Primary structure of murine major histocompatibility complex alloantigens: amino acid sequence of the amino-terminal one hundred and seventy-three residues of the H-2Kb glycoprotein

Analysis of the H-2Kbm8 mutant: correlation of structure with function

The gene for H-2K class I major histocompatibility antigen on the bm8 variant was cloned and the DNA sequence compared with the parental gene. Sequence analysis demonstrated that seven nucleotides were changed with respect to the parental gene sequence spanning 24 nucleotides. These changes represent an alteration of four amino acids from the parent protein. As this mutation occurred in a single generation, a potential donor gene for such a complex mutation was suggested and identified. The Q4 gene class I-like molecule has a stretch of 95 nucleotides of identity in the region of the bm8 mutation. Genomic Southern analysis of the mutant and parental DNA with a gene-specific oligonucleotide demonstrated that the potential donor gene Q4 is a likely candidate sequence for such an event. The amino acid alterations for the H-2Kbm8 mutation are discussed in consideration of hte three-dimensional structure of the characterized human class I glycoprotein.

Immunoglobulin heavy chain class switch from IgM to IgG in a hybridoma

A subclone of an IgM-producing hybridoma has been identified which has switched to producing an IgG1 antibody. The parent hybridoma, PC-140, produces an antibody which binds phosphorylcholine and reacts with monoclonal antibodies that recognize myelomas of the T-15 idiotype. The IgG1 antibody binds phosphorylcholine with the same affinity as the parental IgM and also reacts with the anti-T-15 monoclonal antibodies. While the IgM-producing parent hybridoma does not express detectable surface IgM, the IgG1-producing subclone produces both membrane and secreted IgG1.

Amino acid sequence of the cytoplasmic segment of the h-2Kd (H2.31) murine major histocompatibility antigen

The primary structure of the carboxy-terminal portion of the H-2Kd murine major histocompatibility antigen has been determined using radiosequencing methodology. The two peptides encompassing the entire cytoplasmic portion of the H-2Kd molecule were isolated from cyanogen bromide digests of the detergent solubilized molecule. These two peptides are not present in CNBr digests of papain-solubilized H-2Kd. Alignment of the two CNBr peptides was deduced from tryptic overlap peptides derived from the whole molecule. Alignment with the corresponding region of the H-2Kb antigen shows 90% homology and supports the assignment of this segment of H-2Kd as the C-terminal. The sequence obtained in this study is (Met)-Arg-Arg-Asn-Thr-Gly-Gly-Lys-Gly-Val-Asn-Tyr-Ala-Leu-Ala-Pro-Gly-Ser-Gln- Thr-Ser-Asp-Leu-Ser-Leu-Pro-Asp-Pro-Lys-Val-Met-Val-His-Asp-Pro-His-Ser-Leu- Ala. These data allow extensive comparisons with the protein sequences deduced from the 3' ends of H-2d haplotype cDNA and genomic clones as well as with the homologous regions of H-2Kb and H-2Db.

Biochemical studies of H-2K antigens from a group of related mutants. II. Identification of a shared mutation in B6-H-2bm6, B6.C-H-2bm7, and B6.C-H-2bm9

In an earlier paper, we presented evidence that two independent mutants of the bg series, B6-H-2bm5 (bm5) and B6-H-2bm16 (bm16) carry identical mutations such that tyrosine at residue number 116 of the H-2Kb molecule from the parent strain C57BL/6Kh is replaced by a phenylalanine in each of the two mutant molecules. In this paper, we demonstrate, using similar techniques, that the independent bg series mutants B6-H-2bm6 (bm6), B6.C-H-2bm7 (bm7), and B6.C-H-2bm9 (bm9), which share biological properties with bm5 and bm16, can be grouped together because they share two identical mutations, one of which is common to bm5 and bm16, a Tyr to Phe interchange at residue number 116. In addition, a second mutation is at residue number 121, where a Cys in the H-2K molecule from B6 is substituted with an Arg in the mutant. Since all of the bg series mutants arose independently and share biological and biochemical characteristics, it is anticipated that study of these mutants could lead to some understanding of the high mutation rate in the Kb molecule.

