Staphylococcal protein A (SpA): a potent in vivo chemotactic agent for rat leucocytes

Staphylococcal protein A had strong chemotactic attraction in vivo to rat leucocytes. Doses as small as 5 micrograms attracted net leucocytes into experimental pellets in 6 h. 50 micrograms Staphylococcal protein A showed maximum chemotactic activity and does greater or less than 50 micrograms attracted less net leucocytes into experimental pellets. The effect of time on the chemoattraction of 50 micrograms Staphylococcal protein A showed that it was an early chemoattractant. Chemotactic activity for this dose, shown by the chemotactic index, reached a peak at 6 h followed by maximum leucocytic infiltration, and almost disappeared completely at 12 h. Leucocytic migration into control pellets rose from 3 h and reached a peak at 12 h (later than the chemotactic peak). Staphylococcal protein A also showed in this study a "later reaction" from 24 to 36 h, resulting in local inflammation of the test site and rise in cellular response.