Does chronic caregiving stress accelerate T cell immunosenescence?

Abstract

First paragraph: It is now well understood that the human immune system undergoes considerable changes, termed immunosenescence, as part of the ageing process, resulting in an increased rate of infections and inflammation. The impact of stress is often studied in the context of such age-related changes, as detailed in this issue by Prather et al. (2018). In the innate immune system, immunosenescence changes include increased levels of inflammatory cytokines and markers such as CRP, accompanied by decreased anti-inflammatory cytokines; a skewing toward myeloid cell differentiation of haematopoietic stem cells; decreased phagocytosis, intracellular killing and dysregulated chemotaxis in neutrophils and macrophages/monocytes, increased NK and NKT cells but decreased cytotoxicity (Bosch et al., 2013). In the adaptive immune system, these alterations encompass decreased production of naïve T cells, especially cytotoxic CD8+ T cells, due to thymus involution and CMV exposure, decreases in T cell activation, reduced numbers of naïve B cells, and a switch towards accumulation of memory and effector T and B cells (Bosch et al., 2013). Chronic stress is known to exacerbate these changes further and affect a range of immune cells and immune processes such as slower wound healing and reduced antibody response to vaccination (Segerstrom and Miller, 2004).