COX-2 up-regulation may also benefit the host defense against ExPEC XM O2:K1:H7 infection through down-regulation of the IL-10 expression, a known anti-inflammatory cytokine (Angus and van der Poll, 2013), and reduction of macrophage cell death during ExPEC XM O2:K1:H7 infection. Here, PTGS2 is linked to infection.