EFFECTS OF MALNUTRITION - MALNUTRITION AND IMMUNE FUNCTION
Malnutrition is the most common cause of immunodeficiency in the world. Malnutrition and undernutrition clearly increase susceptibility to infection. Pneumonia and measles are among the most common acute infections in malnourished children and contribute to the deaths of many. Other infections are also more common among malnourished children. In one study, hepatitis B surface antigenemia was more common among Thai children with malnutrition than in well-nourished children (29% vs. 7.4%).
Many components of the immune system are affected by malnutrition. One of the most striking findings in malnutrition is a generalized increase in serum immunoglobulins, likely a response to increased antigen exposure (via chronic dermatitis, increased intestinal permeability, which enhances systemic absorption of food antigens and microbial toxins, and more frequent intestinal parasites). Undernutrition or malnutrition may impair responses to vaccines. Children with severe malnutrition may harbor severe infections without the usual clinical signs of infection.
Many of these changes in the immune system reverse with improved nutrition. However, improvement in immune function lags considerably behind nutritional rehabilitation. Recovery of some immune functions, especially cell-mediated immunity, may be incomplete. Ongoing micronutrient deficiency, chronic exposure to infectious diseases, or other environmental factors may impede complete restitution of the immune system. Thus, the malnourished international adoptee may be more susceptible to infection for some time even after nutritional rehabilitation is complete.