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M Simonsen

Publications and source records attributed to M Simonsen.

At least 37 records · Page 2Linked to original sources
PubMed1986

Isolation and characterization of chicken and turkey beta 2-microglobulin.

Chicken and turkey beta 2-m were isolated from citrated plasma in sequential use of three chromatographic steps: affinity chromatography, gel filtration chromatography and anion-exchange chromatography. The purified protein was identified as beta 2-m by reaction with a beta 2-m specific monoclonal antibody and by the ability to recombine with the chicken MHC class I heavy chain. The purity was estimated by SDS-PAGE and IEF. The pI was between 5.1 and 5.3 for chicken beta 2-m and 4.7 and 4.8 for turkey beta 2-m, which fact is reflected in their different electrophoretic mobilities in agarose gel (turkey migrates in the alpha and chicken migrates in the beta region). The mol. wt of both chicken and turkey beta 2-m was 14,500 estimated by SDS-PAGE whereas calculations based on the amino acid compositions gave mol. wts of 11,000. EM280 was 15.9 for chicken beta 2-m and 16.4 for turkey beta 2-m. The amino acid compositions and sequences of the two avian beta 2-m molecules have been compared with earlier data from the literature. The sequence of the 23 N-terminal amino acids was found to be identical in our preparations from both chicken and turkey, namely DLTPKVQVYSRFPASAGTKNVLN, and is incompatible with a previously published sequence also thought to be from turkey beta 2-m. Reasons for our opinion that the molecules isolated and sequenced in this paper are the correct ones are given.

Amino Acid Sequence↗
PubMed1986

The major histocompatibility complex class I heavy chain as a structural subunit of the human cell membrane insulin receptor: implications for the range of biological functions of histocompatibility antigens.

Monoclonal antibodies against some of the monomorphic determinants of major histocompatibility complex (MHC) class I molecules reduce insulin binding and precipitate 125I-labeled insulin receptor preparations. A monoclonal antibody with specificity for the insulin binding site on the cell membrane insulin receptor of human cells was used to precipitate insulin receptors from human cell lines and resulted in distinct bands of Mr approximately 130,000, 90,000, and 45,000. The Mr 45,000 molecules thus precipitated were subjected to NaDodSO4/PAGE, eluted from the gels, and found to react with monoclonal antibodies against monomorphic and a polymorphic MHC class I determinant known to be expressed on the cell line used as receptor source. Moreover, a murine thymoma line (RI) with MHC class I expression bound significant amounts of insulin, whereas a MHC class I-negative variant had low insulin binding capacity. Reduction in the density on human cells of the MHC class I heavy chain was obtained by capping with antibodies to beta 2-microglobulin or to the MHC class I heavy chain and resulted in decreased insulin binding, whereas down-regulation of insulin receptors induced increased density of MHC class I molecules. It is concluded that the MHC class I heavy chain and the tetrameric insulin receptor are structurally associated in the cell membrane and suggested that this association may occur by displacement of beta 2-microglobulin by the insulin receptor.

Antibodies, Monoclonal↗
PubMed1985

Analysis of chickens for recombination within the MHC (B-complex).

In an attempt to further map the chicken MHC (the B complex), a systematic search for genetic recombinants within the B complex was performed by serotyping the progeny from F2 crosses of chickens by means of specific anti-class I, anti-class II, and anti-class IV alloantisera. Two recombinant B-haplotypes (B21r and B15r) were found by analysing 2,656 F2 chickens representing 5,312 informative typings. In either case, the B-G (class IV) allele was recombined with both the B-F and B-L alleles of the opposite haplotype. MLC typings, tests for direct compatibility by GVH reactions, and absorption analyses confirmed the original serological typing of the two recombinant B haplotypes. No recombination between B-F (class I) and B-L (class II) loci was found. This very low frequency of recombination within the B complex as compared with recombination frequencies found in mammalian MHC's is discussed.

Animals↗
PubMed1985

The physiology of the major histocompatibility complex.

The term compound receptors (C.R.) is used here to describe reversible molecular complexes in the cell membrane which attain their final biologically active structure by rearrangement and assembly of several structural subunits. The C.R. to be discussed involve the participation of the glycoproteins belonging to the major histocompatibility complex (MHC), notably of class I molecules which are themselves reversible compounds of a heavy chain and a light chain (beta 2-m). The main thesis of this discussion is the postulate that the fundamental immunological phenomenon known as MHC restriction is due to the formation in the membrane of reversible C.R. with additional roles in the physiology of the cell. The interaction between MHC class I molecules and insulin receptor molecules will be mentioned as an illustration of the general hypothesis.

Animals↗
PubMed1982

The MHC haplotypes of the chicken.

