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Sublingual immunotherapy has been recognized as an alternative to injected immunotherapy for the treatment of allergic diseases. Even if compelling clinical evidence supports such a view, few studies are available on its mechanisms of action. This study was carried out to investigate the peripheral lymphocyte Vbeta repertoire of subjects with mite-allergic respiratory allergy who were either not treated or treated for 2 years with mite-specific sublingual immunotherapy. The T-cell receptor Vbeta distribution was studied by flow-cytometric techniques in three subject groups. Group A (untreated) included 19 subjects with symptomatic, mite-allergic, low to moderate asthma and/or rhinitis. Group B (treated) was made up of 10 asymptomatic subjects treated for 2 years with mite-specific sublingual-swallow immunotherapy for low to moderate asthma and/or rhinitis. Group C (controls) included 10 healthy subjects. The Vbeta usage was investigated with monoclonal antibodies specific to the diverse beta segments V3, V5a, V5b, V5c, V6a, V8a, V8b and V12a. The comparison between the group A and group C repertoires showed a lower expression (p < 0.05) of the beta V8b+ T-cell subset. The group B repertoire, when compared with group A, showed a significantly greater usage of the beta V5a (p <0.05), 8a (p <0.05) and 12a (p <0.01) segments. The significantly lower expression of beta V8b observed in the symptomatic untreated group was not present in the group that was asymptomatic after treatment. The oligoclonal expansion observed in the treated group was consistent with the development of suppressor T-cell and/or of Th1 clones but not with deletion mechanisms of induced tolerance.

We investigated by enzyme linked immunoassay( ELISA )the IgE response to whole extract of the housedust mite Dermatophagoides pteronyssinus (Dp) and to the native major allergens, Der p 1 and Der p 2, in sera from 18 adult patients (group A) with Dp-allergic asthma before (t0) and 1,2,3 and 4 t1-t4) years after subcutaneous specific immunotherapy (SIT). A qualitative reduction (P=0.05) of the IgE responses to Dp and Der p 2 was observed from t1 to t4, but a highly statistical significant decrease at t3 (P<0.01). With regard to Der p 1 IgE values, the immunotherapy induced a significant decrease (P<0.01) at t3, but not before. In group A, the IgE responses to Der p 1 and Der p 2 were not correlated at t0 (rs = 0.31; P = 0.21) but were correlated at t3 (rs=0.78; P0.001). We also examined sera from 14 adult patients (group B, same SIT schedule as group A) who were without respiratory symptoms at the end of the third year (t3) of Dp SIT. At this time (t3), there were no significant differences in Der p 1 and Der p 2 IgE levels between group A and group B. [ABSTRACT FROM AUTHOR]