Immunological factors in nutritional assessment

Multiple studies have demonstrated that malnutrition is one of the major causes of increased morbidity and mortality among hospitalized patients.A variety of anthropometric, biochemical and immunological parameters has been used as indicators of protein-energy malnutrition.However, the relative value of each of these measurements has not been clearly defined.This is especially true for the immunological parameters, where abnormalities are often observed in clinical and subclinical malnutrition.The purpose of this,paper is to review and discuss some of the most significant results relating to (I) the effects of malnutrition on the immune processes and (2) the effectiveness of immunological testing and assessment of nutritional status to identify high-risk patients. Effects of malnutrition on the lymphoid organsIn malnutrition the primary lymphatic structures of the immune system, notably the thymus, as well as such secondary structures as the spleen and lymph nodes, are significantly altered in size, weight, architecture and cellular components.The thymic-dependent areas are especially affected.Germinal centres are usually reduced in number, but occasionally are normal or even increased.There is poor documentation of the structural alterations in the gut-associated lymphoid tissues in malnutrition.The tonsils and adenoids are often small to the point of being vestigial.In our laboratories, lymphoid tissues of six malnourished dogs were histologically evaluated and compared to the same lymphoid structures of dogs nutritionally repleted by means of total parented nutrition (TPN).The results showed that thymus, spleen, lymph nodes and Peyer's patches were markedly atrophic and severely cell depleted in malnourished dogs, and provided evidence that subsequent TPN therapy stimulates and supports lymphoid cell proliferation, leading to cell repopulation of previously depleted lymphoid structures (Table I) (Dominioni et al. 1976). Effects of malnutrition on phagocytic activityAs early as 1946, it was shown that protein-energy malnutrition in rats inhibited the phagocytosis and killing of bacteria by peritoneal cells (Guggenheim & Buechler, 1946).Many recent studies have investigated the production, mobilization and other aspects of phagocytic function in malnutrition.The total leucocyte count in nutritional deficiency is usually increased or normal.Acute sepsis in malnourished patients can reduce the number of total white cells, https://doi.org/10.1079/PNS19820051Published online by