Evidence for a shift in the Th-1 to Th-2 cytokine response associated with chronic stress and aging

Background. A number of studies have shown that the chronic stress of caring for persons with dementia can have significant immunological consequences as demonstrated by the down-regulation/dysregulation of the cellular immune response. Methods. Utilizing flow cytometry to measure the percentages and absolute numbers of CD-4(+) and CD-8(+) T lymphocytes producing the cytokines indicative of Th-1, Tc1 and Th-2, and Tc2 cells, we compared spousal caregivers and control subjects. The expression of interleukin-2 (IL-2), interferon gamma (IFN-gamma), and interleukin-10 (IL-10) in the cytoplasm of CD-4(+) and CD-8(+) lymphocytes was assessed. Results. Neither stress nor age was significantly related to the percentage or number of IFN-gamma (+)/CD-8(+), IL-2(+)/CD-8(+) cells, or IFN gamma (+), IL-2(+), CD-4+ cells. However, the percentage of IL-10(+) cells was higher in lymphocytes obtained from caregivers than control subjects. In addition, the significant interaction between stress and aging for IL-10(+)/CD-4(+) and IL-10(+)/CD-8(+) cells demonstrated that the difference between caregivers and control subjects was age dependent; the difference between caregivers and control subjects was substantially larger in younger individuals than in older individuals. Conclusions. The data are consistent with previous reports on acute stress and suggest that there may also be a shift from a Th-1 to a Th-2 response associated with a chronic stressor such as caregiving. This shift could have implications for an individual's responses to pathogens.