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S L Morrison

Publications and source records attributed to S L Morrison.

At least 127 records · Page 7Linked to original sources
PubMed1989

Developmental regulation of membrane and secretory Ig gamma 2b mRNA.

To better understand the developmental regulation of membrane and secretory forms of Ig Heavy chain mRNA, mutations were made in a gamma 2b gene in vitro and assayed for their expression in cell lines representative of early and late stages of B cell development. Processing of the gamma 2b mRNA did not change with the amount of message produced, demonstrating that the production of predominantly secretory mRNA in plasma cells is not the consequence of increased message synthesis. The length of the intron between the secretory and membrane exons was found to affect the relative expression of secretory and membrane mRNA, but this effect was also observed in non-lymphoid cells, suggesting that the intron "gradient effect" does not identify the processing reaction which is regulated during B cell differentiation. Deletion of the signals for the splice from CH3 to the membrane exons resulted in the exclusive production of secretory mRNA irrespective of the developmental stage of the recipient cell, suggesting that this splice reaction plays a role in regulating these mRNA, and that competition between the two polyadenylation sites does not dictate the relative expression of the two forms of message. Appropriate ratios of the two forms were produced from a 2.3-kbp fragment of the gamma 2b gene containing the secretory cleavage and membrane splice signals in the context of a different transcription unit. These results suggest that the changes in the relative expression of secretory and membrane gamma 2b mRNA during B cell development are mediated by a competition between cleavage at the secretory polyadenylation and splicing from CH3 to the membrane exons.

Animals↗
PubMed1989

The effect of isotype and the J kappa region on antigen binding and idiotype expression by antibodies binding alpha (1----6) dextran.

Gene transfection and expression techniques have been used to produce three antibodies specific for alpha (1----6) linked dextran B512 with altered isotypes and J kappa regions. Expression of the L chain V region joined to J kappa 4 or J kappa 5 instead of to J kappa 2 reduced or abolished dextran binding. One antidextran with a reduced binding constant for dextran had the same combining site size as the parental mAb. Transfectoma Ig unreactive with dextran B512 did not bind to other class I or class II dextrans. Antibodies with J kappa 4-containing L chains expressed the 10.16.1 (anti-alpha(1----6) dextran) idiotype. In contrast variants expressing L chains with J kappa 5 lost idiotype expression, except when oligosaccharide is present on VH; all antibodies with J kappa 5 L chains continued to bind dextran but with reduced affinity. The presence of carbohydrate in VH may alter the conformation of both paratope and idiotope. Alteration of H chain isotype did not appear to significantly alter the ability of the antidextran to bind Ag; an exception may be that switching V regions to the IgM C region may decrease the apparent affinity for Ag.

Animals↗
PubMed1989

Amino acid substitutions in VH CDR2 change the idiotype but not the antigen-binding of monoclonal antibodies to alpha(1----6)dextrans.

An idiotype defined by mAb and polyclonal antibodies to 10.16.1, an anti-alpha(1----6) dextran was previously reported to be expressed on most BALB/c anti-alpha(1----6)dextrans with groove-type sites and to involved CDR3 and probably CDR2. By comparing amino acid sequences of VH and VL derived from cDNA of idiotype+ and idiotype- anti-alpha(1----6)dextran hybridoma proteins, an idiotope was assigned to VH CDR2. Substitution of phenylalanine for leucine at residue 52 in CDR2 coupled with amino acid changes at either residue 58 or residues 57 and 60 abolished expression of this idiotype without affecting Ag binding.

Amino Acid Sequence↗
PubMed1989

Regulation of the production of secretory and membrane immunoglobulin during lymphocyte development.

An area of great controversy in molecular immunology is the mechanism by which the differential expression of secretory and membrane immunoglobulin heavy chain is regulated during B cell development. Since the changes in expression of the two proteins are determined largely by the steady state levels of the mRNAs that encode them, recent work has focused on the regulation of the expression of the two messages. This problem is central to understanding humoral immunity, with the specific antigen driven switch from antibody as receptor to antibody as secreted product and may be of direct relevance to some forms of the common variable immunodeficiency syndrome. In addition, numerous other genes have been shown to be regulated by alternative RNA processing. Since its beginnings, research in immunology has brought about profound changes in our view of biology. Jenner's landmark experiment, inducing a minor illness to prevent a major one, showed that the body's future susceptibility to a particular disease could be manipulated. More recently the demonstration that immunoglobulin V, D, and J gene segments, originally spread over many kilobases (kbs) in the genome, must be assembled to form a functional heavy chain gene has shattered both the concept of a genome fixed at fertilization and the "one gene, one protein" rule. The alternative processing of heavy chain transcripts to produce secretory and membrane forms of immunoglobulin has demonstrated how the same gene can give rise to proteins with alternative structures. Since the discovery of the role of alternative RNA processing in heavy chain mRNA synthesis, numerous other cellular genes have been shown to be regulated by modulation of RNA processing pathways.

