Allergen-specific production of interferon-gamma by peripheral blood mononuclear cells and CD8 T cells in allergic disease and following immunotherapy

Background CD8 T cells are important immunoregulatory cells in animal model s of allergic disease, but their role in human allergic immune responses ha s not been defined. With the development of novel immunotherapeutic reagent s, it is clearly important to ascertain whether CD8 T-cell responses are al tered following conventional allergen-specific immunotherapy (SIT) and henc e targets for future developments/strategies. Objective To study the allergen-specific cytokine release of freshly isolat ed CD8 T cells from the blood of separate groups of house dust mite- (HDM) allergic patients, patients post-SIT and control nonatopic donors. Methods CD8 T cells were isolated by positive selection with immunomagnetic beads and cultured with the affinity purified major mite allergen Der p 1 or with different mitogens, using irradiated autologous peripheral blood mo nonuclear cells as antigen-presenting cells (APCs). Supernatants were colle cted at a number of time points and assayed by ELISA for the cytokines inte rleukin (IL) -4, IL-5 and interferon-gamma (IFN gamma). Results CD8 T cells stimulated with Der p 1 produced significant quantities of IFN gamma with cells from HDM-allergic subjects releasing considerably more IFN gamma than cells from nonatopic subjects, an average of 804 +/- 28 3 pg/mL of supernatant compared with 30.2 +/- 18.8 pg/mL (P = 0.006). The c ytokine was detected in cultures of 16/17 of the allergic subjects and 4/7 of the nonatopic. CD8 T cells from 6/10 patients who had received HDM-SIT r eleased IFN gamma at an average of 363 +/- 202 pg/mL, which was less than t he allergic group but still higher than the nonatopic (P = 0.05). Equivalen t levels of IFN gamma were detected when the cells were stimulated with the mitogen PHA and this was the same in all groups. Reliable allergen-specifi c release of significant quantities of IL-4 or IL-5 was not detected from C D8 T cells. Conclusion Allergen-specific IFN gamma is produced at far greater levels fr om CD8 T cells of HDM-sensitive allergic patients than from nonatopic contr ol individuals and this level is reduced following SIT.