THE DERMATOPHAGOIDES-PTERONYSSINUS NATIVE MAJOR ANTIGEN DER PII ACTS AS POLYCLONAL ACTIVATOR

It has long been debated whether or not house dust mite products exert non-antigen specific mitogen activity. The aim of this study was to s tandardise in normal subjects the lymphocyte proliferation assay by me ans of the identification and stabilisation of all possible confoundin g variables, and to use this method to investigate the immunogenic and mitogenic properties of Der pI and Der pII, the native major antigens of the house dust mite Dermatophagoides pteronyssinus, in normal subj ects. Der pI was not immunogenic in any normal subject tested; in fact , no significant differences were found between Der pI-stimulated cult ures and the spontaneous proliferation values of the unstimulated cont rol cultures. On the contrary, Der pII exerted mitogenic activity at c oncentrations of 5 mu g/ml and 10 mu g/ml (p 0.007 and 0.000, respecti vely). The dose-response curves of Der pII and Phaseulus vulgaris lect in show overlapping trends, i.e., the proliferation increased steadily in both assays with increasing antigen dose. The lack of significant inhibition of Der pII-induced cellular responses, after a block perfor med with a monoclonal antibody capable of recognizing a non-polymorphi c determinant shared by major histocompatibility complex (MHC) class-I I products DR, DP and DQ, suggests that class-II MHC restriction is no t required in normal subjects, thus confirming the polyclonal activato r nature of the investigated purified Der pII antigen.