SOME BIOCHEMICAL PROPERTIES OF THYMUS LEUKEMIA ANTIGENS SOLUBILIZED FROM CELL MEMBRANES BY PAPAIN DIGESTION

Thymus leukemia (TL) alloantigenic activity was solubilized by papain proteolytic digestion from intact RADA1 tumor cells. If the cells were labeled with amino acids and fucose, the TL alloantigen could be isolated as a doubly labeled glycoprotein fragment by indirect precipitation from the papain digest. This TL glycoprotein fragment was approximately the same mol wt as the papain-digested H-2.4 alloantigen fragment as judged by chromatography on Sephadex G-150 in sodium dodecyl sulfate. The carbohydrate chain of the TL glycoprotein obtained by exhaustive pronase digestion behaved as a glycopeptide of approximately 4,500 mol wt, as compared with the glycopeptide of the H-2.4 alloantigen that had a mol wt of about 3,500. Thus, the TL alloantigen can be solubilized by papain digestion as a glycoprotein fragment similar in mol wt to the H-2 alloantigen glycoprotein fragment. The carbohydrate chain of the TL glycoprotein is larger than the H-2 carbohydrate chain

Functional Classification of Immune Regulatory Proteins

SummaryThe members of the immunoglobulin superfamily (IgSF) control innate and adaptive immunity and are prime targets for the treatment of autoimmune diseases, infectious diseases, and malignancies. We describe a computational method, termed the Brotherhood algorithm, which utilizes intermediate sequence information to classify proteins into functionally related families. This approach identifies functional relationships within the IgSF and predicts additional receptor-ligand interactions. As a specific example, we examine the nectin/nectin-like family of cell adhesion and signaling proteins and propose receptor-ligand interactions within this family. Guided by the Brotherhood approach, we present the high-resolution structural characterization of a homophilic interaction involving the class-I MHC-restricted T-cell-associated molecule, which we now classify as a nectin-like family member. The Brotherhood algorithm is likely to have a significant impact on structural immunology by identifying those proteins and complexes for which structural characterization will be particularly informative

Unexpected complexity of the dm1 mutation revealed in the structure of three H-2D/L-related antigens

The H-2L dm1 and H-2D dm1 MHC antigens of the B10.D2 ( H-2 dm1 ) mutant mouse strain (formerly known as M504 or H-2 da ) have been compared to the H-2L d and H-2D d antigens of the B10.D2 ( H-2 d ) mouse strain. L dm1 and L d are 45 000 M r antigens and both are reactive with anti-H-2.“28” ( k/r anti- h2 ) serum and unreactive with anti-H-2.4 ( k/b anti- a ) serum which detects private determinants of the D dm1 and D d antigens. However, the tryptic peptide compositions of these two antigens are different and, based on the number of major tryptic peptides which coelute during ion-exchange chromatography, the estimated peptide homology between L dm1 and L d is 80 percent. A newly defined antigen (M r = 39 000), designated gp39 dm1 , was found in glycoprotein extracts of the dm1 strain but not of the d strain. This antigen coprecipitates with L dm1 but does not coprecipitate with D dm1 indicating that it lacks the H-2.4 determinant. In comparison with L dm1 , gp39 dm1 appears to contain far fewer Arg and Lys residues and is most likely not a simple proteolytic fragment of L dm1 . Finally, peptide maps of the D dm1 antigen show that the majority of its Arg peptides are identical to D d Arg peptides, whereas at least five of its Lys peptides and three of its Arg peptides correspond not to D d peptides but to L d and L dm1 peptides. These data raise the possibility that the D dm1 antigen is a hybrid molecule and they have also revealed an unexpected level of complexity in the dm1 mutant phenotype.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46737/1/251_2004_Article_BF00364331.pd

COMPARISON OF SOLUBLE HUMAN AND MOUSE TRANSPLANTATION ANTIGENS

The molecular and chemical characteristics of membrane components bearing the major transplantation antigen systems in mouse (H-2) and man (HL-A) were compared and found to be strikingly similar. Kinetics of papain solubilization from cell membranes, gel filtration, and electrophoretic patterns of the alloantigenic components were found to be nearly identical. Comparable size heterogeneity of the solubilized materials was also demonstrated. Some differences in amino acid and carbohydrate content of the purified H-2 and HL-A alloantigenic materials were found. The general pattern of distribution of the amino acid residues, however, appears to be quite similar and indicate compositional relatedness in these materials. These physical and chemical similarities in the characteristics of molecules bearing the transplantation antigens are in accord with biologic studies indicating a comparable functional immunologic role for the mouse H-2 and human HL-A antigen systems. These studies support the view that the genes determining these major transplantation antigen systems may have evolved from a common precursor

Cell Surface Antigen Induced by Friend Murine Leukemia Virus Is also in the Virion

Intact particles of Friend leukemia virus derived from infectious mouse serum absorb only trace amounts of cytotoxic anti-FMR antibodies, but physical disruption of the virions by freezing and thawing, by ether extraction or by detergent treatment releases large amounts of FMR antigenic activity. Thus this antigen, previously considered to occur mainly as a neo-antigen on the surfaces of virus-infected cells and as a soluble substance in the serum of infected mice, may be primarily a virion component

Comparison of the Peptide Composition of Two Histocompatibility-2 Alloantigens

The peptide composition of purified Histocompatibility-2 (H-2) reactive glycoprotein fragments from two murine strains allelic at the H-2 locus (H-2(b) and H-2(d)) were compared by a cellulose thin-layer peptide mapping micro technique. Approximately 70 per cent of the theoretical maximum number of peptides produced by cyanogen bromide cleavage and trypsin digestion were visualized by this technique. Most (38) of the peptides for the glycoproteins from these strains allelic for the H-2 locus were identical; however, three peptides of the H-2(b) and four peptides of the H-2(d) alloantigen were unique. The results demonstrate the remarkable similarity in protein structure between these two allelic products, but also show a small but reproducible difference in their peptide composition. The findings are consistent with the hypothesis that protein primary structure may determine wholly or in part their alloantigenic activities

The Molecular Basis of Codominant Expression of the Histocompatibility-2 Genetic Region

H-2 alloantigens in an intact, undegraded form can be solubilized by the nonionic detergent NP-40 and isolated by indirect immunoprecipitation and electrophoresis in sodium dodecyl sulfate on polyacrylamide gels. With the use of an immunological precipitation method, the question about the number of cellular H-2 gene products in heterozygous cells has been partially resolved. At least four separable gene products were detected in cells heterozygous at the H-2 genetic region—one for each of the H-2D genes of the two parental haplotypes, and one for each of the H-2K genes of the two parental haplotypes. This is in contrast to the two H-2 gene products reported previously for cells homozygous at the H-2 region. The findings establish that the two parental H-2 haplotypes on homologous chromosomes in heterozygous cells are ultimately expressed as different glycoprotein molecules