T-cell repertoire in the blood and lungs of atopic asthmatics before and after ragweed challenge

T cells play a pivotal role in initiating and orchestrating allergic responses in asthma. The goal of this work was to learn whether ragweed challenge in the lungs alters the T-cell repertoire expressed in the blood and lungs of atopic asthmatics. Analyses of cell numbers, differentials, and T-cell subsets in bronchoalveolar lavage (BAL) fluids showed that ragweed challenge was associated with preferential recruitment of CD4⁺ T cells into the lungs. A reverse transcriptase-polymerase chain reaction (RT-PCR) was used to amplify T-cell receptor (TCR) gene transcripts from unfractionated, CD4⁺, and CD8⁺ T cells in blood and BAL fluids. As judged by RT-PCR, the usage of TCR Vα and Vβ gene families in BAL fluids was similar to that in blood. Ragweed challenge did not change the levels of expression of these V gene families. The clonality of T cells was estimated by analyzing the diversity of TCR V-(D)-J junctional region nucleotide lengths associated with each Vα and Vβ gene family, using sequencing gel electrophoresis. Most V gene families in blood and BAL fluids were associated with multiple junctional region lengths before and after ragweed challenge, indicating polydonal expression. Some V gene families were expressed in an oligoclonal manner in unfractionated. CD4⁺, and CD8⁺ T cells in BAL fluids before ragweed challenge, as indicated by a few predominant junctional region lengths. The majority of these V gene families became polyclonal after challenge, compatible with polyclonal T-cell influx during inflammation immediately after ragweed challenge. However, some V gene families became oligoclonal or developed a new oligoclonal pattern of junctional region lengths in BAL T cells after ragweed challenge. Surprisingly, this occurred in both CD4⁺ and CD8⁺ T cells. In one of these instances, DNA sequencing of Vβ21 junctional regions in CD8⁺ T cells confirmed a change from polyclonal to oligoclonal expression after ragweed challenge. These findings show that ragweed challenge is associated with polyclonal influx and oligoclonal activation of both CD4⁺ and CD8⁺ T cells in the lungs.