T cell receptor Vβ chain restriction and preferred CDR3 motifs of liver‐kidney microsomal antigen (LKM‐1)‐reactive T cells from autoimmune hepatitis patients

Abstract: Aims/Background: The liver‐kidney‐microsomal antigen (LKM‐1) has been recognized as a major CD4⁺ T cell antigen in autoimmune hepatitis (AIH). The aim of this study was to characterize the antigen recognition sites of the variable T cell receptor β‐chain (TCRBV) of T cells specific to LKM‐1. Methods: By repeated stimulation of T cells with a recombinant LKM‐1 antigen or an LKM‐derived peptide followed by limited dilution, we generated T cell clones. Usage of TCRBV was analyzed by RT‐PCR and CDR3 antigen recognition sites were sequenced. Results: The 18 LKM‐1 specific T cell clones isolated from six AIH patients preferentially expressed the TCR elements BV9, BV5S2+S3, BV6, and BV13S1. Four BV9+ T cell clones rearranged the joining element JB1S3 within their CDR3 regions. JB2S3 was detected in another four clones together with BV5S2+S3 or BV13S1. A conserved sequence motif, Q(N)G(X)N, was seen in the diversity regions of five clones (36%). In order to identify T cells expressing the preferred TCRBV molecules in situ, immunohistologic examination of liver biopsies was performed. In AIH patients an accumulation of T cells expressing TCRBV 13S1, BV8 and BV5S3 was observed. Conclusions: Our data define TCRBV restriction and preferred CDR3 features of LKM‐1 specific T cells. The in situ localization of T cells expressing these restricted TCR molecules may suggest a pathogenic relevance of LKM‐1 specific cellular immune responses.