Background: We have previously reported that gammadelta T cells are involved in the progression of IgA nephropathy (IgAN) to renal failure. Our current study examined the diversity of the CDR3 region of the gammadelta T-cell receptor (TCR), and characterized the junctional sequences of gammadelta chain TCR transcripts from T cells infiltrating renal biopsies from patients with IgAN and in peripheral blood T cells (PBLs) from the same patients.
Method: RNA extracted from renal biopsies and PBLs of IgAN patients (N = 15) was transcribed and then amplified with primers specific for the four Vgamma and six Vdelta families. Controls were renal biopsies from thin basement membrane disease (N = 6) and a sample from a kidney with suppurative pyelonephritis. CDR3 length spectratyping and sequencing of TCR gammadelta-chain were used to analyze the diversity of CDR3 region of these receptors.
Results: CDR3 spectratyping of gammadelta TCR junctional diversity demonstrated that TCR gammadelta chains (Vgamma1-3 and Vdelta1-3) expressed by T cells from PBLs of IgAN patients and the infected kidney showed highly diverse junctional lengths that were broadly distributed. In contrast, the junctional lengths of Vgamma1 (Vgamma2, 3, 4, 5, and 8 genes) and Vdelta1 transcripts in the T cells infiltrating kidneys with IgAN were much more restricted than those of PBLs. Renal biopsies from thin basement membrane disease demonstrated no significant signal for any Vgamma or Vdelta family. Sequence analysis of Vgamma1 and Vdelta1 transcripts from those patients with restricted CDR3 spectratyping profiles confirmed oligoclonal expansion of gammadelta T cells infiltrating the kidneys in those IgAN patients and also revealed recurrent junctional amino acid motifs in the TCR Vdelta1 chain in the kidney with IgAN.
Conclusion: The data show that gammadelta T cells infiltrating the kidneys of IgAN patients use a restricted subset of gammadelta T cells, indicating clonal expansion of individual gammadelta T cells in the kidneys with IgAN. The feature of recurrent junctional amino acid motifs in Vdelta1 T cells may indicate antigen-driven selection.