Interleukin-5 production by mononuclear cells from aged individuals: implication for autoimmunity

It is well known that in the elderly a deterioration of immune functions ma y occur. Particularly, stimulation of T cells from aged individuals leads t o different kind and/or size of responses if compared with the responses ob tained from T cells from young individuals. At the same time, an increase i n prevalence of autoantibodies occurs in elderly. The altered production of certain cytokines might explain this paradox of decreased responsiveness t o foreign antigens in the face of an increased response to self-antigens. W e and others have suggested that this kind of immune response might depend on an age-associated impairment of Th-1 type function that selectively affe cts production of cytokines involved in the control of cellular responses. In contrast, Th-2 type function is seemingly not affected in elderly, as su ggested by normal in vitro production of cytokines involved in humoral resp onses. To strengthen this hypothesis, in this study we have analysed the in fluence of age on the ability of mitogen-stimulated cultures of peripheral blood mononuclear cells from human beings to produce another Th-2 type cyto kine, i.e. interleukin-5 (IL-5). IL-5 content of both 24- and 48-h stimulat ed cultures from old individuals was greater than that of young ones, altho ugh this difference attained significance only at 48 h. We suggest that the decreased production of Th-1 type cytokines in the presence of a normal or even increased production of Th-2 type cytokines might account for the pat tern of immune response which may be observed in elderly, i.e. a normal or increased humoral response, including an autoimmune one, in the face of a l ow cell mediated immune response. (C) 1999 Elsevier Science Ireland Ltd. Al l rights reserved.