Specific and nonspecific immune responses to fasting and refeeding differ in healthy young adult and elderly persons

Background: Undernutrition is a main cause of immunodeficiency. Many confou nding factors limit the interpretation of immune function in hospitalized e lderly patients. Objective: We compared the effects of short-term fasting and refeeding on l ymphocyte subset distribution and neutrophil function in healthy subjects. Design: Seven young adult ((X) over bar +/- SE age: 24 +/- 2 y) and 8 elder ly (71 +/- 3 y) subjects were fed standardized diets (1.6 X predicted resti ng energy expenditure; 16% protein) for 7 d. They then fasted for 36 h and were refed for 4 h (42 kJ/kg). Lymphocyte subsets were quantified by using fluorochrome-conjugated monoclonal antibodies. Neutrophil chemotactic migra tion was evaluated by using a 2-compartment chamber. Neutrophil reactive ox ygen species production was measured by using a luminol-amplified chemilumi nescence assay and oxidation of 2'7'-dichlorofluorescein diacetate. Results: Baseline total and cytotoxic T lymphocyte subpopulations were lowe r in elderly than in adult subjects (P < 0.01). Nutritional state had a sig nificant effect (P < 0.05) on total, helper, and cytotoxic T and B lymphocy te counts in all subjects, and the response of lymphocyte subpopulations to nutritional fluctuations was significantly affected by age. The chemotacti c index was lowered by fasting in both groups (P < 0.05 compared with basal values). After refeeding, neutrophil migration was restored in adult but n ot elderly subjects. The superoxide anion production rate increased with fa sting and reverted to prefasting values with refeeding in both groups (P < 0.05). Fasting induced a significant decrease in hydrogen peroxide producti on in stimulated neutrophils that was reversed by refeeding in adult but no t elderly subjects. Conclusion: The lack of response of lymphocyte subpopulation counts and neu trophil function to nutritional changes may help to explain the proneness o f elderly persons to infection.