T helper cell subset ratios in patients with severe sepsis.

T helper 1 (Thl) lymphocytes produce interferon gamma (IFNgamma), favouring cell mediated immunity; Th2 cells secrete interleukin-4 (IL-4), favouring humoral immunity. Cytokines produced in sepsis may effect Th subset predominance and subsequent immune responses. We measured Th subsets in ten patients with severe sepsis, seven APACHE II score-matched non-septic critically ill control patients, and ten healthy subjects. Mononuclear leukocytes were isolated and Th subsets identified by flow cytometry. The median (range) Th1/Th2 ratio was 0.46 (0.2-2.5) in patients with sepsis, which was significantly lower than both non-septic controls (median 2.5 (0.2-5.9), p = 0.050) and healthy subjects (median 3.9 (1.2-10.8), p = 0.01). In patients with sepsis, Th2 antibody mediated (humoral) immune responses predominate. This type of response may lead to fibroblast activation and ultimately immunosuppression. Modulation of Th cell subset predominance may present a novel therapeutic option in the treatment of severe sepsis.