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N Koch

Publications and source records attributed to N Koch.

At least 73 records · Page 4Linked to original sources
PubMed1986

The assignment of chain specificities for anti-Ia monoclonal antibodies using L cell transfectants.

The chain specificities of 18 Ak and 26 Ab-reactive anti-Ia monoclonal antibodies have been determined. L cells were transfected with haplotype-matched (A alpha k:A beta k, A alpha b:A beta k) or haplotype-mismatched (A alpha k:A beta b, A alpha b:A beta k) cDNA pairs, lines expressing high levels of surface A complex were selected, and antibody reactivity with a panel of reagents was assessed by cytofluorimetric analysis. Most of the antibodies recognized a determinant specified by one chain, either alpha or (more commonly) beta. A few examples of more complex determinants were also observed. A knowledge of the chain specificities of anti-Ia monoclonal antibodies should prove useful for a variety of studies aimed at dissecting Ia structure-function relationships.

Animals↗
PubMed1986

The HLA-D-associated invariant chain binds palmitic acid at the cysteine adjacent to the membrane segment.

The highly polymorphic HLA-D antigens are associated with a nonpolymorphic polypeptide chain, designated invariant chain. This invariant chain is shown to incorporate fatty acid. Invariant chain metabolically labeled with [3H]palmitic acid releases its label after treatment with hydroxylamine indicating an ester linkage of the palmitic acid. The binding of fatty acid to the invariant chain inhibits the formation of S-S-linked dimers. This suggests that the sole cysteine residue of the invariant chain is blocked by binding of fatty acid. A peptide shared by [3H]palmitic acid- or [35S]cysteine-labeled invariant chain digests supports the hypothesis that the palmitic acid binds to the cysteine which is located close to the membrane-spanning domain on the cytoplasmic site. Inhibition of N-glycosylation with tunicamycin demonstrates binding of the fatty acid to the nonglycosylated precursor of the invariant chain. Additionally, blocking of fatty acylation by cerulenin inhibits further maturation of the invariant chain, as sialylation.

Antibodies, Monoclonal↗
PubMed1986

Differential expression of Ia and Ia-associated invariant chain in mouse tissues after in vivo treatment with IFN-gamma.

B10.BR mice were injected i.v. with varying doses of recombinant IFN-gamma on three consecutive days. In tissue sections of 13 organs, the distribution of Ia antigens and Ia-associated invariant chain (Ii) was studied by using an immunoperoxidase technique. In the control animal, Ia and Ii were shown to be co-expressed in most tissues. However, on Kupffer cells, a small number of hepatocytes, and a subset of lymphocytes in lymph nodes and in the splenic red pulp only Ii, and no Ia, was detectable. In contrast, strongly Ia+ interdigitating reticulum cells of T-dependent areas of lymph nodes and spleen were only weakly stained for Ii. IFN-gamma treatment resulted in a dramatic increase of MHC antigen expression throughout the body, with striking differences in the inducibility of certain tissues for Ia and Ii: Bronchial epithelium was clearly induced to express the invariant chain, whereas Ia antigens remained entirely absent. Moreover, in kidney tubules and colon epithelium, Ii was induced more broadly than Ia. In contrast to the induction of Ii on endothelial cells of larger vessels in kidney, heart, and lungs, no de novo expression of Ia or Ii in capillary endothelial cells was observed. The number of detectable Ia+/Ii+ interstitial dendritic cells considerably increased upon exposure to IFN-gamma. Neither neurons nor glial cells were induced to MHC antigen expression. Our data demonstrate that IFN-gamma applied i.v. is a potent inducer or enhancer of Ia antigens and invariant chain in a variety of cell types.

Animals↗
PubMed1986

In vivo induction of H-2K/D antigens by recombinant interferon-gamma.

B10.BR mice received i.v. increasing doses of recombinant interferon-gamma (rIFN-gamma) on three consecutive days. Using an immunoperoxidase technique the distribution of H-2K/D antigens was studied in frozen tissue sections of thirteen organs (kidney, liver, pancreas, esophagus, stomach, small intestine, colon, lungs, heart, brain, thymus, lymph node and spleen). Class I antigens were shown to be induced or enhanced in almost every organ after exposure to IFN-gamma. This effect was particularly conspicuous for renal tubular cells, hepatocytes, bronchiolar epithelial cells, gastric mucous cells, thymic cortical lymphocytes and capillary endothelial cells in heart and kidney. Neurons, glial cells, gastric chief and parietal cells, and pancreas cells were not inducible. The findings show that i.v. application of IFN-gamma leads to strong induction or enhancement of major histocompatibility complex class I antigens in a wide variety of tissues.

Antibodies, Monoclonal↗
PubMed1985

Ia-associated invariant chain is fatty acylated before addition of sialic acid.

