Reactions of anti-immunoglobulin sera with synthetic T cell receptor peptides: implications for the three-dimensional structure and function of the TCR β chain

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Abstract
The derived amino acid sequence of the human TCR β chain shows considerable homology to lg λ light chains in its variable (V) and constant (C) domains, and in its joining segment (J). We assessed the cross-reactivity between TCR β chains and lg light chains by synthesizing a set of nested, overlapping 16-mer peptides that duplicated the sequence that corresponds to the continuous VDJC sequence of TCR β chain and determining the capacity of rabbit antisera to human or murine lgs to react with these peptides. The reactivities we observed were consistent with homologies to λ and x light chains. The strongest reactivity in ELISA binding and competitive inhibition was with a peptide that corresponds to the ‘swtch peptide’ of light chains. The sequence is encoded by the C-terminal region of the J segment (Fr4) and the N-termlnus of the C region. Other regions reactive with anti-light chain sera corresponded respectively to CDR1 and Fr3 segments of the V region, and a segment of the constant region predicted to loop out of the tight globular structure. The peptide immunochemical results, coupled with the identification of specific regions of sequence correspondence between TCR β and the characterized λ light chain Mcg, allowed us to develop a three-dimensional model of the β chain consistent with its role in antigen recognition and response to superantigens.

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