The age-associated decline in immune function of healthy individuals is not related to changes in plasma concentrations of beta-carotene, retinol, alpha-tocopherol or zinc.

The decline in the lymphoproliferative response to mitogenic stimuli shows marked heterogeneity in elderly individuals. Adequate nutriture is required for optimal immune function, yet nutritional status may be compromised in the elderly. To address whether this variation in the proliferative response of elderly individuals is related to their nutritional status, we studied 61 elderly (80.5 +/- 5.7 year-old) and 27 young (27.3 +/- 3.8 year-old) individuals participating in an ongoing assessment of their immune response to influenza vaccine. Ambulatory elderly individuals were recruited from five different retirement communities and were in good health upon enrollment in the study. Thirty-three percent of young and 54% of elderly subjects reported consuming micronutrient supplements daily during the study. Plasma and peripheral blood mononuclear cells (PBMC) were isolated from fasting individuals twice, 4-6 weeks apart. At both times, proliferative responses to the mitogens phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM) were significantly lower (P < 0.004) in the elderly compared to the young. However, at both times, elderly participants had plasma concentrations of beta-carotene, retinol, alpha-tocopherol and zinc that were either significantly greater than, or equal to, those of young subjects. No significant correlations between plasma concentrations of beta-carotene, retinol, alpha-tocopherol and zinc and level of proliferative responses to each stimuli were observed in elderly individuals at either time. Thus, the heterogeneity in the proliferative response to mitogenic stimuli exhibited by a healthy elderly population cannot be attributed to differences in these nutritional parameters.