To determine whether monoclonal/oligoclonal T cells are present in abdominal aortic aneurysm (AAA) lesions, we amplified beta-chain T cell receptor (TCR) transcripts from these lesions by the nonpalindromic adaptor (NPA)-polymerase chain reaction (PCR)/V-beta-specific PCR followed by cloning and sequencing. Sequence analysis revealed the presence of substantial proportions of identical beta-chain TCR transcripts in AAA lesions in 9 of 10 patients examined, strongly suggesting the presence of oligoclonal populations of alphabeta TCR+ T cells. We have also shown the presence of oligoclonal populations of gammadelta TCR+ T cells in AAA lesions. Sequence analysis after appropriate PCR amplification and cloning revealed the presence of substantial proportions of identical VgammaI and VgammaII TCR transcripts in 15 of 15 patients examined, and of Vdelta1 and Vdelta2 TCR transcripts in 12 of 12 patients. These clonal expansions were very strong. All these clonal expansions were statistically significant by the binomial distribution. In other studies, we determined that mononuclear cells infiltrating AAA lesions express early- (CD69), intermediate- (CD25, CD38), and late- (CD45RO, HLA class II) activation antigens. These findings suggest that active ongoing inflammation is present in the aortic wall of patients with AAA. These results demonstrate that oligoclonal alphabeta TCR+ and gammadelta TCR+T cells are present in AAA lesions. These oligoclonal T cells have been clonally expanded in vivo in response to yet unidentified antigens. Although the antigenic specificity of these T cells remains to be determined, these T cells may play a significant role in the initiation and/or the propagation of the AAA. It appears that AAA is a specific antigen-driven T cell disease.
T-cell involvement may be central to the pathogenesis of systemic sclerosis (SSc). Like αβ TCR+ T-cells, γδ TCR+ T-cell diversity during T-cell development results in a repertoire of different T-cells each with a unique TCR. Therefore the probability of finding identical TCR on defined T-cell populations is negligible, except in the context of an antigen-driven T-cell response. To determine whether γδ TCR+ T-cells are clonally expanded in skin biopsies and/or peripheral blood of patients with SSc (n=7), γ-chain (VγI & Vγ9) and δ-chain (Vδ1 & Vδ2) TCR transcripts were amplified by gene-specific PCR, followed by cloning and sequencing. We report the presence of substantial proportions of identical VγI-chain transcripts (14.3%-37.2%; p<0.05), and Vγ9 transcripts (24%-83.3%; p<0.05) in skin biopsies and/or PBMC of patients with SSc. Likewise, there were multiple identical Vδ1-chain transcripts (25%-50%; p<0.05), and Vδ2-chain transcripts (18.1%-80%; p<0.05) in the samples analyzed. Extensive clonal expansions of γ- and δ-chain TCR transcripts were identified in skin biopsies and peripheral blood of patients with SSc, demonstrating the presence of oligoclonal populations of γδ TCR+ T-cells in these patients. These γδ TCR+ T-cells may have undergone activation and clonal expansion in vivo in response to as yet unidentified antigens. Future studies to identify the antigens recognized by these clonally expanded γδ TCRs will facilitate better understanding of SSc pathogenesis.
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