The murine invariant chain (Ii) was found to incorporate radioactive palmitic acid. This binding of fatty acid inhibits the formation of interchain S-S bonds, probably because the cysteine residue in the transmembrane region of the Ii chain is palmitylated. The inhibition of fatty acylation by cerulenin blocks further posttranslational maturation of the invariant chain as shown by two-dimensional gel electrophoresis of Ii immunoprecipitates. In particular, the addition of sialic acid residues is blocked. Thus, it appears that fatty acylation is essential for carbohydrate processing of the Ii chain.

Acylation↗
PubMed1985

The gene encoding the Ia-associated invariant chain is located on chromosome 18 in the mouse.

The chromosomal assignment of the gene encoding the invariant (Ii) chain associated with the mouse immune response antigens (Ia) was determined by Southern blot analysis of DNA from a panel of mouse X Chinese hamster somatic cell hybrids cleaved with Hind III or Eco RI. Using a mouse li cDNA as a hybridization probe, we localized the gene coding for the invariant chain to mouse chromosome 18.

Animals↗
PubMed1985

Expression of Ia antigens in a murine T-lymphoma variant.

ESb, a cellular high metastatic variant derived from the murine T-cell lymphoma L5178Y (Eb), was found to synthesize Ia antigens. Ia-specific antibodies reacted with the ESb cells and precipitated Ia-like molecules from them. Two-dimensional gel electrophoretic analysis of immunoprecipitates of metabolically labeled ESb cells indicated that the Ia molecules on ESb were indistinguishable from those on murine B-cells. No Ia antigens were detectable on the parental tumor line Eb. Treatment with recombinant interferon-gamma (IFN-gamma) caused enhancement of class I histocompatibility antigen expression on Eb and ESb tumor lines. In ESb cells the expression of Ia and of Ia-associated invariant chain (Ii) was also increased upon IFN-gamma treatment. No induction of either Ia and Ii antigens was observed upon IFN-gamma treatment of the Eb line. These studies demonstrate a substantial difference between the Eb and ESb tumor lines with respect to: (i) constitutive expression of class II major histocompatibility antigens, and (ii) response to IFN-gamma treatment.

Animals↗
PubMed1985

Plasma cell antigen PC-1 and the transferrin receptor in mouse, rat, and hamster: serologic and biochemical analysis.

The plasma cell membrane antigen PC-1 and the receptor for the iron transport protein transferrin are high m.w., developmentally regulated proteins consisting of two similar or identical disulfide-bonded subunits. In this paper, we report the results of a serologic and biochemical analysis of these proteins in various strains of inbred mice, and in rats and hamsters. A monoclonal antibody against the PC-1a allelic product is shown to detect an antigenic determinant on the PC-1 molecule that has the same strain distribution as the antigen previously detected with polyclonal alloantisera. The mouse PC-1 protein was purified from plasma cells of the PC-1a genotype and was used to generate polyclonal rabbit anti-PC-1 antibodies. These antibodies precipitated a homologous protein from plasmacytoma cells derived from PC-1- congenic mice, demonstrating that PC-1b is not a "null" allele. The PC-1b allelic product had a slightly lower apparent m.w. than the PC-1a product, and had a slightly more basic isoelectric point. Rabbit anti-mouse PC-1 antibodies also precipitated a homologous protein from immunoglobulin-secreting cells of rat and hamster origin, but did not show detectable cross-reaction with the transferrin receptor. Disulfide bonding between chains was conserved in both PC-1 and the transferrin receptor in all species examined, but transferrin receptors from mouse cells had a significantly higher apparent m.w. than those of rat, hamster, or human cells.

Animals↗
PubMed1985

One gene encodes two distinct Ia-associated invariant chains.

Murine immune response region-encoded Ia antigens are associated not only with invariant (Ii) chain but also with several other polypeptides, most notably a 41K protein. The present report demonstrates a striking similarity between Ii and 41K. These polypeptides were found to be serologically cross-reactive, and they also display a similar peptide composition on partial enzymatic digestion. Both polypeptides are derived from distinct unglycosylated precursors, as demonstrated by tunicamycin treatment and cellfree translation. Hybrid selection of mRNA, as well as Northern blotting with an Ii cDNA, shows the presence of two mRNA coding for the Ii chain and the 41K protein. Rat fibroblasts transfected with a mouse genomic Ii clone synthesize both the murine Ii chain and the 41K protein. These observations demonstrate that a single Ii gene encodes two distinct but closely related proteins.

Animals↗
PubMed1984

Structure of the murine Ia-associated invariant (Ii) chain as deduced from a cDNA clone.

The invariant (Ii) chain is a membrane-spanning glycoprotein found intracellularly associated with class II major histocompatibility complex (MHC) molecules. Using hybrid-selected translation and the Ii-specific monoclonal antibody In-1, we have isolated a cDNA clone (pIi-5) coding for most of the Ii chain. Sequence analysis of this clone reveals an open reading frame encoding 169 amino acid residues. The protein is rich in methionine and contains two potential N-glycosylation sites. No stretch of uncharged amino acid residues, characteristic for a membrane-spanning segment, is found close to the COOH-terminal end. There is one, however, close to the NH2-terminal end. As it is know that approximately 20 amino acid residues of Ii chain are exposed on the cytoplasmic side, we conclude that the Ii chain spans the membrane exposing the NH2 terminus on the cytoplasmic side and the COOH terminus on the luminal side.

