Localized immunity in experimental bovine mastitis caused by Mycoplasma dispar

Development of immunity to reinfection with Mycoplasma dispar occurred in the bovine mammary gland and appeared to be confined to the quarter or quarters previously infected with this mycoplasma; it was not generalized throughout the gland. Immunity followed the inoculation of virulent strains of M. dispar but not of an avirulent strain. The immunity engendered protected against both homologous and heterologous strains of M. dispar. Challenge of immune quarters with virulent M. dispar resulted in a transient polymorphonuclear cell response greater than that observed in previously uninoculated quarters.