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I S Trowbridge

Publications and source records attributed to I S Trowbridge.

117 records · Page 7Linked to original sources
PubMed1973

Mitogenic properties of lectin and its chemical dervatives.

A mitogenic lectin that has a carbohydrate-binding specificity similar to that of concanavalin A (Con A) can be isolated from pea seeds. Chemical modification (succinylation, acetylation, or treatment with the diazonium salt of sulfanilic acid), changes its biological properties. In mitogenic stimulation of mouse spleen cells and in hemagglutination, the differences between the chemically modified pea lectin and the native molecule are similar to those observed between succinyl-Con A and native Con A. However, whereas chemical modification converts tetrameric Con A to a dimeric molecule, similar treatments of the pea lectin do not change its quaternary structure. The results of binding studies of the pea lectin and its derivatives to mouse spleen cells suggest that the differences in biological activities may be explained by a reduction in binding affinity of the pea lectin for glycoproteins on the spleen cell surface after chemical modification.

Acetates↗
PubMedDate not supplied

Structural requirements for high efficiency endocytosis of the human transferrin receptor.

Wild-type and mutant human transferrin receptors (TR) have been expressed in chicken embryo fibroblasts using a helper-independent retroviral vector. By functional studies of the mutant TRs, we have identified the tetrapeptide sequence, YXRF, in the cytoplasmic tail of the receptor as the internalization signal required for high efficiency endocytosis and shown that transplanted internalization signals from the low density lipoprotein receptor (LDLR) and the cation-independent mannose-6-phosphate receptor (Man-6-PR) are able to promote rapid internalization of the human TR. A six-residue LDLR signal, FDNPVY, is required for activity in TR, whereas a four-residue Man-6-PR signal, YSKV, is sufficient. These data indicate that internalization signals are interchangeable self-determined structural motifs and that signals from type I membrane proteins are active in a type II receptor. Putative internalization signals in the cytoplasmic tails of other receptors and membrane proteins can be identified based on the sequence patterns of the LDLR, Man-6-PR, and TR signals. Two such putative four-residue internalization signals, one from the poly-Ig receptor and one from the asialoglycoprotein receptor, were tested for activity by transplantation into TR and were found to promote high efficiency internalization. These results suggest that an exposed tight turn is the conformational motif for high efficiency endocytosis.

Amino Acid Sequence↗
PubMedDate not supplied

Detection of a novel human class II HLA antigen.

Genetic, molecular and cellular analyses of the HLA-D region of the major histocompatability complex (MHC) in man have led to the definition of three different products. Two of these, DR and MB (the latter also known as DC (ref. 1) and LB-E (ref. 2)) are defined with serological reagents; the third, known as SB (ref. 3) and PL-3 (ref. 4) is defined with primed lymphocyte typing (PLT) cells. The classical features attributed to HLA-D region encoded (class II) molecules are that they are cell-surface dimers consisting of a structurally conserved alpha-chain noncovalently associated with a polymorphic beta-chain and that they are found primarily on B lymphocytes, some monocyte populations, endothelial and certain other cells. Using these criteria a monoclonal antibody, B7/21, was described as reactive with HLA-DR (ref. 7). We have now re-evaluated B7/21 antibody reactivity using mutant lymphoblastoid cell lines. It appears that this antibody does not react with the molecularly defined D region products described to date but instead, recognizes a class II antigen with distinctive molecular characteristics. We provisionally refer to this antigen as FA.

Antibodies, Monoclonal↗
PubMedDate not supplied

Immunoglobulin-like nature of the alpha-chain of a human T-cell antigen/MHC receptor.

Although the receptor with which T cells bind specific antigen can, like immunoglobulin, distinguish between antigens which differ only slightly in structure, it is unique in recognizing antigen only in conjunction with one of the self proteins of the major histocompatibility complex (MHC restriction). The receptor was identified and characterized in mouse and man by using monoclonal antibodies to receptor idiotypes, and consists of two disulphide-linked polypeptides, and acidic alpha-chain and a neutral to slightly basic beta-chain. Peptide maps have shown that, like immunoglobulin, both chains vary for receptors of different specificities. T-cell-derived cDNA clones have recently been identified in mouse and man encoding immunoglobulin-like molecules. These were identified as derived from beta-chain genes through a partial N-terminal protein sequence of the beta-chain isolated from a human T-cell tumour. We have now purified the alpha- and beta-chains of the receptor of the human T-cell leukaemia line HPB-MLT, and have determined the amino acid sequence of several tryptic peptides derived from each chain. Our results further confirm that the previously reported cDNA clones encode beta-chains. The sequence of the alpha-chain peptides identify this as another immunoglobulin-like polypeptide chain. Particularly striking was an alpha-chain peptide with high homology to the conserved portion of the immunoglobulin J segment and T-cell receptor beta-chains. Surprisingly, the alpha-chain peptides show little similarity to the sequence predicted by two overlapping putative murine alpha-chain cDNA clones.

Amino Acid Sequence↗
PubMedDate not supplied

Thymocyte subpopulation enriched for progenitors with an unrearranged T-cell receptor beta-chain gene.

The development of T cells within the thymus is not well understood. It is known that thymocytes are derived from a progenitor cell in the bone marrow, the prothymocyte, and that cells in the subcapsular area of the thymus can give rise to progeny in both the cortex and the medulla. However, it is not clear whether all medullary thymocytes are necessarily derived from cortical cells. In particular, it has been difficult to distinguish intrathymic progenitor cells. Recently, however, Lesley et al. have defined a thymocyte subpopulation which can be isolated by treatment of the thymus with cytotoxic anti-Thy-1 antibodies and that seems to be enriched for thymocyte progenitors as measured first by its ability to repopulate transiently the thymus of an irradiated host, and second, by its high content of cells bearing Pgp-1 (refs 10, 11), a cell-surface glycoprotein of relative molecular mass 95,000 that is present on most or all prothymocytes of the bone marrow and on fetal thymocytes, but on only a few per cent of cells in the adult thymus. We show here that the gene encoding the beta-chain of the T-cell receptor for antigen, which is rearranged during T-cell ontogeny, is predominantly in the germline configuration in these cells.

Animals↗