Animals↗
PubMed1989

Psychological, topographic EEG, and CT scan correlates of frontal lobe function in schizophrenia.

This study examined frontal lobe function in a group of 20 patients with schizophrenia, on and off medication, compared to 20 normals matched for age, sex, handedness, intelligence, and educational level. Schizophrenic patients generally did not perform as well as normals on the Wisconsin Card Sorting Test (WCST). Patients off medication performed less well on this test than those on medication. Those on medication did not perform as well as those off medication on the design and word fluency tests, which suggested that medications may affect various aspects of frontal lobe function differently. During the WCST, normal subjects demonstrated an increase in beta mean frequency of the electroencephalogram in frontal and centrotemporal regions which was not statistically significant in either schizophrenic group. This shift in beta mean frequency was found to correlate positively with performance on the WCST in normals, but not in patients. Patients with more negative symptoms tended to show a smaller increase in beta mean frequency during the WCST. Performance on the WCST was correlated negatively with ventricle-brain ratio in all subjects, suggesting that frontal lobe function might be related to computed tomographic measures in the normal population as well as in schizophrenic patients. There was no correlation with performance on the WCST and length of illness.

Adult↗
PubMed1989

Psychometrics of the Schalling-Sifneos and Toronto Alexithymia Scales.

Two measures of alexithymia, the Schalling-Sifneos (SSPS) and the Toronto Scales (TAS) were administered to 178 male and female undergraduate students. For both measures alexithymia appears to decrease with age. Five factors for the TAS were retained accounting for 35% of the variance and for the SSPS a three-factor solution was determined accounting for 53% of the variance. The robustness of the solution analyzed with the TAS reflected greater stability. The factor structure of the TAS seemed more consistent with the concept of alexithymia than that of the SSPS.

Adolescent↗
PubMed1988

Glycosylation of a VH residue of a monoclonal antibody against alpha (1----6) dextran increases its affinity for antigen.

We have observed that antidextran hybridomas with potential N-linked glycosylation sites in VH have higher affinity for polymeric dextran and for isomaltoheptaose than those lacking potential glycosylation sites. In these studies we have used gene transfection and expression techniques to verify that the carbohydrate addition sites in VH were used. The carbohydrate of the VH region was accessible for binding by the lectin Con A. By ELISA analysis it was demonstrated that the aKa of the antibody for dextran was influenced by the presence of carbohydrate in VH, with the aglycosylated antibody having an aKa 15-fold lower than its untreated counterpart. The aKa for antigen of antibodies that contain carbohydrate only in their constant region was unaffected by lack of carbohydrate. Thus, not only the amino acid sequence of the variable region but also its carbohydrate moieties can determine the magnitude of the antigen-antibody interaction.

Amino Acid Sequence↗
PubMed1988

Segmental flexibility and complement fixation of genetically engineered chimeric human, rabbit and mouse antibodies.

We generated a family of chimeric immunoglobulin G (IgG) molecules having identical antigen-combining sites for the dansyl (DNS) hapten, in conjunction with nine heavy chain constant (CH) regions. This family of antibody molecules allows comparison of CH dependent properties independent of possible variable region contributions to IgG function. The segmental flexibility and complement fixation activity were measured of six genetically engineered molecules (the four human IgG isotypes, mouse IgG3 and rabbit IgG) and the remaining three mouse IgG isotypes, (IgG1, IgG2a and IgG2b), isolated previously by somatic cell genetic techniques. These properties of antibody molecules each correlate with the length of the immunoglobulin hinge region which separate the first and second CH (CH1 and CH2) domains. These results attribute a structural basis for two critical properties of antibody molecules.

Amino Acid Sequence↗
PubMed1988

An immunoglobulin heavy chain gene deletion at direct repeats: nucleotide sequence and effect on mRNA accumulation.

The DNA from the mouse myeloma cell, I17, which produces aberrant gamma 2b heavy chain mRNAs, was cloned and sequenced. The I17 mutant, and its parent line 10.1, share a small deletion at the splice junction of the CH1 domain which results in the absence of CH1 sequences from the mRNA. In addition, the genomic DNA of I17 has a deletion of 253 nucleotides which fuses the CH2 and CH3 exons, causes a frameshift of the next 43 amino acids and results in a truncated protein. The deleted nucleotides are flanked by two direct repeats of the CAGCA pentamer in the normal gene. One copy of the repeat and the interposed DNA is removed in the mutant. The DNA deletion is colinear with the mRNA. Both I17 and 10.1 cells have decreased accumulation of the secretory-specific gamma 2b mRNA. The amounts of membrane-specific gamma 2b mRNA are also affected in the mutants.

Animals↗
PubMed1988

The IgA myeloma W3129 contains a deletion in CH3 which prevents the formation of the membrane form of heavy chain mRNA.

