Functional properties of CD4+ CD28- T cells in the aging immune system

Mech Ageing Dev. 1998 May 15;102(2-3):131-47. doi: 10.1016/s0047-6374(97)00161-9.

Abstract

The aging immune system is characterized by a progressive decline in the responsiveness to exogenous antigens and tumors in combination with a paradoxical increase in autoimmunity. From a clinical viewpoint, deficiencies in antibody responses to exogenous antigens, such as vaccines, have a major impact and may reflect intrinsic B cell defects or altered performance of helper T cells. Here we describe that aging is associated with the emergence of an unusual CD4 T cell subset characterized by the loss of CD28 expression. CD28 is the major costimulatory molecule required to complement signaling through the antigen receptor for complete T cell activation. CD4+ CD28- T cells are long-lived, typically undergo clonal expansion in vivo, and react to autoantigens in vitro. Despite the deficiency of CD28, these unusual T cells remain functionally active and produce high concentrations of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2). The loss of CD28 expression is correlated with a lack of CD40 ligand expression rendering these CD4 T cells incapable of promoting B cell differentiation and immunoglobulin secretion. Aging-related accumulation of CD4+ CD28- T cells should result in an immune compartment skewed towards autoreactive responses and away from the generation of high-affinity B cell responses against exogenous antigens. We propose that the emergence of CD28-deficient CD4 T cells in the elderly can partially explain age-specific aberrations in immune responsiveness.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aging / immunology*
  • Arthritis, Rheumatoid / immunology
  • CD28 Antigens / immunology*
  • CD4-Positive T-Lymphocytes / immunology*
  • Cohort Studies
  • Cytokines / biosynthesis
  • Humans
  • Immune System
  • T-Lymphocytes, Helper-Inducer / immunology

Substances

  • CD28 Antigens
  • Cytokines