Biochemical studies of H-2K antigens from a group of related mutants. I. Identification of a shared mutation in B6-H-2bm5 and B6-H-2bm16

Structural studies of the H-2 gene products from a group of five closely related but independent C57BL/6H-2 mutant mice were undertaken. Each of the mutants exhibits reciprocal graft rejection with the parent. The group is remarkable, however, because each member of this group can accept skin grafts from any other member. The results of biochemical analysis of the H-2 glycoproteins from two of these related mutants, bm5 and bm16, are presented in this report. Evidence is given that the H-2K molecules from these two mutants are identical to each other based on comparative tryptic peptide mapping profiles with the parent. From partial amino acid sequence analysis, K products of both mutants have at least one common difference from the parental type located at residue number 116. Definitive studies established that in both bm5 and bm16 a tyrosine found in the parent molecule is substituted with a phenylalanine in the mutant. These results show that a biochemical difference between the K products of the two mutants and of the parent can be detected, that the mutants appear to be identical with one another even though they arose independently, and that they differ from the other H-2Kb mutants analyzed.

Biochemical studies on the H-2K mutant B6.C-H-2bm10

The H-2K glycoprotein from the MHC mutant bm10 was analyzed biochemically to determine where primary structural differences distinguished it from the parental standard molecule, Kb. Comparative peptide maps showed differences in two peptides known to be part of the parental CNBr fragment spanning amino acids 139 to 228. Partial sequence analyses of CNBr fragments and tryptic peptides identified two tightly clustered amino acid substitutions at amino acids 165 (Val to Met) and 173 (Lys to unknown). The substitutions in bm10 represent the most carboxy-terminal substitutions characterized in the Kb molecules of the spontaneous, histogenically active H-2 mutants.

Biochemical comparison of major histocompatibility complex molecules from different subspecies of Mus musculus: evidence for trans-specific evolution of alleles

H-2 haplotypes were extracted from wild mice of three subspecies, Mus musculus domesticus, M. m. molossinus, and M. m. castaneus, that are known to have been separated from one another for some 1 to 2 million years. Serologically indistinguishable molecules controlled by some of the polymorphic H-2 loci were compared by tryptic peptide mapping, and the maps were found to be identical. In addition, a number of instances of biochemically indistinguishable H-2 molecules were found among wild mice and inbred strains of the M. m. domesticus subspecies. These findings suggest that some of the H-2 alleles have not altered for greater than 1 million years. To reconcile this apparent stability of H-2 genes with their extraordinary polymorphism (some 100 alleles at each of the polymorphic H-2 loci), it is proposed that the H-2 alleles evolve as if they were separate loci.

The 48-base-long primordial building block of immunoglobulin light-chain variable regions is complementary to the primordial building block of heavy-chain variable regions

The ancestral gene for immunoglobulin light-chain variable regions (Ig VLs) of the kappa as well as the lambda class apparently arose from about 12 tandem repeats of the 48-base-long primordial building block sequence TCT-TGC-GCA-GTA-AGT-CCA-CTC-CAG-GTC-ATA-TCC-AGT-CAG-GCT-GCT-GAA. Even today, amino acid residues 67 to 82 of each Ig V kappa L are still specified by a direct descendant in toto of the above-noted primordial building block, whereas amino acid residues 14 to 25 are invariably specified by its truncated copy. The Ig VL primordial building block presently identified is 100% complementary to the Ig VH (heavy-chain variable region) primordial building block previously identified. In the recognition of specific antigenic determinants by antibodies, Ig VL and Ig VH of light-chain--heavy-chain dimers have to complement each other. It is perhaps fitting that the primordial building blocks of the two are represented by the complementary strands of the same 48-base-pair-long DNA sequence.

