Normally Occurring Staphylococcal Antibodies in Germfree Mice

The sera of nonimmunized mice from both germfree and nongermfree colonies of similar genetic stock have been shown to have antibodies for staphylococci, by serum-gel diffusion, agglutination and fluorescent antibody tests. In general, agglutination titers were higher in conventionally reared animals than in germfree animals, and higher in 8-month-old animals than in 2-month-old animals. When pooled samples of serum from 8-month-old germfree mice were labeled with fluorescein isothiocyanate, some strains of staphylococci were stained in high dilutions of the labeled serum. The results indicate that several different antibodies for staphylococci were present in the sera of 8-month-old germfree and conventional mice. Two of the antibodies observed by reactions in gel-diffusion plates were related to previously reported activities. One of these substances is antibody to antigen A of Jensen, previously reported to occur normally in human serum. The other antibody reacts with the same soluble antigen (RL) with which preimmune rabbit serum reacts. The agglutination spectra of different mouse serum samples were compared with spectra obtained with human and rabbit serum. There were some obvious similarities observed in the specificity of agglutinins for staphylococci from animals of different environments (germfree and conventional mice) and different species (mouse, human and rabbit). The source of or stimulus for the antibody formation has not been determined.