Amino Acid Sequence↗
PubMed1984

Monoclonal antibodies detect polymorphic determinants shared by I-A and I-E antigens.

Binding data on inbred mouse strains and immunochemical isolation of Ia antigens with subsequent separation on non-reduced/reduced two-dimensional gels provide evidence for the cross-reactivity of monoclonal antibodies with I-A and I-E products. Thus two monoclonal antibodies were found to react with A alpha A beta as well as E alpha E beta dimers. One of these mAbs, K22 -42, reacts with the precursor form of E beta chain of B10.GD mice which is associated with the invariant chain (Ii). This indicates that the respective determinant on E beta is formed prior to association of E beta with E alpha.

Animals↗
PubMed1984

Differential expression of the invariant chain in mouse tumor cells: relationship to B lymphoid development.

We have examined 25 cultured lines of mouse tumor cells for synthesis of the Ii, an Ia-associated polypeptide, by using an anti-Ii monoclonal antibody. Six of the T lymphomas tested did not produce detectable levels of Ii or of surface Ia antigens. Three B lymphomas and two plasmacytomas that express surface Ia antigens were found to synthesize the Ii. In addition, Ii was immunoprecipitated from two of five Ia- pre-B lymphomas, two of four Ia- plasmacytomas, two Ia- myeloid tumors, and two fibroblast cell lines including LM(TK-). Because Ia antigens have so far been found only on cells that also synthesize Ii, we suggest that the Ii is a marker of those cells that in certain states of development or activation express Ia antigens.

Animals↗
PubMed1984

Ia antigens and associated invariant chain are induced simultaneously in lines of T-dependent mast cells by recombinant interferon-gamma.

Metabolic labeling and immunoprecipitation with monoclonal antibodies, showed that lines of T-dependent mast cells (P cells) that were cultured in the absence of interferon-gamma (IFN-gamma) did not synthesize detectable amounts of Ia antigens or the invariant chain (Ii). After exposure for 24 hr to IFN-gamma produced from the cloned Mu IFN-gamma gene, P cells synthesized large amounts of Ia alpha- and beta-chains and of the invariant chain. The I-A and I-E antigens of these T-dependent mast cells were indistinguishable from those of B cells in terms of the binding of a panel of monoclonal antibodies and in terms of their structure and that of associated molecules as analyzed in two-dimensional gels. The effect of IFN-gamma on Ii synthesis in P cells was not due merely to inhibition of proliferation, as is the case with certain B cell lines, because treatment of P cells with mitomycin C did not induce the invariant chain. Variant lines of P cells that did not respond to IFN-gamma with the synthesis of Ia antigens, but only the enhanced expression of H-2K, H-2D, and H-2L antigens, also failed to synthesize Ii chain. Experiments using three tumor lines related to B lymphocytes, however, indicated that in these cells IFN-gamma could enhance the synthesis of Ii in the absence of Ia antigens. Whereas Ii chain may be essential for Ia expression, Ii chain may have further functions and in some lines can be regulated independently by IFN-gamma in the absence of Ia antigen expression.

Animals↗
PubMed1983

Regulation of MHC class II invariant chain expression: induction of synthesis in human and murine plasmocytoma cells by arresting replication.

The expression of the H2 Ia-associated invariant chain (Ii) has been determined by pulse labeling cells with [35S]methionine and resolving the proteins. Expression is maximal in noncycling peripheral B lymphocytes and is reduced upon maturation of B lymphocytes to plasma cells. B cell-derived cell lines behave correspondingly: IgM+ non-secretor cell lines synthesize Ii while plasmocytoma cells do not. Pre-B cell lines are also negative. In all Ii-negative cell lines, the synthesis of Ii is selectively induced by treating the cells with inhibitors of replication.

Animals↗
PubMed1983

Structural comparison of I-A antigens produced by a cloned murine T suppressor cell line with B-cell-derived I-A.

A cloned, antigen-specific T suppressor cell line derived from a CBA mouse expresses large amounts of I-A and I-E antigens. Comparative two-dimensional polyacrylamid gel electrophoresis of biosynthetically labeled I-A antigens immunoprecipitated with a variety of monoclonal I-Ak-specific antibodies suggested that alpha, beta and Ii polypeptide chains are identical with B-cell-derived I-A. Dimeric complexes formed by I-A chains derived from B or T suppressor cells were also similar with two major exceptions. Pulse-labeled T-cell-derived Ia antigen was complexed with two additional unknown components of about 31K. These components were not visible in pulse-chased (processed) materials. In addition, T suppressor-cell-derived I-A antigens did not contain S-S linked dimers consisting of processed alpha and beta chains, which are usually formed during solubilization of B cells. We consider the possibility that in T cells these chains are associated with other structures, thus preventing S-S linkage between alpha and beta chains.

Animals↗