Vulnerable Caregivers of Patients With Alzheimer's Disease Have a Deficit in Circulating CD62L- T Lymphocytes

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Abstract
The cell adhesion molecule, L-selectin (CD62L), serves a crucial role in the migration of naive T lymphocytes and is typically shed on cell activation. The objective of this study was to determine the effects of chronic stress on L-selectin expression on peripheral lymphocytes in elderly spousal caregivers of patients with Alzheimer's disease. Twenty caregivers (mean age, 73.5 years) had their lymphocytes and catecholamine levels sampled at rest and in response to an acute psychological stressor. Ten of the caregivers were classified as susceptible or "vulnerable" based on the large amount of care required by the patient relative to the amount of respite the caregiver received during the previous 6 months. At rest, vulnerable caregivers had 60% fewer L-selectin negative CD8 (+) T cells (CD8+ CD62L-) (p = .01) but no difference in CD8+ CD62L (+) cells. Vulnerable caregivers also showed significantly fewer CD4+ CD62L (-) T lymphocytes (p = .04) but no difference in CD4+ CD62L+ lymphocytes. Resting plasma epinephrine levels were 44% higher in vulnerable caregivers as compared with nonvulnerable caregivers (p = .01). The acute stressor increased circulating levels of CD8+ CD62L- and CD8+ CD62L+ lymphocytes and catecholamines similarly in both groups. The findings suggest that caregivers who are more vulnerable to the chronic stress of caregiving show a decrement in circulating CD62L- T lymphocytes, possibly by adrenomedullary activation. The data also suggest the identity of lymphocyte subsets that may underlie prior observations of immunologic decrements associated with the chronic stress of caregiving.