Identification of a major I-Ek-restricted determinant of hen egg lysozyme: limitations of lymph node proliferation studies in defining immunodominance and crypticity.
We have chemically analyzed the peptides presented by I-Ek molecules after processing of hen egg lysozyme (HEL) by a murine B-lymphoma line or by splenocytes. In both cases, the identified peptides were derived from a single region of HEL, containing the core residues 85-96 with heterogeneous N and C termini. This was a surprising result because this determinant had previously been described as cryptic--i.e., not presented after processing of intact HEL. Examination of the specificities of T hybridomas isolated after immunization with either HEL or 84-96 peptide (p84-96) provided an explanation for this controversy. Whereas hybridomas induced by immunization with HEL responded equally well to HEL and p84-96, those induced by peptide immunization showed a marked preference for p84-96 over intact HEL. In other words, hybridomas isolated after p84-96 immunization responded poorly to forms of the 84-96 determinant produced by natural processing, leading to the possible erroneous interpretation that 84-96 is a hidden determinant. We conclude that (i) p84-96 is efficiently presented on I-Ek molecules after processing of HEL, (ii) the explanation for the weak lymph node response to this epitope after immunization with HEL lies at the level of the T cell, not the antigen-presenting cell, and (iii) crypticity cannot be defined on the basis of T-cell proliferation studies alone.
Viner
N J
NJ
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.
Nelson
C A
CA
Unanue
E R
ER
D000595:Amino Acid Sequence; D000818:Animals; D000917:Antibody Formation; D002460:Cell Line; D002645:Chickens; D000939:Epitopes / Q000032:analysis*; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006825:Hybridomas / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology*; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D009113:Muramidase / Q000276:immunology*; D009842:Oligopeptides / Q000138:chemical synthesis / Q000276:immunology; D010063:Ovum / Q000201:enzymology; D010446:Peptide Fragments / Q000276:immunology* / Q000302:isolation & purification
D000939:Epitopes; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D009842:Oligopeptides; D010446:Peptide Fragments; D009113:Muramidase