We report here a 54 base pair deletion in the CH3 exon of the alpha gene in the mouse myeloma W3129. This deletion results in a loss of 18 amino acids and a change from a glycine to a serine at position 464. The extent of the deletion was determined by sequencing a portion of CH3 cloned from a variant of W3129, and S1 nuclease protection showed the deletion pre-exists in the parental cell line. The deletion removes the donor splice site normally used in joining CH3 to the alpha membrane (MB) exon when forming MB-specific mRNA. Examination of cytoplasmic RNA by blot hybridization and S1 nuclease protection using MB-specific probes showed a complete lack of membrane mRNA in W3129 and its derivatives. An RNA transcript of unknown origin and function which includes sequences from the CH3-MB intron was seen in W3129 and in J558, an IgA, lambda myeloma with specificity for alpha (1----3) linked dextrans. We discuss the possible influence of the mutation on the W3129 protein. In contrast to the other myelomas studied in this laboratory, light chain loss variants are readily isolated from W3129 and are stable in their production of heavy chain [Dackowski and Morrison (1981) Proc. natn. Acad. Sci. U.S.A. 78, 7091-7095].

Amino Acid Sequence↗
PubMed1988

Production and characterization of genetically engineered antibody molecules.

Expression of antibody heavy- and light-chain genes by transfection permits the production of monoclonal antibodies with improved biological and antigen-binding properties. The immunoglobulin genes are placed in vectors containing a gene for encoding a protein that provides a biochemically selectable function in eukaryotic cells; these vectors are transfected into myeloma and hybridoma cells. Selection of drug-resistant cells permits the efficient isolation of the rare cells that express the transfected DNA. By placing heavy and light chains on plasmids with different selectable markers, one can deliver heavy- and light-chain genes simultaneously to the same cell. The transfected immunoglobulin genes are efficiently expressed and the proteins produced are a faithful mirror of the genes that were introduced. Using the standard techniques of genetic engineering and gene transfection, we can now produce antibodies of widely varying structures, including chimeric antibodies with segments derived from different species. These antibodies provide useful reagents to study structure-function relationships within the antibody molecule. Ultimately it will be possible to produce a new generation of antibody molecules with improved antigen-binding properties and effector functions.

Animals↗
PubMed1987

Different VL and VH germ-line genes are used to produce similar combining sites with specificity for alpha(1----6)dextrans.

Monoclonal antibodies to alpha(1----6)dextrans produced in mice immunized with the T-independent antigens alpha(1----6)dextran or the stearylisomaltosyl oligosaccharides have been characterized immunochemically. To correlate the immunochemical properties of these monoclonal antibodies with their primary structure, we have sequenced the variable (V) regions of the light (L) and heavy (H) chains. Three V kappa germ-line genes belonging to two major gene families were used; differential J usages also contribute to diversity. Five different VH germ-line genes belonging to three major VH families were used. The VH genes were further modified by junctional diversity and differential J usage and possibly by somatic mutations. The effects of these modifications on the fine specificities of anti-alpha(1----6)dextrans are discussed. Thus far, six different combinations of VLJL-VH(D)JH chains that form groove-type combining sites specific for alpha(1----6)dextran have been found. We conclude that entirely different VL and VH can form combining sites specific for the internal linear sequence of alpha(1----6)dextran.

Amino Acid Sequence↗
PubMed1987

Chimeric antibody with human constant regions and mouse variable regions directed against carcinoma-associated antigen 17-1A.

We have cloned the genomic DNA fragments encoding the heavy and light chain variable regions of monoclonal antibody 17-1A, and we have inserted them into mammalian expression vectors containing genomic DNA segments encoding human gamma 3 and kappa constant regions. The transfer of these expression vectors containing mouse-human chimeric immunoglobulin genes into Sp2/0 mouse myeloma cells resulted in the production of functional IgG that retained the specific binding to the surface antigen 17-1A expressed on colorectal carcinoma cells.

Amino Acid Sequence↗
PubMed1987

Genetically engineered antibody molecules and their application.

Immunoglobulin genes can be efficiently expressed following transfection into myeloma cells. Using protoplast fusion, transfection frequencies greater than 10(-3) can be achieved. Compatible plasmids containing two different selectible markers are used to simultaneously deliver heavy and light chain genes to the same cell. To produce molecules with differing specificities the rearranged and expressed variable regions can be cloned from the appropriate hybridoma. In some cases, variable regions from cDNAs can be inserted into the expression vectors. It is possible to manipulate the immunoglobulin genes and produce novel antibody molecules. Antibodies have been produced in which the variable regions from mouse antibodies have been joined to human constant regions. In addition, antibodies with altered constant regions have been produced. These genetically engineered antibodies provide a unique set of reagents to study structure-function relationships within the molecule. They also can potentially be used in the diagnosis and therapy of human disease.

Animals↗