Primary structure of the H-2Db alloantigen. II. Additional amino acid sequence information, localization of a third site of glycosylation and evidence for K and D region specific sequences

The complete amino acid sequence of the CNBr fragment comprising residues 229-284 of the murine major histocompatibility complex antigen H-2Db has been determined using radiochemical methodology. The sequence was determined by N-terminal sequence analysis of the intact CNBr fragment and by sequence determinations of peptides derived from this fragment by trypsin and staphylococcal V8 protease cleavage. In addition to the amino acid assignments for H-2Db, it was possible to assign the linkage position of the third N-linked glycosyl unit to the asparagine at residue 256. Additional amino acid sequence assignments have also been made for three other CNBr fragments that span residues 99-138, 139-228, and 308-331 of the H-2Db molecule. The total protein sequence information available (222 of 338 residues) agrees in every comparable position with the protein sequence derived from the cDNA clone (pH203) isolated by Reyes and co-workers (1982b), which strongly suggests that this clone encodes H-2Db. Combination of the protein sequence with that deduced from the cDNA clone provides the complete H-2Db protein sequence. Comparison of this sequence with other available protein sequence information for murine class I molecules has revealed protein sequences that may be unique to either K or D region molecules.

The H-2Kk antigen: isolation using monoclonal immunoadsorbent chromatography and sequence analysis without radioisotopes

Monoclonal immunoadsorbent chromatography has been used to isolate milligram quantities of detergent-solubilized H-2Kk antigen. Using the procedure described in this paper 10(12) cells may be processed yielding 10 mg of homogenous H-2Kk which represents 70% of the allotypic serological activity present in the original homogenate. NH2-Terminal sequence data of the first 30 residues of the H-2Kk heavy chain are presented. The cell line selected as the source of antigen and the criteria of purity of the antigen have been found to be critical as proteins of molecular weight 42,000 and 12,000 were copurified with H-2Kk from the BW5147 cell line. The additional components were observed in gradient gel electrophoresis or two-dimensional electrophoresis, but not in conventional Laemmli gel electrophoresis.

The complete amino acid sequence of the murine transplantation antigen H-2Db as deduced by molecular cloning

A mouse cDNA library derived from the EL4 cell line (b-haplotype) was screened with a probe containing a small part of the H-2Kb coding region. One of the clones isolated, pH203, encodes a protein whose deduced amino acid sequence is identical with the known sequence of H-2Db in 141 of 141 positions available for comparison. The clone, therefore, is believed to code for the H-2Db transplantation antigen. The cDNA insert of pH203 contains the coding region for residues 82 through the carboxy-terminus of H-2Db, and includes 476 nucleotides of the 3'-untranslated sequence. Comparison between the H-2Db cDNA clone and a previously isolated H-2Kb cDNA clone shows homologies of 83% and 91% at the amino acid and nucleotide levels, respectively. Analysis of DNA sequences at the 3'-coding and untranslated regions suggests that the mRNAs of H-2Kb and H-2Db are spliced differently at their 3'-coding ends.

Biochemical studies on the H-2K antigens of the MHC mutant bml

Biochemical analysis of the H-2K-gene product from the MHC mutant strain bml and from the C57BL/6 parent strain has been carried out in order to characterize the structural differences between parent and mutant K-gene products. Based on comparative tryptic peptide mapping of the cyanogen bromide fragments from these glycoproteins, two peptide differences were localized to the CN-Ia fragment. Partial amino-acid sequence analysis revealed two alterations in the primary structure of Kbml involving substitutions of tyrosine for arginine at position 155, and tyrosine for leucine at position 156. Both of these amino-acid replacements require a minimum of two nucleotide base changes at the nucleic acid level. These changes were the only alterations noted differentiating the Kbml and Kb glycoproteins. However, because our techniques allow us to analyze only 75 to 80 percent of the extra cellular portion of H-2Kb, it is possible there are other undetected changes. Nonetheless, the biochemical data are consistent with the hypothesis that the structural alterations noted in the Kbml mutant glycoprotein are directly related to the observed immunological specificity relative to the parent Kb molecule. Peptide comparisons of the Kb molecules of two C57BL/6 sublines and of the H-2b lymphoblastoid cell line, EL-4, disclosed no difference.

