DISSECTION OF THE GRASS ALLERGEN-SPECIFIC IMMUNE-RESPONSE IN PATIENTSWITH ALLERGIES AND CONTROL SUBJECTS - T-CELL PROLIFERATION IN PATIENTS DOES NOT CORRELATE WITH SPECIFIC SERUM IGE AND SKIN REACTIVITY

Background: Pollinosis, caused by grasses of the Poaceae family, is a problem worldwide. The relative importance of grass groups 1 and 5 maj or allergens is well established. However, not much is known about the recognition of these allergens by T cells and whether this T-cell rea ctivity correlates with skin reactivity and serum IgE levels. Objectiv es: The aim of this study was to characterize the cross-reactive, gras s allergen-specific T-cell responses from patients allergic to grass a nd nonatopic individuals and to investigate whether these responses co rrelate with grass-specific IgE and skin reactivity. Methods: Skin pri ck test wheal areas and grass-specific serum IgE levels were determine d in all patients (n = 21) and nonallergic control donors (n = 20). Pe ripheral blood mononuclear cells were isolated and stimulated with gra ss allergen extracts (Phleum pratense, Poa pratensis, Lolium perenne) and immunoaffinity-purified group 5 allergens, and the production of t ype 1 and type 2 cytokines was determined in the patient group. Result s: Donors allergic to grass showed increased T-cell-proliferative resp onses to grass allergens compared with nonatopic control subjects, We find it interesting that the magnitude of the patients' T-cell respons es could not be correlated with the individual skin prick test areas a nd specific serum IgE levels, and several patients with allergies to g rass had group 5-specific T-cell responses in the absence of group 5-s pecific IgE. The absence of a correlation between T-cell proliferation and IgE levels or skin prick test results may in part be explained by the finding that patients predominantly produced IL-5 in response to Phl p 5, the major allergen, and predominantly IFN-gamma in response t o Phl p extract. In general, all donors responded equally well to all three grasses. Additional experiments with Phl p 5-specific T-cell lin es indicated that the equal proliferation of peripheral blood mononucl ear cells to all three species is the direct result of cross-reactivit y. Conclusions: Grass allergen-specific T-cell responses are highly cr oss-reactive, and patients with allergies exhibit higher responses tha n nonallergic donors, suggesting that T cells are involved in the alle rgic reaction to grass group 5 allergens. However, group 5-specific T- cell responses are also found in donors without group 5-specific IgE, and the patients' grass-specific T-cell responses and cytokine product ion do not correlate to skin reactivity or to concentrations of grass- specific IgE.