Immunization and immunity

The defense mechanism of the mammary gland is a complex system in which each component's function is not independent of the other. The various components of nonspecific resistance, antibody production and cell-mediated immune response can act to the benefit or detriment of the host. Our ability to predict and control each of these responses is limited. Zealous efforts to enhance one area irrespective of the others may not work to the benefit of the animal. High antibody levels have not always provided protection against mastitis, whereas cell-mediated responses may produce either a beneficial or harmful hypersensitivity response. Until antigenic effects are better understood and product safety is assured, vaccination against mastitis will be limited in its beneficial value. The use of biologic products may eventually become a practical approach in controlling mastitis by maintaining herd resistance; however, these products are no substitute for a good mastitis control program of teat dipping, dry-cow therapy, milking-equipment maintenance, proper milking sanitation, and good milking practices. Mastitis control cannot be purchased in a bottle.