Comparison of T–Cell Responses Induced by Major and Less Major Allergens of the House Dust Mite

The importance of the allergens has been based on IgE–binding characteristics. The group 1–3 house dust mite allergens bind IgE in 80% of sera from allergic subjects while the other allergens Der p 5 and 7 bind in 40–50% sera, but at the same intensity as the major allergens [1]. Der p 7 has been studied here as an example of a less major allergen, a designation used because it still sensitizes a very large number of people. Our aim was to compare the T–cell responses to the group 1 and 7 allergens from Dermatophagoides pteronyssinus and D. farinae. Microtiter tray cultures of peripheral blood mononuclear cells (PBMC) in AIM V serum–free medium were stimulated with affinity–purified Der p 1, Der p 7, Der f 1 and Der f 7. Proliferation was measured by 3H–thymidine incorporation and IL–5 and IFN–γ in day 4 and 6 supernatants. IL–5 was assayed by the proliferation of BAF3 mouse cells transfected with huIL–5 R and IFN–γ by ELISA. IL–4 was <5 pg/ml and could not be reliable detected. Der p 1 and 7 induced equally strong proliferative responses in all allergic and non–allergic subjects (table 1). The release of IL–5 by PBMC from all allergic subjects was the same after Der p 1 and 7 stimulation. Little IL–5 was produced by PBMC of non–allergic subjects. IFN–γ was variable but PBMCs from non–allergic subjects tended to produce higher levels to both allergens. The responses to Der f 1 and 7 were essentially the same as the responses to Der p 1 and 7.(1) Der p 7 induced the same T–cell proliferation and IL–5 release as Der p 1 in all allergic subjects despite the fact that it only binds IgE in 50% of sera. Subjects without IgE to Der p 7 are therefore not non–responders and the allergen can induce allergic inflammation via the release of cytokines. This unexpected result has been corroborated by studies with recombinant Der p 7 in house–dust–mite–allergic individuals shown to lack IgE reactivity to Der p 7.(2) The equal responses induced by D. pteronyssinus and D. farinae allergens were notable because the study environment of Perth is almost devoid of D. farinae. Previously we found the same group reacted to 19–mer peptides of Der p 1 but poorly to Der f 1 peptides [2]. The difference may lie in the efficacy of the synthetic and natural peptides or in cross–reactive polymorphisms.