Inflammatory reactions to staphylococcal protein A in mice

To throw more light on the role of Protein A (a cell-wall component of most strains of S. aureus), in infection and inflammation, due to this organism the immediate inflammatory reaction has been studied in hairless and hairless/obese mice after s.c. injection of the protein into the footpad following various forms of immunization or pretreatment (described). Non-immunized mice showed an inflammatory reaction to Protein A, as judged by swelling, reaching a peak 2 h after injection. This might have been due to a nonspecific interaction between certain mouse Igs and Protein A. When specific antibody levels were raised by prior immunization or infection, the swelling was greatly increased. No delayed reaction was seen at 24 or 48 h, nor was a positive patch test obtained. The difference in results seen in mice and other animals may be due partly to the fact that intradermal injections are not possible in the mouse, or because in the mouse, unlike other subjects which have been used, histamine does not play a part. Mice do not show anaphylactic shock and this may be a function of the class of murine Igs interacting with Protein A. Further studies on these factors are required.