Initial events and T cell activation in lymphokine-mediated allergic responses in patients with hen egg allergy

Specific induction of IL2-responsiveness by ovalbumin-stimulated lymphocytes was studied in patients with hen egg allergy. Fluorescence-activated cell sorter analysis of the cells showed that the IL2-absorbing and IL2-responding cells mainly consisted of CD3+2+4+8-45RA+ cells that may act as helper cells for IgE production and/or as effector cells for delayed type hypersensitivity. beta-Chains (P75) of IL2 receptors were involved in ovalbumin-induced IL2 responsiveness of the patients' lymphocytes, whereas the alpha-chains (p55) were expressed on normal lymphocytes stimulated with ovalbumin as well. Adhering mononuclear cells from patients allergic to ovalbumin but not to Dermatophagoides farinae (Df) were pulsed with ovalbumin antigen then added to a T cell-rich population. After five days of culture, we evaluated cell growth for IL-2 sensitivity during an additional 3-day culture in the presence of IL-2. Responder cells from the patients, which were cocultured with ovalbumin-pulsed autologous adhering cells, acquired IL2 responsiveness; whereas, those cultured with Df-pulsed adhering cells did not. This reaction was specific for antigen. The monoclonal antibody to HLA-DQ (Leu 10) and HLA-DP (HLA-DP) frameworks, but not the one to the HLA-DR framework (OKIa1), blocked the antigen presenting cells ability to induce responses. T Cell-rich responder cells depleted of CD4+ cells did not acquire IL2-responsiveness, whereas the depletion of CD8+ cells had no effect. As a whole, the results indicate that DQ-bearing and/or DP-bearing adhering cells have a key function in presenting ovalbumin-antigen to allergen-specific responder T cells that very likely belong to CD4+ subsets.