Possible conformation of major histocompatibility antigens: implication of amino acid sequence data

Possible conformation of major histocompatibility antigens was proposed on the basis of homology between domains of major histocompatibility antigen polypeptide chains and domains of immunoglobulins, characterized by a beta-pleated structure. In the hypothetical three-dimensional structure, domains alpha 3 and alpha 2 interact along the chain similarly to the CH2 and CH3 domains of IgG. beta 2-Microglobulin together with domain alpha 2 forms a structure analogous to the CH3--CH3 or CH1--CL dimers in IgG. Domains alpha 2 ans alpha 1 interact in such a manner that the beta-pleated sheet of domain alpha 2 is directly joined to the beta-pleated sheet of domain alpha 1. Hypervariable regions in domains alpha 1 and alpha 2, which most likely take part in the formation of the alloantigen determinants, represent the loops joining the regions of the beta-pleated structure. Domains alpha 1 and alpha 2 may be packed in such a way that their hypervariable regions would become adjacent and would be located on their surface turned aside from the surface of the cell membrane.

Amino acid sequence of the carboxyl-terminal hydrophilic region of the H-2Kb MHC alloantigen. Completion of the entire primary structure of the H-2Kb molecule

The amino acid sequence of the COOH-terminal hydrophilic region of the H-2Kb histocompatibility antigen was determined. The sequence was completed by analyses of four CNBr fragments obtained from the intact molecule as well as tryptic peptides. This region was composed of 39 amino acid residues with a cluster of basic residues at the NH2 terminus and localized positions 308-346 of the H-2Kb molecule. These sequence data, together with those reported for the NH2-terminal 284 residues [Martinko, J. M., Uehara, H., Ewenstein, B. M., Kindt, T. J., Coligan, J. E., & Nathenson, S. G. (1980) Biochemistry 19, 6188-6193] and for the intramembranous segment [Uehara, H., Coligan, J. E., & Nathenson, S. G. (1981) Biochemistry (preceding paper in this issue)], provided the complete primary structure of the H-2Kb molecule. This is the first histocompatibility antigen for which the entire primary structure is determined.

Isolation and sequence analysis of the intramembranous hydrophobic segment of the H-2Kb murine histocompatibility antigen

The primary structure of the intramembranous segment (TC-1) of the mouse transplantation antigen, H-2Kb, has been determined. The segment contains a stretch of 31 uncharged amino acid residues and is localized between the NH2-terminal and the COOH-terminal hydrophilic regions of the molecule. The amino acid sequence of TC-1 is Trp-Asp-Glu-Pro-Pro-Ser-Thr-Val-Ser-Asn-Met-Ala-Thr-Val-Ala-Val-Leu-Val-Val-Leu -Gly-Ala-Ala-Ile-Val-Thr-Gly-Ala-Val-Val-Ala-Phe-Val-Met-Lys-Met-Arg-(Arg)-(Arg ).

Similar amino acid sequences: chance or common ancestry?

The systemic comparison of every newly determined amino acid sequence with all other known sequences may allow a complete reconstruction of the evolutionary events leading to contemporary proteins. But sometimes the surviving similarities are so vague that even computer-based sequence comparisons procedures are unable to validate relationships. In other cases similar sequences may appear in totally alien proteins as a result of mere chance or, occasionally, by the convergent evolution of sequences with special properties.

Two kappa immunoglobulin genes are expressed in the myeloma S107

We have cloned two rearranged kappa immunoglobulin genes from the mouse myeloma cell line S107, and find that both are expressed. One gene, designated S107A, encodes the secreted kappa chain that participates in phosphocholine binding and expression of the T-15 idiotype. The other gene, designated S107B, as described here, contains an unusual junction between a V region unrelated to that of S107A and a different J region. The V-J junction preserves the triplet reading frame, but 6 nucleotides have been deleted at the recombination site. Nucleotide sequence analysis of the germline V-region precursor of S107B in comparison with other germline kappa-variable sequences reveals an "extra" 2 nucleotides in S107B between codon 95 and the palindromic heptanucleotide CACAGTG previously implicated in V-J recombination; this difference may be relevant to the 6 nucleotide deletion. Both S107A and S107B genes are expressed in the S107 cell as protein products, but unlike the S107A kappa chain, the S107B protein product is not secreted into the medium. The expression of these two kappa genes in the S107 cell has implications for theories of allelic exclusion.

