%0 Journal Article %A Yoshida, K. %A Ichiman, Y. %A Narikawa, S. %A Takahashi, M. %A Kono, E. %A San Clemente, C. L. %T PASSIVE PROTECTION BY HUMAN SERUM IN MICE INFECTED WITH ENCAPSULATED STAPHYLOCOCCUS AUREUS %D 1979 %J Journal of Medical Microbiology, %V 12 %N 3 %P 277-282 %@ 1473-5644 %R https://doi.org/10.1099/00222615-12-3-277 %I Microbiology Society, %X SUMMARY The occurrence and nature of passive protective antibody in 100 samples of human serum was investigated in mice challenged with strains of Staphylococcus aureus capsular types A (Smith diffuse strain) and B (strain NS58D). Sixty of the sera passively protected mice against the capsular type-A strain, three against type B, and one against both types. Rabbit antisera against human IgG, IgA and IgM could remove the protective activity from a human serum of high potency, and the activity was also sensitive to 2-mercaptoethanol. Absorption with Smith surface antigen removed protective activity and reduced the concentration of IgG 7-fold, IgA 2.7 fold and of IgM 3-fold more than in a non-protective serum. Consequently, the protective activity of human serum is believed to be associated with antibodies to the S. aureus capsular antigen in the three immunoglobulin classes. %U https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-12-3-277