Effect of prolonged modified fasting in obese persons on in vitro markers of immunity: lymphocyte function and serum effects on normal neutrophils.

The effects of nutritional manipulation on immune function have been extensively studied in animals, but few studies have examined dietary restriction in humans. Obese patients enrolled in a protein-sparing, calorically restricted diet were monitored over a 3-month period with in vitro examination of mitogen- and antigen-induced lymphocyte blastogenesis. The sera from these patients were evaluated for effects on neutrophil chemotaxis, phagocytosis and microbial killing. Significant changes in body weight, triglycerides and glucose occurred during the diet, and most patients exhibited urinary ketosis. The diet was associated with increased blastogenesis in unstimulated cultures and in varicella and candida antigen-stimulated cultures, but blastogenesis was unchanged for phytohemagglutinin, concanavalin A, SK-SD and histoplasma. In assays of serum effects on neutrophil function, patients with urinary ketosis had depression of chemotaxis and microbial killing but not phagocytosis when compared to baseline or nonketotic patients. This study indicates that long-term caloric restriction is associated with significant effects on in vitro lymphocyte stimulation and with significant serum effects on normal neutrophil function.