Interspecies exchange of beta 2-microglobulin and associated MHC and differentiation antigens

Radiolabeled human beta 2-microglobulin (beta 2m) can bind to mouse histocompatibility (H-2) antigens on the cell surface or to partially purified H-2 antigens in solution. The complexes containing human beta 2m and H-2 antigens from C3H (H-2k) mice could be immunoprecipitated specifically with alloantisera, rabbit anti-H-2 xenoantisera, and with monoclonal H-2-specific antibodies. Specific association with H-2 antigens was also observed with other haplotypes. The only exception was B10.D2 (H-2d) from which complexes containing human beta 2m could only be precipitated with anti-H-2-xenosera. Thus radiolabeled human beta 2m can be used as a specific label for mouse H-2 antigens in precipitation and radioimmunoassays. The application of this finding extends to major histocompatibility complex antigens of other species, and to differentiation antigens with primary association with beta 2m.

cDNA clone coding for part of a mouse H-2d major histocompatibility antigen

mRNA coding for mouse major transplantation antigens of the d haplotype was partially purified, copied into double-stranded cDNA, and cloned in Escherichia coli. Clones were selected by their ability to hybridize specifically with mRNA coding for H-2K, D, or L antigens. One of these clones, pH-2d-1, carries a 1200-base-pair insert, comprising the noncoding region, including poly(A) at the 3' end and part of the coding region. A partial sequence of the latter region showed extensive homology with the known amino acid sequences of H-2Kb,Kk, and HLA-B7 antigens. From this comparison, it appears that the coding region extends from amino acid 133 in the second domain, through the third domain, to the cytoplasmic COOH-terminal region. A stretch of 24 hydrophobic or uncharged residues, located 31 amino acids from the COOH-terminal end, could represent the segment that spans the membrane. This is followed on the cytoplasmic side of the membrane by a cluster of basic amino acids and a possible phosphorylation site on a threonine residue.

Cross-reactivity between human and murine lymphocyte antigens. IV. Reactivity of H-2 alloantisera with HLA-A, B antigens

The anti-H-2 alloantiserum D-32 [(B10.A(2R) x C3H.SW) anti-C3H] is cytolytic to human lymphocytes. Fab2 blocking assays, indirect immunoprecipitation and sequential immunoprecipitation experiments showed that the anti-H-2 alloantiserum D-32 recognizes antigenic determinants which are expressed on the heavy chain of subpopulations of HLA-A, B antigens. These determinants are different from those defining the serological polymorphism of the HLA-A, B, C system, are the same as or spatially close to those recognized by the anti-HLA-A, B monoclonal antibody Q6/64 and are expressed on rabbit, rat or guinea pig lymphocytes.

Complete amino acid sequence of murine beta 2-microglobulin: structural evidence for strain-related polymorphism

Primary structural analyses of beta 3-microglobulin isolated from the tumor cell lines EL4.BU (derived from a C57BL/6 mouse) and C14 (derived from a BALB/c mouse) have revealed the presence of an amino acid difference at position 85 of this molecule. beta 2-Microglobulin isolated from histocompatibility antigens of EL4.BU has alanine at this position, whereas that from C14 has aspartic acid. Determination of the sequence of these molecules has employed radiochemical methodology that was developed in studies of murine histocompatibility antigens. The sequence obtained in this study is: Ile - Gln - Lys - Thr - Pro - Gln - Ile - Gln - Val - Tyr - Ser - Arg - His - Pro - Pro - Glu - Asn - Gly - Lys - Pro - Asn - Ile - Leu - Asn - Cys - Tyr - Val - Thr - Gln - Phe - His - Pro - Pro - His - Ile - Glu - Ile - Gln - Met - Leu - Lys - Asn - Gly - Lys - Lys - Ile Pro - Lys - Val - Glu - Met - Ser - Asp - Met - Ser - Phe - Ser - Lys - Asp - Trp - Ser - Phe - Tyr - Ile - Leu - Ala - His - Thr - Glu - Phe - Thr - Pro - Thr - Glu - Thr - Asp - Thr - Tyr - Ala - Cys - Arg - Val - Lys - His - Ala/Asp - Ser - Met - Ala - Glu - Pro - Lys - Thr - Val - Tyr - Trp - Asp - Arg - Asp - Met. Comparison of the sequence of murine beta 2-microglobulin to the sequences reported for the homologues from man, rabbit, and guinea pig indicate identities of 68%, 66%, and 61%, respectively.

