title: Major histocompatibility complex regulation of T helper functions mapped to a peptide C terminus that controls ligand density.
abstract: The functional status (Th1- versus Th2-like) of CD4 T cells primed against human collagen type IV (hCol IV) or a single 30mer peptide from the alpha 2 chain of this molecule is predicted by the major histocompatibility complex (MHC) class II (I-A) genotype of the responding mice. H-2s mice elicit Th1-like cell-mediated responses to these antigens, whereas Th2-like humoral responses are primed in H-2b,d,k mice. We now report that the ability of MHC to dictate T helper function in this system depends upon a single amino acid of the minimal alpha 2(IV) peptide. The C terminus of this minimal (12mer) peptide is -G-G-P-K, which is predicted to form a beta-turn. The present data demonstrate that the terminal lysine (K) stabilizes the immunogens full biological effects necessary for exclusive cell-mediated responses in H-2s mice. The lysine-truncated (11mer) peptide with otherwise identical sequence effectively primes T helper function in both H-2b and H-2s genotypes. Most importantly, our direct analysis of these peptides' presentation by live antigen-presenting cells (APC) reveals that the 12mer is bound at a log higher density on H-2s APC than on H-2b APC, and that the 11mer is presented at an equally low relative density on APC from both genotypes. In vitro analyses of 12mer/11mer cross-reactive Th clones demonstrate that I-As restricted clones require about 1-2 log lower doses of 12mer peptide than 11mer peptide to stimulate equivalent thymidine incorporation and cytokine release. By contrast, I-Ab-restricted (12mer/11mer cross-reactive) Th clones show no preference for the 12mer and require relatively high peptide doses similar to those required to stimulate the I-As clones with the 11mer peptide. Thus, the peptide dose requirements of Th clones reflect the high density of presentation associated with the 12mer: I-As ligand. Taken together, the results directly support the role of ligand density as an important control point in the functional decision of CD4 T cells.
authors.affiliation: Division of Biology, Kansas State University, Manhattan 66506.
authors.forename: J S
authors.initials: JS
authors.lastname: Murray
authors.forename: D
authors.initials: D
authors.lastname: Ferrandis-Edwards
authors.forename: C J
authors.initials: CJ
authors.lastname: Wolfe
authors.forename: T
authors.initials: T
authors.lastname: Schountz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003094:Collagen / Q000737:chemistry / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D006183:H-2 Antigens / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex / Q000276:immunology; D008297:Male; D051379:Mice; D008805:Mice, Inbred A; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D017433:Protein Structure, Secondary; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D006183:H-2 Antigens; D000949:Histocompatibility Antigens Class II; D010455:Peptides; D003094:Collagen