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Biomedical subjects

K Stefansson

Publications and source records attributed to K Stefansson.

At least 73 records · Page 4Linked to original sources
PubMed1988

Developmental changes in the molecular weights of polypeptides in the human CNS that carry the HNK-1 epitope and bind Phaseolus vulgaris lectins.

The binding patterns of electrophoresed polypeptides from homogenates of human frontal lobe, cerebellum, and spinal cord obtained at various stages of development were determined for several lectins with specificities for a wide range of oligosaccharides. A discrete developmental change in the molecular-weight pattern was seen only among polypeptides binding the two Phaseolus vulgaris agglutinins, E-phytohemagglutinin (E-PHA) and L-PHA. With increasing maturity, the apparent molecular weights of the major polypeptides binding these two lectins progressively decreased. Furthermore, at all stages of development, E-PHA and L-PHA bound to the same polypeptides as the monoclonal antibody HNK-1, which recognizes a carbohydrate epitope on polypeptides that may play roles in cell adhesion. Based on the carbohydrate specificities of the two PHAs, we conclude that it is likely that the HNK-1 epitope resides on a triantennary N-linked oligosaccharide bisected by N-acetylglucosamine.

Adult↗
PubMed1988

A peanut agglutinin binding glycoprotein in CNS myelin and oligodendrocytes.

We isolated and characterized a 120-kd PNA-binding polypeptide from the human CNS. This polypeptide is linked to membranes through a PI linkage. After release from membranes by PLC it measures 105 kd, 30 kd of which appear to be contributed by N-linked carbohydrates. We isolated the polypeptide by the use of PLC and PNA affinity chromatography and used it to raise polyclonal antibodies and to determine the N-terminal sequence. Immunohistochemical and immunochemical studies using these antibodies showed that 120 kdpp is present in both myelin and oligodendrocytes.

Amino Acid Sequence↗
PubMed1987

Rejection of fetal neocortical neural transplants by H-2 incompatible mice.

In order to examine questions concerning immunologic privilege of the central nervous system, we placed neocortical transplants into cerebral ventricles of mice. We compared the fates of transplants between fully H-2 compatible (isografts) and H-2 incompatible (allografts) animals. Histologic evaluation comparing animals from iso- and allograft groups revealed significant differences in the number of inflammatory cells and in the degree of necrosis within the grafts. Response to allografted tissue within the brain mimics that seen in several immune-mediated diseases of the nervous system in that neurons appear to be selectively spared. Only upon subsequent stimulation of the host's immune system with an orthotopic skin graft bearing the major histocompatibility complex antigens of the neural graft are neurons destroyed. Immunohistochemical evaluation revealed that the inflammatory cell infiltrates in and around the allografts were composed of Lyt-2+, L3T4+, and Mac-1+ cells. In addition, Ia+ endothelial cells as well as Ia+ parenchymal CNS cells were found in both donor and host tissue of allografted animals. Hence, H-2 incompatible neural tissue transplanted to the CNS is recognized and rejected by the immune system of the recipient animal. The cellular infiltrates seen within the first weeks to months following transplantation of allogeneic CNS tissue resemble those seen in other allografts undergoing rejection. We conclude that the CNS is not unconditionally privileged as either a transplant site or as a source of transplanted tissue.

Animals↗
PubMed1987

An in vivo and in vitro analysis of systemic immune function in mice with histologic evidence of neural transplant rejection.

Histologic and immunocytochemical analyses of fetal neocortical tissue transplanted to the lateral ventricle of inbred adult mice indicate that this tissue survives transplantation well if the donor and host are isogeneic. The major histocompatibility complex (MHC) of the mouse is known as the H-2 locus. H-2-incompatible neural transplants (allografts), unlike their H-2-identical counterpart (isografts), are characterized by the presence of T cells comprising both major T-cell subsets and macrophages, and by a marked increase in the expression of both class I and class II (Ia) MHC antigens. These findings suggest a recognition of H-2 alloantigens by the host's immune system followed by an appropriate effector response. We report here our attempts to demonstrate systemic host sensitization to alloantigens in mice bearing H-2-incompatible intraventricular neural transplants. We measured the time to rejection of orthotopic skin grafts subsequent to neural transplantation, splenocyte proliferative responses to alloantigens in mixed lymphocyte cultures (MLC), and class I-restricted antigen-specific cytolytic T lymphocyte (CTL) activity. No significant differences were found in any of these tests of host systemic sensitization between mice with allogeneic neural transplants and those with isogeneic transplants or control animals. We conclude that intraventricular neural transplants, while recognized and affected by cells of the host's immune system, do not elicit a detectable systemic sensitization to class I H-2 alloantigens. Rejection of neural transplants may depend on sensitization to class II H-2 alloantigens, to so-called minor histocompatibility antigens, or some combination thereof.

Animals↗
PubMed1986

Exposure of binding sites for antibodies and concanavalin A on collagen by solubilization in hot urea. An immunoblot analysis.

The presence of urea during solubilization of collagenous samples for SDS PAGE had a marked effect upon mobility of collagenous polypeptides and upon binding of antibodies from certain rabbit antisera, antibodies from several human sera and binding of concanavalin A. When samples were solubilized with urea by heating at 100 degrees C the mobility of collagenous polypeptides was retarded relative to samples that had been heated without urea or exposed to urea without heating. Antibodies from the rabbit sera only bound on immunoblots to collagen that had been urea/heat-treated. Periodate oxidation and deglycosylation with trifluoromethanesulfonic acid abolished binding of the rabbit antibodies. The results indicate the presence of carbohydrate epitopes buried within collagenous polypeptides that are exposed by harsh denaturing conditions. Heating with urea appears to cause an unfolding of collagenous molecules beyond that produced by SDS solubilization without urea. These results underscore the necessity to pay close attention to conditions used to solubilize for electrophoresis samples that are subsequently used as targets for antibodies or other ligands.

