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H M Ladyman

Publications and source records attributed to H M Ladyman.

5 recordsLinked to original sources
PubMed1998

K21-antigen: a molecule shared by the microenvironments of the human thymus and germinal centers.

The mouse IgG1 monoclonal antibody (mAb) K21 recognizes a 230-kD molecule (K21-Ag) on Hassall's corpuscles in the human thymus. This mAb also stains cultured thymic epithelial cells as well as other epithelial cell lines, revealing a predominant intracellular localization. Further analysis with mAb K21 on other lymphoid tissues showed that it also stains cells within the germinal centers of human tonsils, both lymphoid (B) cells and some with the appearance of follicular dendritic cells. Double immunostaining of tonsil sections shows that K21-Ag is not expressed by T cells, whereas staining with anti-CD22 and -CD23 mAb revealed some double-positive cells. A subpopulation of the lymphoid cells express the K21-Ag much more strongly. This K21++/CD23++ subpopulation of cells is localized in the apical light zone of germinal centers, suggesting that K21-Ag may be an important marker for the selected centrocytes within germinal centers and may play a role in B-cell selection and/or development of B-cell memory. Flow cytometric analysis showed that K21-Ag is expressed on the surface of a very low percentage of thymocytes, tonsillar lymphocytes, and peripheral blood mononuclear cells. Analysis of purified/separated tonsillar T and B lymphocytes showed that T cells do not express the K21-Ag; in contrast, B cells express low levels of the K21-Ag, and this together with CD23 is upregulated after mitogenic stimulation. Our data therefore raise the possibility that the K21-Ag may play a role in B-lymphocyte activation/selection.

Animals↗
PubMed1996

Direct visualization of thymocyte apoptosis in neglect, acute and steady-state negative selection.

During thymocyte differentiation, the majority of the developing cells die in situ by apoptosis and are subsequently removed by macrophages. DNA fragmentation is one of the hallmarks of apoptosis and can be detected in situ by TdT-mediated dUTP-biotin nick end labeling (TUNEL). We used TUNEL combined with immunohistology to determine the sites of thymocyte apoptosis in mice transgenic for a TCR (F5) which recognizes a peptide (NP68) of the influenza virus nucleoprotein (NP) presented on the MHC class I H-2Db molecule. Apoptosis due to neglect was studied in F5 mice expressing a neutral MHC haplotype (F5/H-2q) and in beta 2-microglobulin-deficient F5 mice (F5/ beta 2m+). In both cases, the frequency of apoptotic cells was similar to that seen in F5/H-2b mice and non-transgenic C57BI/10 mice. Antigen-induced apoptosis was studied in F5 mice after i.p. Injection of the cognate NP68 peptide and in F5/NP double-transgenic mice. Three hours after peptide injection, apoptosis was high throughout the thymus cortex and clusters of apoptotic cells formed due to tissue macrophage uptake, whereas the thymic medulla remained unaffected. Massive recruitment of inflammatory cells into the thymus was seen as early as 1 h after peptide injection. Nine hours after peptide injection changes were apparent in the cortical epithelium and, by 4 days, the cortical network had collapsed to give scattered, compacted epithelial cells. In contrast, in F5/NP double-transgenic mice, thymocyte apoptosis induced by cognate self-peptide was localized at the cortico-medullary junction with little change seen in the epithelium of the cortex.

Animals↗
PubMed1992

A novel adhesion molecule in the murine thymic microenvironment: functional and biochemical analysis.

The rat monoclonal antibody (mAb) 4F1, raised against mouse thymic stromal cells, recognizes cortical epithelium in tissue sections of mouse thymus; however, in flow cytometry, activated leucocytes (T cells, B cells, and macrophages) and transformed thymocytes are also positive for the 4F1-antigen (4F1-Ag). Western blotting, under both reducing and nonreducing conditions, demonstrates that the molecule to which 4F1 binds is expressed in four forms, 29, 32, 40, and 43 kD, all of which carry N-linked carbohydrate; and that the structure is identical on epithelium and lymphocytes. The 4F1-Ag on cortical epithelium is partially sensitive to PI-PLC treatment, whereas on transformed epithelial and lymphoid cell lines, it was resistant to this enzyme. The molecule, therefore, may exist in both transmembrane and phosphoinositol-linked forms. In functional blocking experiments, mAb 4F1 gave inhibition of both T-cell proliferation in MLR and of cytotoxic T-cell killing of alloantigenic targets; it also blocked adhesion of transformed thymocytes to thymic epithelial cells in vitro. These molecular and functional characteristics suggest that the 4F1-Ag is a novel adhesion molecule that may be involved both in intrathymic T lymphocyte differentiation and in peripheral T-cell function.

Animals↗
PubMed1989

Elevated expression of the interleukin 4 receptor in carcinoma: a target for immunotherapy?

Studies using monoclonal antibody MR6, which is thought to bind to the interleukin-4 growth factor receptor (IL-4R), indicate that IL-4R molecules are upregulated in tumours of epithelial origin and that radiolabelled MR6 is effective as an in vivo tumour imaging agent. Immunohistochemical analysis of a wide range of solid tumours using monoclonal antibody MR6 has demonstrated elevated expression of the IL-4R on a variety of carcinomas. The equivalent normal tissue showed either weak or no expression of this molecule. No other tumours studied were positive. The molecular weight of the receptor on tumour cells was indistinguishable from that on normal tissue. These data raise the possibility that the IL-4R is the product of a novel oncogene such that elevated expression of this growth factor receptor could be involved in the process of carcinogenesis. Monoclonal antibodies to the IL-4R, such as MR6, may therefore be useful reagents not only for diagnosis and immunoscintigraphy, but also for in vivo antibody-guided therapy of epithelial cancers.

Blotting, Western↗