Ageing, autoantigen specific-Ts cells, involution of the thymus, autoimmunity and autoimmune diseases

An age-related gamma delta T cell suppressor activity correlates with the outcome of autoimmunity in experimental Trypanosoma cruzi infection

In this work the suppressive activity of splenic T cells from young and aged BALB/c mice infected with Trypanosoma cruzi were compared and correlated with the development of autoimmune myocarditis. The T cells from young adult BALB/c mice with acute T. cruzi infection exhibit suppressor activity when added to full allogeneic or Mls-disparate mixed lymphocyte cultures. This suppression could not be reverted by exogenous interleukin (IL)-2 and was not directly dependent on the presence of IL-4, IL-10 or transforming growth factor-beta. Further characterization of the T cell lineage responsible for the suppressor activity by in vitro and/or in vivo depletion with monoclonal antibody to alpha beta or gamma delta T cell receptor revealed that splenic gamma delta T cells function as suppressor lymphocytes in young T. cruzi-infected mice. In addition, these young adult BALB/c mice do not develop autoimmune myocarditis and showed a low incidence of syngeneic heart graft rejection in the early chronic phase of the infection. In contrast, T cells from acutely infected aged BALB/c mice lacked demonstrable T suppressor activity. Furthermore, these mice developed a severe autoimmune myocarditis as early as 2 months after the onset of the infection, when the majority of them reject syngeneic heart grafts. These findings suggest that a gamma delta T cell-mediated suppressor mechanism may operate in the avoidance of the breaking of tissue-specific tolerance during the acute infection. Moreover, such a mechanism is likely related to the immune system chronobiology.