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The (NZB x NZW)F1 mouse strain develops a syndrome of accelerated autoimmunity including severe renal disease and early death. Evidence suggests that class II molecules play a central role in this process. Previous studies have suggested that the NZW strain contributes at least one gene to the development of accelerated autoimmunity that is linked to the H-2 complex, and antibodies to murine class II molecules have been used to ameliorate disease in (NZB x NZW)F1 mice. We therefore wished to sequence the class II molecules from NZW mice to identify any unique sequences that may contribute to disease development. We constructed oligonucleotide primers corresponding to the 5' and 3' regions of the second exon of class II genes from a variety of haplotypes, and used these primers in a polymerase chain reaction to sequence the second exon of the NZW I-A alpha, I-A beta, and I-E beta genes. We report that the second exons of NZW I-A alpha, I-A beta, and I-E alpha are identical to their counterparts of the previously sequenced u haplotype, and that the second exon of NZW I-E beta is identical to its counterpart from u except for a single base change that results in a substitution of arginine for threonine at amino acid 72. This base and amino acid are identical to those found at the same positions in the s haplotype.

SummaryThe A/Japan/57 influenza hemagglutinin (HA) peptide HA 128-145, when bound by human histocompatibility leukocyte antigen-DRw11 cells, is recognized by the human CD4+ T cell clone V1. A rabbit antiserum has been raised against HA 128-145 which recognizes not only the free peptide, but also the HA 128-145/DRw11 complex on a solid matrix, in solution, or on the surface of viable cells. The detection of these complexes on viable cells was shown to be class II specific, DRw11 restricted, and commensurate with the level of DRw11 expression. The identity of DRw11 as the cell surface molecule binding HA 128-145 was confirmed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and tryptic peptide mapping. Using this antiserum, HA 128-145/DRw11 complexes could be detected on the cell surface as soon as 30 min after the peptide was added, and increased up to 24 h. Dissociation kinetics showed these complexes were long-lived, with a half-life of approximately 14 h. This anti-HA peptide antiserum represents the first direct means of studying antigenic peptide-human leukocyte antigen class II complexes on the surface ofliving cells without the addition of a nonamino acid moiety to the peptide. The properties of this antiserum thus provide the potential to study naturally processed antigenic peptides as well as the mechanism of processing itself in a physiologically relevant system . T he immune response of CD4+ T cells is thought to be triggered by immunogenic MHC class II moleculepeptide complexes present on the surface of APC's (1-5). Previous reports have demonstrated in vitro association of peptide antigen with purified class II molecules (5-10), and proliferation of cloned T cells exposed to these complexes (6, 11) .While antigen-specific T cells have been useful for qualitatively demonstrating the presence of such complexes, the low number of surface peptide-class II complexes needed to activate a T cell, and the all-or-none nature of the recognition event have made such assays less useful for studying the kinetics and nature ofpeptide-class II binding (12)(13)(14). Studies of APC antigen processing and class II loading have been hampered by the inability to directly detect peptide bound in the antigen-binding groove ofthese molecules on the surface ofintact cells. Whole cell binding assays using radiolabelled peptide antigen have been plagued by nonspecific uptake of radiolabel into the cells . Those studies which promote metabolic antigen-processing have suffered from unacceptably high levels of nonspecific binding which have made it difficult to separately study the complexes of peptide antigen bound to surface class II molecules . Similar studies done under conditions which block APC intracellular antigen uptake and processing have demonstrated a high level of nonspecific cell surface binding and only a low level of binding to class II molecules (7,(15)(16)(17)(18)(19)(20) .A series of rather elegant studies using biotinylated peptides and a fluorescent-avidin detection system h...

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