Background: The precise mechanism of specific immunotherapy (SIT), long used for treating allergic diseases, remains undefined. SIT was shown to act by modifying the immune response of T lymphocytes to antigens. We examined the effect of SIT on the expression and use V‐alpha, ‐beta, ‐gamma and ‐delta chains of T‐cell receptors (TCR) in patients allergic to house‐dust mite.

Methods: Peripheral venous blood was taken for lymphocyte TCR analysis from 10 house‐dust mite (HDM) allergic adults before initiating SIT and 6 months after initiating the treatment. Twelve similarly allergic patients without SIT served as controls. TCR chains were identified by fluorescence‐activated cell sorter (FACS) using the following monoclonal antibodies: CD3, CD14, CD8, pan alpha‐beta, pan gamma‐delta, V‐alpha2, V‐alpha12.1, V‐beta5a, V‐beta5b, V‐beta5c, V‐beta8a, V‐beta8b, V‐beta3.1, V‐beta13, V‐beta12, V‐beta6.7, V‐delta1, V‐delta2, V‐gamma9, and V‐gamma4.

Results: Analyzed before and 6 months after SIT initiation, lymphocyte TCR showed significantly increased V‐beta5b, V‐beta12 and V‐alpha12.1 values compared to controls (without significant changes in other markers).

Conclusions: SIT caused selective expansion of certain V‐beta‐ and V‐alpha‐expressing T cells in patients allergic to HDM. Our results support the notion that the effect of SIT in patients with allergic rhinitis may be achieved by modifying the T lymphocyte response through the modulation of TCR usage.