CCR5 and bacterial infectious disease: On the other hand, RAT of CCR5 and other CC and CXC families of chemokine receptors containing a GXXXN motif in their first transmembrane helix may explain why macrophages overwhelmed by LPS during sepsis are markedly less effective in clearing bacterial infection, as they may be less sensitive to chemotaxis reaction (Biswas and Lopez-Collazo, 2009).