To obtain reagents required for the purification, identification and diagnosis of disease, a monoclonal antibody (mAb) specific to equine serum proteins was prepared by cell fusion. Thirty seven hybrid cell lines that secrete mAb specific to eight serum proteins (Al, Es, Hp, Tf, IgG (T), IgG, IgM and α2-M) were produced. Changes in serum components could be readily detected by Western blotting with mAbs.