Analysis of peripheral blood mononuclear cell stimulated with pyruvate dehydrogenase complex, T-cell receptors from patients with primary biliary cirrhosis

Pyruvate dehydrogenase specific T cells in primary biliary cirrhosis show restricted antigen recognition sites

BACKGROUND/AIMS

The aim was to characterise the antigen recognition sites of the variable T cell receptor alpha-chain (TCRAV) and beta-chain (TCRBV) of T cells specific to the pyruvate dehydrogenase (PDC) in primary biliary cirrhosis.

METHODS

In 21 PDC-specific T cell clones isolated from five patients we analysed TCRAV and TCRBV usage by RT-PCR and sequenced the CDR3 regions.

RESULTS

Preferential expression of the TCR elements BV6 (6 clones), BV12 (4 clones) and BV1 (3 clones), and frequent usage of the joining elements JB2.3 and JB2.1 were seen. Analysis of the alpha chain revealed rearrangement of AV2 in 7 clones (35%) and AV7 in 3 clones, however, distribution of the joining elements was heterogenous and no common sequence motifs were detected. Evaluation of the physicochemical properties of the beta-chain demonstrated a positive charge at position P4 in several clones of two patients and a hydrophobic residue at position P5 in two different patients. Further, a conserved glycine at position P7 and neutral residues at positions P6 and P8 were frequently detected.

CONCLUSIONS

Our data define TCR variable region restriction and preferred CDR3 features of PDC-specific T cells and support the notion that few relevant epitopes on the PDC complex are recognised by selected T cells.

T cell repertoire in primary biliary cirrhosis: a common T cell clone and repertoire change after treatment

T cell repertoire was analyzed in three early-stage primary biliary cirrhosis (PBC) patients, using reverse transcription-polymerase chain reaction and single-strand conformation polymorphism. Multiple expanded clones were demonstrated in livers and peripheral blood lymphocytes (PBL) of all three patients. Comparison of the repertoire of different parts of the liver demonstrated the presence of common clones in various Vbeta families. Comparison of the repertoire between the liver and PBL demonstrated that both CD4 and CD8 T cell clones were expanded. Sequence analysis of complementarity determining region 3 of the expanded clones revealed that relatively conserved amino acids were utilized in each patient and that an identical CD4 T cell clone having Vbeta16 was present in all three patients. The number of expanded T cell clones in PBL decreased markedly after the treatment with prednisolone. These results suggest that common T cell clones may play a pathogenic role in PBC.

T cell repertoire in the liver of patients with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune chronic liver disease characterized by the destruction of the bile ducts with an accumulation of lymphocytes. To investigate the roles of T cells accumulating around the bile ducts, we analyzed the clonality of alphabeta T cell populations in the livers of patients with PBC by size spectratyping and sequencing of the T cell receptor (TCR) Vbeta transcripts.TCR Vbeta spectratyping of PBC patients showed several skewed complementarity determining region 3 (CDR3) size patterns suggestive of clonal predominance as well as Gaussian-like patterns suggestive of polyclonal expansion. We observed Vbeta4 clones sharing the Gly (G)-G motif in the CDR3 nDn regions and a Vbeta4-Jbeta2.7 combination in three patients bearing HLA-DR2 and -DQ1. G-Leu (L)-Ala (A) or G-L motifs were also seen in the nDn regions of Vbeta17 with Jbeta2.1 of the two patients having HLA-A26. However, there were no whole CDR3-shared clones in any of the patients. In conclusion, we have observed that T cell clones are heterogeneous in each patient, but that they have some common motifs in the TCR Vbeta CDR3. We strongly suggest that these clonally expanded T cells might be involved in the immunopathogenesis of PBC.