The differentiated THP-1 cells secreted IL-8 in response to infection by Δslo, Δnga, and NgaR289K/G330D mutants but not JRS4 wild-type or Δnga::nga strains (Fig. 6B), which suggests that SLO and Nga may inhibit IL-8 secretion by macrophages. Here, CXCL8 is linked to infection.