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

Aims/Background: The liver-kidney-microsomal antigen (LKM-1) has been recog nized as a major CD4(+) T cell antigen in autoimmune hepatitis (AIH). The a im of this study was to characterize the antigen recognition sites of the v ariable T cell receptor beta -chain (TCRBV) of T cells specific to LKM-1. M ethods: By repeated stimulation of T cells with a recombinant LKM-1 antigen or an LKM-derived peptide followed by limited dilution, we generated T cel l clones. Usage of TCRBV was analyzed by RT-PCR and CDR3 antigen recognitio n sites were sequenced. Results. The 18 LKM-1 specific T cell clones isolat ed from six AIH patients preferentially expressed the TCR elements BV9, BV5 S2 + S3, BV6, and BV13S1. Four BV9+ T cell clones rearranged the joining el ement JB1S3 within their CDR3 regions. JB2S3 was detected in another four c lones 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 i dentify T cells expressing the preferred TCRBV molecules in situ, immunohis tologic examination of liver biopsies was performed. In AIH patients an acc umulation of T cells expressing TCRBV 13S1, BV8 and BV5S3 was observed. Con clusions. Our data define TCRBV restriction and preferred CDR3 features of LKM-1 specific T cells. The in situ localization of T cells expressing thes e restricted TCR molecules may suggest a pathogenic relevance of LKM-1 spec ific cellular immune responses.