Presentation of endogenous acetylcholine receptor antigen to a specific CD4+ T-cell line by a transfected B-cell line.

Currently, the limited supply and stability of some human autoantigens pose formidable difficulties in characterizing patients' T cells specific for them; recombinant preparations may contain bacterial contaminants, and synthetic peptides have arbitrarily chosen start and stop points. In order to provide a stable antigen source with naturally processed epitopes, a full-length acetylcholine receptor (AChR) alpha subunit construct was transfected into B-lymphoblastoid cell lines (B-LCL). Expression was much easier to detect at the mRNA level than the protein level. Nevertheless, this transfectant also stimulated a T-cell line that recognized the alpha 149-156 region in the context of HLA-DR4 at high sensitivity. The responses were specific both for the antigen transfected and for the presenting HLA-DR allele. This study thus confirms the potential of autologous B-LCL expressing natural epitopes in the context of HLA class II molecules for characterizing established T-cell lines, and perhaps also for initiating new ones.