Immunophysiological activity of supramammary lymph nodes of the ewe during the very early phase of staphylococcal mastitis.

Efferent mammary lymph was collected from lactating ewes which were unimmunised (controls) or immunised during pregnancy with two doses of an attenuated live Staphylococcus aureus vaccine either in the hindlimb ("directly primed' supramammary nodes) or in the brisket ("indirectly primed' supramammary nodes). Mammary lymph was also collected from unimmunised animals in which the supramammary nodes had been extirpated several months before. Ewes in which the supramammary nodes had been directly primed by staphylococcal vaccination before challenge had a significantly greater output of IgM- and IgG2-containing cells in lymph and higher concentrations of IgG1 and IgG2 antibody against S aureus surface antigens than did other groups. Lymphadenectomised ewes had fewer leucocytes in mammary lymph but a much higher proportion of neutrophils than other ewes, indicating that afferent mammary lymph has an unusually high number of neutrophils and most of these cells are filtered out in the supramammary lymph nodes under normal circumstances. The results indicated that most of the leucocytes in efferent lymph were derived from the supramammary nodes. After induction of experimental staphylococcal mastitis there was a rapid drop in leucocyte output in lymph within one to four hours after infection; the data indicated that events within the supramammary nodes were responsible for this phenomenon. The output of immunoglobulin-containing cells was reduced during this phase. No significant increases in output of lymphoblasts, immunoglobulin-containing cells or specific antibody occurred during the six hours immediately following infection.