L-glutamine has demonstrated immunomodulatory activity in animal models of infection and trauma, as well as trauma in humans. L-glutamine acts as the preferred respiratory fuel for lymphocytes, is essential for cell proliferation, and can enhance the function of stimulated immune cells.
Extracellular glutamine concentration affects lymphocyte, IL-2 and IFN-gamma proliferation, cytokine production, phagocytic and secretory macrophage activities and neutrophil bacterial killing (Miller 1999, Newsholme 2001, PDRHealth 2006a). In humans, L-GIn may enhance both phagocytosis and reactive oxygen intermediate production by neutrophils (Furukawa et al 2000) and support the restoration of type-1 T-lymphocyte responsiveness following trauma (Boelens et al 2004). In a randomised trial there was a reduced frequency of pneumonia, sepsis and bacteraemia in
patients with multiple trauma who received glutamine-supplemented enteral nutrition (Houdijk et al 1998).
In addition, effects on the gastrointestinal tract may contribute significantly to immune defence by maintaining gut-associated lymphoid tissue and secretory IgA (preventing the attachment of bacteria to the gut mucosa) and maintaining gut integrity (thus preventing the translocation of microbes and their toxins, especially Gram-negative bacteria from the large intestine) (Miller 1999, Yu et al 1996).
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