Primary structure of murine major histocompatibility alloantigens: amino acid sequence of the cyanogen bromide fragment Ia (positions 139-228) from the H-2Kb molecule

The complete amino acid sequence of the cyanogen bromide (CNBr) fragment Ia (CN-Ia) from the murine histocompatibility antigen H-2Kb has been obtained by using radiosequence methodology. This glycopeptide is the largest CNBr cleavage product of the H-2K molecule and extends from position 139 to position 228. The sequence determined for CN-Ia was Ala-Ala-Leu-Ile-Thr-Lys-His-Lys-Trp-Glu-Gln-Ala-Gly-Glu-Ala-Glu-Arg-Leu-Arg-Ala -Tyr-Leu-Glu-Gly-Thr-Cys-Val-Glu-Trp-Leu-Arg-Arg-Tyr-Leu-Lys-Ans-Gly-(Asn)-Ala- Thr-Leu-Leu-Arg-Thr-Asp-Ser-Pro-Lys-Ala-His-Val-Thr-His-His-Ser-Arg-Pro-Asp-Asp -Lys-Val-Thr-Leu-Arg-Cys-Trp-Ala-Leu-Gly-Phe-Tyr-Pro-Ala-Asp-Ile-Thr-Leu-Thr-Tr p-Gln-Leu-Asn-Gly-Glu-Glu-Leu-Ile-Gln-Aps-Met. The data were obtained by analysis of fragments derived by thrombic, tryptic, chymotryptic, and V8 protease digestion of CN-Ia. A carbohydrate moiety is attached to Asn at position 176. Homology between this 90 amino acid stretch of H-2Kb and HLA-B7 [Orr, H. T., Lopez de Castro, J. A., Lancer, D., & Strominger, J. L. (1979) Biochemistry 18, 5711] is 68%, and differences are noted at positions 176, 177, and 178 which in the H-2 molecule are the attachment region for a second carbohydrate moiety. No carbohydrate was detected in this position for HLA-B7 [Orr, H. T. Lopez de Castro, J. A. Lancet, D., & Strominger, J. L. (1979) Biochemistry 18, 5711].

Primary structure of murine major histocompatibility complex alloantigens: completion of the sequence of the amino-terminal 284 residues of H-2Kb

The primary structure of the COOH-terminal cyanogen bromide (CNBr) cleavage fragment Ic (CN-Ic) of the extracellular portion of the murine histocompatibility antigen H-2Kb has been completed. CN-Ic contains a site of papain cleavage which has been utilized for solubilizing H-2Kb by cleaving off the membrane integrating portion of the molecule. The amino acid sequence of CN-Ic has been determined by using peptides recovered after trypsin digestion of CN-Ic before and after blockage of lysine groups with citraconic anhydride. Overlapping sequences for the tryptic fragments were obtained by amino-terminal sequence analysis. The sequence of fragment CN-Ic, which spans residues 229-284 in H-2Kb, is as follows: Glu-Leu-Val-Glu-Thr-Arg-Pro-Ala-Gly-Asp-Gly-Thr-Phe-Gln-Lys-Trp-Ala-Ser-Val-Val-Pro-Leu-Gly-Lys-Glu-Gln-Tyr-Tyr-Thr-Cys-His-Val-Tyr-Gln-Gln-Gly-Leu-Pro-Gln-Pro-Leu-Thr-Leu-Arg-Trp-Asp-Glu-Pro-Pro-Ser-Thr-Val-Ser-Asn-Met. This amino acid sequence determination completes the primary structure of the amino terminal 284 residues of H-2Kb, that portion of this histocompatibility antigen which is external to the cell membrane and which contains antigenic determinants. It was also possible to identify Val-281 as a papain cleavage site within CN-Ic. The completed structure was analyzed solely by radiochemical methods. The structure obtained for H-2Kb is 71% homologous to the reported structure of HLA-B7, a human homologue.