Binding Sites↗
PubMed1986

Myelin-associated glycoprotein in the developing human retina.

The immunohistochemical presence of myelin-associated glycoprotein (MAG) in Müller cells of the developing human retina was examined with rat monoclonal antibodies to MAG and the peroxidase antiperoxidase (PAP) method of Sternberger. Retinas of various developmental stages ranging between 9-31 gestational weeks were stained. There was no staining in the retinas of 9-12-week embryos. Between 13-16 gestational weeks the staining was faint and located mostly in the inner and middle portion of the retina, primarily around the optic nerve head. After midterm, Müller cells invariably stained through all retinal layers. The staining increased gradually up to the twenty-third gestational week, when it reached the level found in the retinas of newborn children.

Antibodies, Monoclonal↗
PubMed1986

An epitope shared by central nervous system myelin and peripheral blood macrophages.

Lewis rats were immunized with a homogenate of human spinal cord. Splenocytes from the immunized rats were fused with cells from the SP2/0-Ag14 cell line to form hybrids that were subsequently screened immunohistochemically for secretion of antibodies against myelin. Thirty hybrids secreting anti-myelin antibodies were cloned. One secreted antibody (774) that immunohistochemically stained central nervous system (CNS) myelin but not peripheral nervous system (PNS) myelin also bound to the surface of peripheral blood macrophages. Hence we have identified an epitope that is shared by peripheral blood macrophages and CNS myelin.

Animals↗
PubMed1986

Two large glycosylated polypeptides found in myelinating oligodendrocytes but not in myelin.

Previous work has shown that high molecular weight polypeptides sharing epitopes with myelin-associated glycoprotein are transiently expressed in developing human central nervous system. We describe here the isolation of two of these polypeptides (150 and 225 kDa), their biochemical characterization, and their immunochemical localization. They are both glycosylated and 15 kDa of the apparent molecular mass of both polypeptides is contributed by N-linked carbohydrate moiety(ies). Both have multimeric forms held together by disulfide bonds. Immunochemical and immunohistochemical studies failed to show these polypeptides in myelin. However, in developing human central nervous system, one or both of them are present in the perikaryal cytoplasm and processes of cells with morphology consistent with actively myelinating oligodendrocytes.

Adult↗
PubMed1985

Circulating autoantibodies to the 200,000-dalton protein of neurofilaments in the serum of healthy individuals.

There is substantial evidence that human serum contains antibodies to many autoantigens. For example, all healthy people have autoantibodies (immunoglobulin M) to some undefined brain antigens. In this study immunoblots and immunohistochemical staining were used to detect antibodies to neural tissues in serum samples from 200 healthy people and 200 patients with various neurological diseases. Ninety-nine percent of the 400 subjects had serum immunoglobulin M and 95 percent had immunoglobulin G that bound to a 200-kilodalton protein in homogenates of neural tissues. In most cases there were no antibodies to anything else in the homogenates. The 200-kilodalton protein was the heaviest of the neurofilament triplet proteins. These observations do not support a role for antibodies to the 200-kilodalton protein of neurofilaments in the pathogenesis of neurological diseases.

Autoantibodies↗
PubMed1985

Pattern of reactivity of IgM from the sera of eight patients with IgM monoclonal gammopathy and neuropathy with components of neural tissues: evidence for interaction with more than one epitope.

It has been postulated that binding of monoclonal IgM from the sera of some patients with IgM monoclonal gammopathy and neuropathy to components of peripheral nerve may play a key role in the pathogenesis of the neuropathy. Serum IgM from these patients has been shown to bind to antigenic determinants shared by the myelin-associated glycoprotein (MAG) and a polar glycolipid from peripheral nerve. Here we describe a study of sera from eight patients with IgM monoclonal gammopathy and neuropathy. Five of the patients had serum IgM directed both against MAG and one or two polar glycolipids from peripheral nerve. One of the patients had serum IgM that bound to a peripheral nerve glycolipid but not to MAG; no one had serum IgM that bound to MAG but not to a peripheral nerve glycolipid. The relative affinity of IgM from the sera of the patients for proteins in peripheral nerves of chickens, dogs, and humans varied from patient to patient. These data indicate that the epitope against which the serum IgM from these patients is directed is not necessarily the same in all of the cases.

Animals↗
PubMed1985

Generation of monoclonal antibodies recognizing neuronal elements in formalin-fixed paraffin-embedded human tissue.

We used formalin-fixed human spinal cord and dorsal root ganglia as immunogens to generate monoclonal antibodies (mAb) which immunohistochemically react with neurons in formalin-fixed human tissue sections. Three of the mAb recognized all neuronal populations studied, including those in spinal cord, dorsal root ganglia, cerebellum, and cerebrum. A fourth mAb recognized neurons within spinal cord, dorsal root ganglia and dentate nucleus of cerebellum but not those in cerebrum or cerebellar hemispheres. This mAb, unlike the other three, did not recognize murine neurons. These data indicate the feasibility of generating mAb suitable for analysis of human pathological material in its most readily available form, formalin-fixed paraffin-embedded tissue.

Antibodies, Monoclonal↗