Table 4.

Mechanism of actions by which oat constituents modulate the immune system against infection.

Constituents	Actions
Fiber	Spare mucin (physical barrier against infection) from being utilized by the gut microbes Create an ecosystem unfavorable for survival of pathogens in the gut Substrate for production of SCFAs which promote gut integrity, exert anti-inflammatory action, regulate differentiation of naive T cells into Th1 and Th17 cells B-glucans enhance the responsiveness of the innate immune system
Copper, iron, selenium, zinc	Cofactors of antioxidant enzymes Protect immune cells from free radical attacks Regulate proliferation of immune cells
Polyphenols (e.g., ferulic acid, avenanthramides)	Regulate antioxidant defense system and innate and adaptive immunity via inhibition of NF-κB and AP-1 and activation of Nrf2 Display anti-inflammatory via increasing histone deacetylase activity, regulating transcription factors, and attenuating endoplasmic reticulum stress signaling Exert antiviral action suppressing neuraminidase and hemagglutinin activity, decreasing viral replication, hemagglutination, adhesion and penetration Increase IFNs, which contribute to inhibiting viral replication including SARS coronavirus via the activation of TLR-7 Promotes iron bioavailability in humans
Proteins	Substrate for proliferation and immune cells and molecules Regulates the proliferation of lymphocytes, neutrophils, and macrophages
Glutamine	Regulates proliferation of lymphocytes, neutrophils, and macrophages Required for the production of various cytokines, such as IL-6, IFN-γ, and TNF-α

Abbreviations: Th, T helper cells; SCFAs, short-chain fatty acids; TLR, toll-like receptor; SARS, severe acute respiratory syndrome; IFN, interferon; TNF, tumor necrosis factor; IL, interleukin.