Biochemical studies on the H-2K antigens of the MHC mutants bm3 and bm11

Biochemical analyses of the H-2K-gene products of the C57BL/6 mutant strains, bm3 and bm11, have been carried out in order to characterize the structural relationships among these antigens. From comparative tryptic peptide mapping of cyanogen bromide fragments from the mutant and parent Kb glycoproteins and from preliminary amino-acid sequence analyses, a number of discrete differences have been discerned. Two sites of difference at amino residues 77 and 89 in the Kbm3 glycoprotein are noted relative to Kb. An alteration at residue 77 similar or identical to that seen in Kbm3 is present in the K antigen of the bm11 mutant. Because our techniques sample only 75 to 80 percent of the extracellular portion of H-2Kb, other undetected changes are possible. However, our present findings are most consistent with the conclusion that only very limited differences exist between mutant and parent molecules. Further, taken together with CML (cell-mediated-lymphocytotoxicity) reaction patterns (Melief et al. 1980), the biochemical data support the hypothesis that the proposed structural alterations in the Kb mutant glycoproteins are directly related to their observed immunological specificity.

Role of self and foreign antigenic determinants in allogeneic and self-restricted cytotoxic T cell recognition

Murine spleen cells were sensitized in vitro to H-2 disparate allogeneic spleen cells and assayed on syngeneic target cells conjugated with the trinitrophenyl (TNP)-self or the fluorescein isothiocyanate (FITC)-self haptens, or on syngeneic target cells expressing the male H-Y antigen (H-Y self). The results indicated that allo-induced cytotoxic T lymphocytes (CTL) contained effectors that lysed both hapten-self but not H-Y self targets. Furthermore, it was demonstrated that separate populations of those allogeneic CTL were responsible for the lysis of TNP-self and FITC-self targets. This study also showed that cytotoxic effectors generated against the H-Y antigen with lytic activity equal to or greater than that of an allogeneically induced CTL response were unable to lyse hapten-self targets. These findings provide the first evidence that H-2 alloantigens may be unique in their ability to induce effectors that lyse hapten-conjugated autologous targets. These observations are discussed with respect to the self and foreign antigenic determinants involved in allogeneic and self-restricted CTL models.

The genome-linked protein of picornaviruses. VII. Genetic mapping of poliovirus VPg by protein and RNA sequence studies

The poliovirus genome-linked protein (VPg) has been subjected to radiochemical microsequence analysis. Sequence studies of virion RNA by a modification of Sanger's dideoxy method have revealed a base sequence corresponding to the amino acid analysis. This result proves that VPg is virus-encoded. The RNA sequence has allowed us to predict the total amino acid sequence of VPg and part of its precursor. VPg is, at most, 27 amino acids long. It maps within the 3' terminal segment of the viral genome that encodes the precursor polypeptide NCVP1b for the virus-specific RNA polymerase NCVP4.

Structure of the heavy chain of the H-2Kk histocompatibility antigen

We have used radiochemical techniques to characterize the heavy chain (Mr 46,000) of the murine H-2Kk histocompatibility antigen in terms of six fragments (I-VI) obtained after cleavage of the polypeptide chain with CNBr. The tentative order of the fragments, which account for more than 90% of the heavy chain, was assigned by radiochemical sequence analysis of the intact heavy chain and of each purified CNBr fragment and by analysis of the CNBr fragments obtained from the large papain fragment of the heavy chain. Treatment of cells with tunicamycin yielded H-2 molecules with heavy chains of molecular weight 40,000, suggesting that the carbohydrate moieties have a combined molecular weight of approximately 6000. CNBr cleavage of H-2Kk heavy chains labeled with [3H]fucose indicated that the carbohydrate moieties are located on fragments II and IV.. Incubation of cells with 32PO4 gave H-2 molecules with radioactive phosphoserine in the carboxyl-terminal CNBr fragment (VI) of the heavy chain and in the fraction containing beta 2-microglobulin. Sequence analysis of each CNBr fragment intrinsically labeled with 3H- and 35S-labeled amino acids identified a total of 87 residues in the H-2Kk heavy chain. The sequence closely resembles that of the H-2Kb molecule, and the 11 differences are scattered throughout the polypeptide chain. Comparison with HLA sequences indicates that the two allelic H-2 sequences are more closely related to each other (88% identity) than either is to the HLA-B7 or A2 antigens (approximately 70%). Similarly, the nonallelic HLA antigens are more closely related to each other (83%) than either is to the H-2Kk or H-2Kb molecules.

