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Biomedical subjects

A F Williams

Publications and source records attributed to A F Williams.

At least 289 records · Page 16Linked to original sources
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A glycophospholipid covalently attached to the C-terminus of the Thy-1 glycoprotein.

The Thy-1 glycoprotein is a very abundant cell surface molecule of rat thymocytes and neuronal cells with the properties of a molecule that inserts into the lipid bilayer. The hydrophobicity is due to a glycophospholipid component covalently attached to the carboxy group of the C-terminal cysteine residue. The mature glycoprotein does not contain a stretch of hydrophobic amino acids that could traverse the membrane bilayer. These findings present a new mode of membrane attachment for a cell surface molecule that can mediate lymphokine release and cell division after cross-linking by antibodies.

Amino Acid Sequence↗
PubMedDate not supplied

Inhibition of mixed lymphocyte response by monoclonal antibody specific for a rat T lymphocyte subset.

Cell-surface differentiation antigens which are associated with particular lymphocyte subsets are likely to be molecules which mediate specific functions of the cells which display them. One way to investigate this hypothesis is to see whether antibodies directed against such antigens will inhibit functional systems. This approach can be attempted with confidence if monoclonal antibodies are used, as these react with one antigenic determinant only and can be used in purified form. In this report we show that a monoclonal antibody which is specific for a subset of rat tT lymphocytes inhibits the mixed lymphocyte response (MLR). The antibody acts on the responder cells without killing them.

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Detection of neuronal tissue from brain grafts with anti-Thy-1.1 antibody.

Grafting of neural tissue has been used to investigate the ability of central nervous system (CNS) axons to elongate into peripheral nerve grafts; to investigate the growth characteristics of material transplanted within the CNS; and to determine if grafts producing amines or peptides can replace a natural or experimentally induced depletion of these biogenic molecules. In such experiments donor tissue has been distinguished from host by injection into graft cells of horseradish peroxidase or radioactive leucine or by detecting biogenic molecules in the grafted tissue with antibodies. All these methods have limitations and a technique which allows identification of the total neuronal cell output from transplanted tissue would be a powerful tool in delineating host-graft interactions. Polymorphic cell-surface antigens have not previously been exploited as markers. The Thy-1 antigen is an abundant glycoprotein of neurones and in the mouse exists in two allotypic forms called Thy-1.1 and Thy-1.2. We now show that tissue from Thy-1.1-positive animals grafted into Thy-1.1-negative brains can be clearly identified in cryostat sections using an anti-Thy-1.1 monoclonal antibody conjugated with peroxidase. We have used the method to study grafts from normal fetal mice which correct a developmental deficiency when transplanted into hpg mutant mice.

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Transferrin receptor on endothelium of brain capillaries.

The blood/brain barrier prevents the passive diffusion of proteins and metabolites from cerebral blood vessels into tissue spaces around neuronal and glial cells. To provide nutrients for these cells, transport mechanisms must exist and indeed have been demonstrated for metabolites. We now show that monoclonal antibodies against rat and human transferrin receptors label blood capillaries in the brain but not in other tissues. In the rat this labelling occurs after injection of antibody into the blood, thus the receptors seem to be accessible at the endothelial surface. It is possible that transferrin receptors are expressed on these cells to allow transport of transferrin (and thus iron) into brain tissues.

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PubMedDate not supplied

Striking similarities between antigen receptor J pieces and sequence in the second chain of the murine CD8 antigen.

The CD8 antigen is a marker for T-lymphocyte subsets that is absent from helper T cells but expressed on cytotoxic T cells which recognize foreign determinants in association with class I major histocompatibility complex (MHC) antigens. It has been suggested that CD8 plays some part in recognition by CD8+ cytotoxic T cells since anti-CD8 antibodies can block their functions and the human CD8 antigen contains a domain with clear similarities to immunoglobulin and T-cell receptor (TCR) variable-region (V) domains. Human CD8 antigen is thought to be a homodimer but in the mouse and rat the equivalent antigens (alternatively called Lyt2,3 and OX8) are heterodimeric. Rat CD8 contains two chains of relative molecular mass 32,000 (32K) and 37K: the 32K chain is the rat homologue of human CD8 and mouse Lyt2. We describe here the molecular cloning of the rat 37K chain using an oligonucleotide probe predicted from peptide sequence. The full protein sequence is derived from the complementary DNA and matches limited peptide sequence for mouse Lyt3. The new sequence is more like immunoglobulin and T-cell receptor V domains than other T-cell antigens and includes a patch that is almost identical to some joining (J) piece sequences. This suggests that the CD8 and receptor heterodimers may have evolved directly from a common ancestor.

Amino Acid Sequence↗