Abstract
It is well known that nutritional status has profound effects on immunity. The compromised cellular immunity that occurs in many otherwise healthy older people includes impaired interleukin-2 (IL-2) production and anergy to skin test antigens. The latter has been associated prospectively with increased mortality in the elderly. We studied dietary and blood concentrations of vitamins A, B6, C and E, folate, β carotene, and zinc and their relationship to delayed hypersensitivity skin test responses (DHST) and serum soluble IL-2 receptor concentrations (IL-2R) in 65 healthy independently-living men and women aged 69.8 ± 7.2 years. Serum concentrations of vitamin B12 and copper and dietary lycopene were also measured. Excluded were subjects who had used vitamin or mineral supplements in the preceding 3 months, since supplementation may improve DHST responses. IL-2R concentrations were positively (p < 0.05) associated with serum concentrations of homocysteine, vitamin B6 and BMI, and negatively associated with serum β-carotene and dietary lycopene. In a multiple regression model, these 5 variables explained 52% of the variability in IL-2R. The percentage of subjects with anergy to a panel of 7 skin test antigens was 25%. DHST responses were negatively associated with T helper cell numbers and serum retinol, T helper cell numbers were positively associated with serum copper, and natural killer cell numbers were positively associated with dietary folate and vitamin B6. Serum homocysteine concentrations were negatively associated with plasma concentrations of folate, and vitamin B12, as well as positively with serum IL-2R. In a multiple regression model, these 3 concentrations explained 27% of the variability in serum homocysteine. The results suggest that IL-2 metabolism may be influenced by several dietary antioxidants and B vitamins including those that alter homocysteine concentrations.