IgA is one of the antibody members of the immunoglobulin superfamily, there are several antibody classes and subclasses (same type), antibody equivalents are determined by the molecular immunoglobulin heavy chain. The basic structure of the immunoglobulin molecule consists of two identical heavy chains (γ、μ、α、δ、ε) and two identical light chains (K or λ).IgA contains α chains that may exist in the form of serum or secretion. In the serum, 90% of IgA is monomer, while in the form of secretion, it is the main globulin present in secretions, including tears, saliva, intestinal and bronchial mucus, sweat, colostrum, and the secretion of prostate and respiratory epithelial cells, which are designed to protect the body's exposed appearance from microbial erosion. The secretion type IgA is synthesized by local plasma cells and is combined with a J-chain rich in hemispheric aureus within the cell to form a dipolymer. Monoclonal N1CLA is intended to reduce background staining of polyclonal antibodies in paraffin slices.