MPO and infection: Statistically significant higher iNOS mRNA levels in gp91phox−/− and MPO−/− Hoxb8 neutrophils compared to wild-type cells were not found upon infection (Fig. 3h), but at 24 h (U = 1, n1 = 4, n2 = 7, P = 0.0121) and 48 h (gp91phox−/− cells: U = 0, n1 = 4, n2 = 7, P = 0.0061; MPO−/− cells: U = 2, n1 = 4, n2 = 7, P = 0.0242) after LPS-stimulation (Fig. 3i).