Proteins are an important part of building up of immune system. Major histocompatibility complex-III is a set of cell surface type proteins that is required for immune system that is acquired, to help in recognizing foreign molecules that are present in vertebrates. Specifically located on chromosome 6 in humans, and chromosome 17 in mouse, there are complex 2 and complex 1 aspects of this protein that are required for detecting foreign bodies in higher beings.

Major histocompatibility complex-III protein is specifically found in all higher beings. This complex is specifically known as human leukocyte antigen (HLA) system. In case of class III molecules, these proteins are specifically restricted to immune systems of lymphocytes and macrophages. All these molecules are clustered around chromosome 6 in humans. In case of humans, they detect infection related microorganisms that are ingested within human body. With Mouse major histocompatibility complex-III (MHC-III) ELISA Kit further tests are being conducted on mice as backup.