TAC1 and infection: In a study by Verdrengh et al., Staphylococcus aureus was administered intravenously to neurokinin-1 receptor (NK-1R) knockout mice (without receptors to substance P) and control mice, and found that NK-1R knockout mice compared to control mice showed fewer phagocytose bacteria capacity of macrophages, higher burden of staphylococci in the kidneys, more severe arthritic lesions with more severe synovitis and cartilage/bone destruction, and higher 11-day post-infection mortality rate [19].