Isolation, characterization and amino acid sequence studies of the cyanogen bromide fragments of the H-2Dd glycoprotein

The papain-solubilized fragment of the H-2Dd antigen, representing the NH2-terminal 80% of the native glycoprotein, can be fragmented into five polypeptides using CNBr cleavage. These fragments have been isolated, characterized and subjected to amino acid sequence analysis using radiochemical microtechniques. It was possible to align these CNBr fragments by comparison of their NH2-terminal amino acid sequence with the known amino acid sequence of the H-2Kb molecule. Thus, the NH2-terminal fragment, D, contains 23 residues and is followed by a glycopeptide, fragment C, of 75 residues. Following fragment C are three fragments held together by disulfide bonds: fragment b4, which has 40 amino acid residues, a second glycopeptide, fragment b2, of 90 residues, and fragment b3, a peptide of approximately 55 residues which terminates at the site of papain cleavage. The complete amino acid sequence of the NH2-terminal CNBr fragment, D, has been determined, and this is presented here along with sequence data for the NH2-terminal 30 residues of each of the other four CNBr fragments of the papain fragment of H-2Dd. A total of 146 positions have been examined in the approximately 280-residue H-2Ddpapain molecule, and a total of 127 residues have been positively determined. Most of the unassigned positions may be tentatively assigned as Asp or Asn, the only amino acids so far not incorporated in radiolabeled form by our metabolic labeling procedures into the H-2Dd molecule. Comparison of the sequence data obtained for the H-2Dd molecule to data available for other histocompatibility antigens revealed homologies of approximately 90% with H-2Kb and H-2Ld, and approximately 75% with HLA-B7 and HLA-A2.

Comparison of alloantisera and hybridoma antibody for purification of the H-2Db murine histocompatibility antigen and preliminary molecular characterization of this antigen

Previous studies on the determination of the complete amino acid sequence of H-2 molecules have relied on alloantisera to purify the H-2 molecules by immunoprecipitation. In this study, directed toward the determination of the complete amino acid sequence of the H-2Db molecule, it was found that all H-2.2 alloantisera examined had very low antibody titers when analyzed by immunoprecipitation and that most of these antisera reacted with not only the H-2Db heavy chain but also with a 75,000 dalton virus-associated glycoprotein (gp 75). The problems encountered with conventional alloantisera were surmounted by utilizing a monoclonal antibody from hybridoma B22-249R1 obtained as described by Hämmerling et al. (1979) and maintained in ascites form in (CBA x Balb/c) F1 mice. This antibody reacted with only 45,000 molecular weight material and had the added advantage of requiring only 0.1 ml of hybridoma ascites fluid to bind all of the H-2Db antigen from 3 x 10(8) EK-4 tumor cells. Biochemical examination of the purified H-2Db molecule showed that it possessed overall structural properties similar to other previously characterized H-2 molecules. An NH2-terminal amino acid sequence was determined for the H-2Db molecule for 28 residues and this sequence was compared to the complete NH2-terminal sequences of the H-2Kb and H-2Dd molecules, and the partial NH2-terminal sequence for the H-2Ld molecule; these comparisons indicated 82%, 75% and 100% homology respectively. In addition, these preliminary studies indicated that there was little or no beta-2-microglobulin (beta 2 mu) in the immunoprecipitates with the H2-2Db heavy chain. This lack of beta 2 mu in the immunoprecipitates was found to be true for alloantisera directed against private or public specificities, a xenoantiserum (sheep anti-H-2b), or hybridoma antibody used in the immunoprecipitation.