Health Questions and Answers

Question: What is the effect of calorie or protein-calorie malnutrition (PCM) on the immune system?


Calorie malnutrition by itself is relatively rare and is usually combined with protein malnutrition to produce PCM, also known as protein-energy malnutrition (PEM). PCM impairs host immunity with particular detrimental effects on the T-cell system, resulting in increased opportunistic infection and increased morbidity and mortality in malnourished hospitalized patients. Phagocytosis and bacterial killing are significantly impaired in PCM. The local immune system of children suffering PCM has been shown to be deficient in IgA. Delayed hypersensitivity reactions, which are mediated by T-cells, are often suppressed. The defective T-cell mediated response may predispose the individual to such diseases as tuberculosis.

Despite these specific defects, the immune system is resistant to malnutrition. Both adults and children suffering from PCM are still capable of antibody responses and can mount both lymphocyte response and leukocytosis. In animal studies the gut immune system is preserved despite significant protein calorie malnutrition. Putting it another way, immunity is maintained at the expense of other tissues. Muscles serves as a reservoir of energy and amino acids which can be drawn upon in illness or injury. Malnourished individuals will show muscle wasting long before the immune system fails.

Protein-calorie malnutrition has somewhat similar effects to AIDS. The specific defect produced by AIDS is depletion of T-helper cells (CD4 cells) and depression of the T-cell-mediated immune response. Infections which are thereby facilitated include Pneumocystis carinii pneumonia, herpes, and tuberculosis. The similarity between PCM and AIDS suggest a synergy between the two conditions. Indeed, this can be seen in Africa, where AIDS is known as the “slim disease” because of its link with malnutrition. Prevention and treatment of PCM is animportant part of the management of the patient with AIDS.

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