a switch from T helper 1 (TH1) to T helper 2 (TH2)-like cytokine production has been proposed for progressive HIV infection.

to study whether this hypothesis is reflected by altered IL-12 and IFN-γ serum levels in HIV patients.

we measured serum levels of IL-12 p40 and p70 and IFN-γ in 90 HIV seropositive patients at differing disease stages and in 10 healthy controls by radioimmunoassays. These cytokines were compared to established surrogate markers of immunodeficiency.

IFN-γ, as well as IL-12 p40 and p70, levels were significantly increased in HIV patients compared to controls. However, IFN-γ and IL-12 showed on significant variations with progressive stages of immunodeficiency. IFN-γ levels showed a significant positive correlation to the progression marker β₂-microglobulin and correlated negatively with CD4⁺ lymphocyte counts. In addition, IFN-γ concentrations were related to sTNF-R p55 and p75 serum levels. Interestingly, IFN-γ was related to IL-12 only with respect to p40, but not to p70.

although our data do not necessarily reflect cytokine secretion at the single cell level or the cytokine milieu in the lymphoid microenvironment, our results from peripheral blood fail to demonstrate progressively decreased IL-12 and IFN-γ serum levels in HIV infected patients.