T cell recognition of myoglobin. Localization of the sites stimulating T cell proliferative responses by synthetic overlapping peptides encompassing the entire molecule.

Abstract

A comprehensive strategy for the systematic localization of all continuous antigenic sites within a protein has previously been introduced by this laboratory. The strategy consists of studying the immunochemical activity of a series of consecutive synthetic peptides that encompass the entire protein chain and that are uniform in size and in overlap at their N- and C-terminals with neighbouring peptides. By application of this strategy to sperm whale myoglobin, we have been able to delineate the continuous sites of T cell recognition of myoglobin in three high responder mouse strains. Thirteen 17-residue peptides that encompass the entire myoglobin chain and overlap by five residues at both ends were synthesized, purified and characterized. The peptides were examined in vitro for their ability to stimulate lymph node cells from myoglobin-primed DBA/2 (H-2d), BALB/c (H-2d) and SJL (H-2s) mice as well as long-term cultures of myoglobin-specific T cells. Several regions of the molecule (T sites) were found to stimulate myoglobin-primed lymph node cells and myoglobin-specific longterm T cell cultures. This strategy has enabled the localization of the full profile of dominant sites of T cell recognition in myoglobin for these mouse strains. Of these T sites, one region, residues 107-125, was clearly immunodominant in these strains and was found to coincide with the antigenic (i.e. antibody binding) site 4 of myoglobin. Also, other regions stimulated T cells and appeared to coincide with previously known antigenic sites. It is noteworthy that, in addition to sites recognized by both T and B cells, the protein has other sites which are recognized exclusively by T cells and to which no detectable antibody response is directed.