NOS2 and infection: Exogenous riboflavin directly controls infection in three ways: 1) it inhibits transcription of bacterial LPS (Figure 2b); 2) it reduces the level of NO or expression of iNOS; and 3) it regulates the functions of innate immune cells (such as macrophages and neutrophils) and the levels of immunoreactive materials, including TNF, ILs, and IFN.