Ageing is associated with a progressive decline of immune responsivene
ss to exogenous antigens and increasing incidence of autoimmune phenom
ena [1,2]. Many studies have been focused on the mechanisms of the imm
unologic features of ageing. Alterations in cellular components of the
immune system rather than in the extracellular milieu seem to account
for most of the variations of immune competence in ageing [3].