[Passive protective activities of human sera against infection with strain ST67P of Staphylococcus hyicus].

Five tenths ml of passive protective antibodies in 100 samples of normal human sera against challenge with an encapsulated strain ST67P of Staphylococcus hyicus in mice were examined. Thirty three of them passively protected in mice against infection with strain ST67P of S. hyicus. The activities were sensitive to 2-mercaptoethanol and were absorbed out either with rabbit anti-human IgG, IgM or IgA serum. Also, the serum activities were absorbed out with cell surface polysaccharide extracted from the cell surface substance of the strain. When passive protective human serum was absorbed out with cell surface polysaccharide, reduction of IgG, IgA and IgM contents were 14.48, 19.49 and 33.3 percent, respectively, while 2.17, 4, 55 and zero in non protective human serum. These results indicate that the protective activities against strain ST67P were specifically related to IgM globulin against the above cell surface polysaccharide.