KEYNOTE SPEECH

Malnutrition, Immune Function, and Infection

Prof . R. Nassiri

Department of Clinical Pharmacology, LECOM, Erie, PA,USA

It has long been recognized that malnourished Indivduals are at higher risk for infectious diseases due to an inadequate immune response. Malnutrition and immunodeficiences often increase the frequency and severity of infectious diseases, especially in infants and children . A wide variety of pathogenic microorganisms, including viruses, bacteria, rickettsiae, spirochetes, and parasites, can invade the immune host to initiate infection.

Symptomatic infectious illnesses as well as asymptomatic ones are accompanied by direct or functional losses in the body content of many nutrients and by redistribution in the body localization of others. If infectious process is not elminated and becomes subacute, chronic, or progressive, body composition becomes significantly altered, which would lead to formation of a new equilibrium, however, a cachectic, severely wasted level. As inadequate immune response is common in malnourished individuals, the likelihood of infection in these patients group will lead to inflammatory responses and worsening nutritional status. Which in turn, further compromises the immune system. Such outcome is termed vicious cycle, which is common in AIDS and tuberculosis. Numerous studies have shown decreased function of the organs such as thymus, spleen, and lymph nodes of the immune system in malnourished humans. Further, the humoral arm of the immune system, which produces antibodies, is depressed in malnutrition in particular. Malnourished individuals show decreased CD4+ and CD8+ T-cell counts, and such cells have less ability to amplify or respond to infectious organisms . In addition, the functions of cytokines (eg.IL-2), chemicals that act as cell messengers, are also altered in malnourished individuals. From the standpoint of inadequate protein intake and cell mediated immunity, generalized protein-energy malnutrition (PEM) causes marked repression of cell-mediated immunity at large and T-lymphocytes.

Often, malnourished children show dermal anergy, with the loss of delayed dermal hypersensitivity ( DDH) reactions, a decrease or reversal of the T helper/suppressor cell ratio, and loss of the ability of killer lymphocytes to recognize and destroy foreign entities . On a different level of the assessment of malnutrition and immunodeficiency, lack of a large number of single essential nutrients can also produce dysfunction in the immune system and to other host defensive mechanisms. Clinically, the most important of the single nutrients deficiencies in terms of their immunological effects in malnourished children, are the vitamins A and the trace metals, iron, zinc and selenium. When considering the immunological role in host defensive mechanisms, it is often helpful to categorize the essential nutrients according to what they do. As for amino acids, arginine deficiency plays a central role in immunodeficiency . A deficiency of arginine can diminish the production of nitric oxide, and conversely , arginine supplementation may lelp strengthen host defense . And antioxidant deficiencies can allow increases in the damaging effects of free oxygen radicals. Finally, nutritionally acquired immune deficiency syndrome (NAIDS) is also associated with malnutrition and immunological dysfunction.NAIDS is seen most frequently in children throughout the world, it is often seen in elderly individuals, and it is an all too common complication of several medical or surgical diseases, burns and other forms of trauma being treated in most modern hospital settings. It should be noted that combination of NAIDS and common childhood infections is the leading cause of human mortality, producing more than ten million childhood deaths annually.

In conclusion, the countless and intricate relationships between nutritional status, specific nutrients, and the immune system are an exciting and ongoing area of medicine in 21 century . Malnourished individuals are at risk of immune dysfunction, which may lead to infectious diseases. Several micronutrients have significant roles in the functions of the immune system, including iron, zinc, and selenium. Finally, aggressive nutritional support in people with HIV disease may delay the develoment of NAIDS