title: Processing by accessory cells for presentation to murine T cells of apamin, a disulfide-bonded 18 amino acid peptide.
abstract: Apamin, an 18 amino acid peptide with two disulfide bonds, elicits specific T cell proliferative responses in H-2d and H-2b mouse strains. We evaluated the processing requirement of this compact peptide by accessory cells for presentation to apamin-reactive T hybridoma cells (THC) by analyzing the IL-2 responses of 16 THC from apamin-primed BALB/c or C57BL/6 mice, to various forms of either native or chemically synthesized apamin analogs. These included: unfolded peptides (whose four sulfhydryl groups were blocked by acetamidomethyl residues), N-and/or C-truncated peptides, and an analog with a single amino acid substitution at position 10. Assessment of the Ag-specific THC responses in the presence of either live or formaldehyde-prefixed APC indicated the following: 1) all THC stringently required Ag processing; 2) in 8 of 16 cases, the simple unfolding of apamin was sufficient to eliminate the need for Ag processing, or even induced increased THC IL-2 responses (other cells required further antigenic alterations in addition to unfolding, or rare processing steps dependent on the integrity of the two disulfide bonds); and 3) for most THC, the Leu10 and the N terminus arm of apamin were shown to be critical for expression of the epitopes involved in T cell recognition. These data indicate that apamin, a natural peptide having an appropriate size for T cell triggering, acquires its antigenic conformation after a processing by APC which primarily involves an alteration of a disulfide bond-dependent peptide folding.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000378:metabolism*; D001030:Apamin / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000276:immunology*; D001514:Bee Venoms / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D005260:Female; D007376:Interleukin-2 / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011487:Protein Conformation; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D001514:Bee Venoms; D000939:Epitopes; D007376:Interleukin-2; D001030:Apamin