Analysis of the T cell receptor Vγ region gene repertoire in bronchoalveolar lavage (BAL) and peripheral blood of atopic asthmatics and healthy subjects

Abstract

We analysed the T cell receptor (TCR) Vγ repertoire in BAL and peripheral blood (PBL) of three mild stable atopic asthmatics and two non-asthmatic controls. We used the polymerase chain reaction (PCR) to establish the expression of the four Vγ families, and to detect oligo or monoclonal expansion of γδ⁺ T cells, we resolved the PCR products on denaturing and non-denaturing gels to find the extent of junctional diversity arising from differences in the lengths of the V(D)J junctions. We also subcloned and sequenced the PCR products to characterize fully the sequence diversity. BAL T lymphocytes from two asthmatic patients (treated with inhaled steroids) expressed only VγII and, in one of them, VγIIJγ usage was restricted to JγP and JγP1 gene segments, contrasting with the VγJγ repertoire found in his respective PBL. Analyses in denaturing and non-denaturing gels showed that the BAL VγIIJγP and VγIIJγP1 PCR products resolved into few bands, suggesting deletions at the junctions due to oligoclonal expansion. BAL T lymphocytes from the third asthmatic (not receiving inhaled steroids) expressed VγI, II and III, and the sequences of the in-frame TCR transcripts from this asthmatic and one healthy volunteer who expressed a similar BAL Vγ TCR repertoire showed clonal expansion of T cells expressing all three Vγ families. Our analyses showed that much of the γδ T cell population found in BAL fluid of humans derives from clonally expanded T cells.

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