Studies by Nilsson and colleagues [41] showed that mice inoculated with the Sar A+ staphylococcal strain exhibited a more pronounced T- and B-lymphocyte activation and higher levels of serum IL-6 and IFN-γ, compared with a Sar A-/- mutant, and infection with Sar A+ staphylococci induced pronounced weight loss as well. This evidence concerns the gene IL6 and infection.