IgA and is measured along with the test samples. All reagents and standards are provided in these ELISA kits.