title: Age-related differences in polyfunctional T cell responses.
abstract: BACKGROUND
  A reduced number of naïve T cells along with an accumulation of differentiated cell types in aging have been described but little is known about the polyfunctionality of the T cell responses. In this study we compared the individual and polyfunctional expression of IFN-γ, MIP-1α, TNF-α, perforin, and IL-2 by T cell subsets, including the newly described stem cell like memory T cells (TSCM), in response to stimulation with superantigen staphylococcal enterotoxin B (SEB) in older (median age 80, n = 23) versus younger (median age 27; n = 23) adults.
  
  
  RESULTS
  Older age was associated with a markedly lower frequency of CD8+ naïve T cells (11% vs. 47%; p < 0.0001) and an expansion in memory T cell subsets including central memory (p < 0.05), effector memory and effector T cells (p < 0.001 for both). There was also a decline in CD4+ naïve T cells in older subjects (33% vs. 45%; p = 0.02). There were no differences in frequencies or polyfunctional profiles of TSCM between groups. CD8+ naïve cells in the older group had increased expression of all functional parameters measured compared to the younger subjects and exhibited greater polyfunctionality (p = 0.04). CD4+ naïve T cells in the older group also showed greater polyfunctionality with a TNF-α and IL-2 predominance (p = 0.005). CD8+ effector memory and effector T cells exhibited increased polyfunctionality in the older group compared with younger (p = 0.01 and p = 0.003).
  
  
  CONCLUSIONS
  These data suggest that aging does not have a negative effect on polyfunctionality and therefore this is likely not a major contributor to the immunesenescence described with aging.
authors.affiliation: Geriatric Research Center Clinical Core (GRECC), Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, Cleveland, Ohio 44106, USA ; Division of Infectious Diseases, Case Western Reserve University School of Medicine, 10900 Euclid Ave, BRB 1022, Cleveland, Ohio, 44106-4684, USA.
authors.forename: Puja
authors.initials: P
authors.lastname: Van Epps
authors.affiliation: Geriatric Research Center Clinical Core (GRECC), Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, Cleveland, Ohio 44106, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Banks
authors.affiliation: Geriatric Research Center Clinical Core (GRECC), Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, Cleveland, Ohio 44106, USA ; Division of Infectious Diseases, Case Western Reserve University School of Medicine, 10900 Euclid Ave, BRB 1022, Cleveland, Ohio, 44106-4684, USA.
authors.forename: Htin
authors.initials: H
authors.lastname: Aung
authors.affiliation: Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Betts
authors.affiliation: Geriatric Research Center Clinical Core (GRECC), Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, Cleveland, Ohio 44106, USA ; Division of Infectious Diseases, Case Western Reserve University School of Medicine, 10900 Euclid Ave, BRB 1022, Cleveland, Ohio, 44106-4684, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Canaday
keywords: Aging; Immunesenescence; Polyfunctionality; T cells