The major histocompatibility complex (MHC) of Gallus gallus is the B complex of which three classes of cell-membrane antigens have been clearly defined by serological, histogenetic, and biochemical methods. Two of these classes are homologous to classes I and II of mammals (B-F and B-L, respectively), while the third (B-G) is a differentiation antigen of the erythroid cell-line; the mammalian homologue of this class is still undefined. The B haplotypes comprise at least one gene of each class that displays linkage disequilibrium of a remarkable strength. The present work is the first systematic comparison by serological and histogenetic methods of the allelic products (allomorphs) of 15 haplotypes, including all of the 11 that were accepted as "standard" B haplotypes at the recent international Workshop on the chicken MHC in Innsbruck, Austria. The analysis has revealed many similarities, but only four pairs of probable identities: G2 and G12, F4 and F13, L4 and L13, L12 and L19. It appears therefore that the B-G locus is comparable in its degree of polymorphism to the class I (B-F) locus. The "standard" haplotypes are almost all of White Leghorn derivation, and preliminary typings of other breeds of chickens, and of wild chickens, indicate the existence of a much wider spectrum of allomorphs.

Alleles↗
PubMed1982

Complement mediated lysis in chickens.

Rat erythrocytes, when either injected i.v. into chickens, or incubated in vitro with chicken serum, will be lysed within minutes. This lysis is complement dependent but does not involve specific antibodies since Ig-free bursectomized chickens behave in exactly the same way as normal chickens with high levels of haemagglutinating antibodies. The lysis is mediated by activation of complement component C3 via the alternative complement pathway and various observations lead us to doubt the functional existence in this lytic reaction of the classical complement pathway.

Animals↗
PubMed1982

The major histocompatibility complex of outbred chickens. I. Analysis of the B13 haplotype by serology and cellular reactions.

The F antigens, which are serologically defined Class I gene products of the major histocompatibility complex in chickens (the B complex), were analysed in outbred birds. Private specificities of the F13 antigen from the inbred CC strain were detected in 20 outbred chickens by a haemagglutination technique. In the GVH-inhibition-release test F13 antigens from outbred and inbred chickens were identical. The L antigens, which are the Class II antigens of the B complex, were detected with specific anti L13 alloantisera by indirect immunofluorescence. Antisera defining the L13 antigen(s) of the inbred CC line reacted with all F13 positive outbreds. As a test of one-way direct compatibility of the inbred and outbred animals typing F13, graft versus host reactions were performed, injecting blood of F13 positive outbreds into inbred B13/13 eggs. No GVH stimulation attributable to MHC determinants was found. In MLR, responder cells from outbred MHC heterozygous chickens, which typed F13/x, were stimulated by inbred F13/13 homozygous typing cells, and weak, but significant, reactions were found. Further analysis in the accompanying paper, however, revealed no difference in the lymphocyte activating determinants (Lads) of inbred and outbred birds typing F13 and L13. No individual has yet been found which carries one of these antigens in the absence of the other.

Animals↗
PubMed1982

The major histocompatibility complex of outbred chickens. II. Analysis of the typing response in mixed lymphocyte culture stimulated by homozygous typing cells.

MLR phenotypes of outbred and inbred chickens typing B13 of the major histocompatibility complex (MHC) of the chicken were compared. F1 hybrids of outbred and inbred B13 positive chickens were analysed in mixed lymphocyte culture (MLC). The intermediate strength responses of cells from B13 heterozygous outbred chickens stimulated by inbred B13 homozygous chicken cells were not due to minor variations of B encoded lymphocyte activating determinants (Lads). Nor were Lads encoded by genes unlinked to the B complex responsible for these reactions. In contrast, F1 anti-parental type reactions were observed, and these alone are probably responsible for the intermediate strength reactions so often seen in typing of heterozygous outbreds with homozygous typing cells.

Animals↗
PubMed1982

Major histocompatibility genes in egg-laying hens.

A common base population of White Leghorn was "synthesized" for a joint project on the genetics of egg-laying, undertaken by animal breeding geneticists in 4 Scandinavian countries. After 6 to 7 generations of line selection for various egg-laying parameters, MHC typing was undertaken of both the selection lines in Denmark, Norway, and Sweden and the respective control lines representing the common base population. Ten MHC haplotypes were defined which jointly accounted for about 95% of the MHC gene pool of the base population. The 2 haplotypes which were predominant in the base population, B15 and B19, responded very differently to the selection pressures applied.

Animals↗
PubMed1980

Linkage disequilibrium of MHC genes in the chicken. I. The B-F and B-G loci.

Two loci of the chicken MHC (the B complex) are expressed in erythrocytes, B-F and B-G. The former is homologous to the murine K and D loci and is also expressed in all white blood cells, while the latter is apparently restricted to RBC and is of unknown relationship to H-2 and HLA loci. A recombinant between two congenic, MHC-different strains, CB and CC, has permitted the production of antisera specific for the B-F and B-G alleles of these two strains, and these and other antisera have been used for typing of outbred populations of various chicken breeds. The cross-reactions found with haplotypes other than the donors' are extensive, sometimes even extreme, but it is possible to narrow the specificity of the typing sera by appropriate absorptions. With absorbed sera we have found a linkage disequilibrium which is almost certainly even stronger than that reported in studies of mammalian MHC loci. We hve also made observations which suggest that the gametic association of a given set of B-F and B-G alleles is probably not merely a matter of random crossing-over events.

Absorption↗
PubMed1979

Elution of chicken Ig from fixed target cells.

A method is described for preparing fixed chicken peripheral blood cells (PBC) for absorption of allo-antibodies and their subsequent elution. Glutaraldehyde fixation was satisfactory, and with 8 M urea elution haemagglutinating activity was preserved.

Adsorption↗