Local immunostimulation of the bovine mammary gland with interleukin-2

One day after drying off, miniosmotic pumps releasing interleukin-2 were implanted into teat cisterns of six Jersey cows. Each cow had two quarters with (sensitized) and without (unsensitized) chronic Staphylococcus aureus infection. At 1 and 3 wk after implantation, three cows were sacrificed and mammary tissues processed to examine the cytological response to interleukin-2. Concentrations of lymphoid cells were determined in tissues lining teat and gland cistern linings, and plasma cells were characterized by Ig class. For total lymphoid cell and IgG1 and IgG2 plasma cell concentrations, sensitized placebo quarters and unsensitized interleukin-2 quarters were similar, indicating interleukin-2 stimulated a cellular immune response equal to that of quarters infected with S. aureus. Greatest response was observed in sensitized interleukin-2 quarters, suggesting that the cytokine was more effective in quarters with prior exposure to S. aureus antigens. Greater numbers of lymphocytes and macrophages were found in secretions of interleukin-2 quarters than in secretion of control quarters. Local interleukin-2 immunostimulation may supplement immunization procedures and enhance protection against natural S. aureus challenge.