Immunoglobulin G (IgG) is the most abundant immunoglobulin in serum and is predominately involved in the secondary immune response. The IgG subclasses are designated 1, 2, 3 and 4 based on their relative prevalence in serum. The sensitive quantitative measurement of total horse IgG 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 IgG subclasses. The kit does not cross react with human, mouse, rat, dog, sheep, pig, rabbit or monkey at the recommended dilution. The concentration of IgG in normal adult horse serum is 19.13 mg/ml. The assay measures horse IgG in the 0.2-200 ng/ml range. Samples giving horse IgG levels above 200 ng/ml should be diluted in blocking buffer before use. A 1:2,000,000 to 1:16,000,000 dilution for serum is suggested for best results. Horse IgG will bind to the capture antibody coated on the microtiter plate. After appropriate washing steps, peroxidase labeled anti-horse IgG 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 horse IgG in the samples. A standard calibration curve is prepared in blocking buffer using dilutions of purified horse IgG and is measured along with the test samples. All reagents and standards are provided in these ELISA kits.