Biomedical subjects

J Ohgama

Publications and source records attributed to J Ohgama.

5 recordsLinked to original sources

PubMed1996

A new solid-phase assay system using magnetic force on blood group serology.

A new solid-phase assay system has been developed for the detection of irregular antibodies in plasma and serum specimens. By means of a magnetic indicator cell, we have established a sensitive and easy-to-handle antihuman globulin (AHG) test involving magnetic-mixed passive hemagglutination (M-MPHA). Comparative studies of M-MPHA with conventional AHG tests demonstrated that this is sufficiently sensitive and specific to detect irregular antibodies to red blood cells. Elimination of centrifugation in this test seems to open the way toward new standardization of solid-phase systems.

Biological Assay↗

PubMed1994

Functional studies on MEL-14+ and MEL-14- T cells in peripheral lymphoid tissues.

Functions of MEL-14+ T cells and MEL-14- T cells in peripheral lymphoid tissues were analyzed and compared. The MEL-14- T cells, representing a minor subpopulation of spleen and lymph node T cells, generated considerably higher mixed lymphocyte reaction and mitogen responses than the MEL-14+ T cells in any lymphoid tissues studied. Furthermore, upon stimulation with ConA the MEL-14- CD8+ T cells produced significantly larger amounts of IL-2 and IFN-gamma than MEL-14+ CD8+ T cells did. A similar but less marked observation was obtained with the CD4+ T cell population. Furthermore, when B10.BR mice were immunized with AKR (Mls-1a) spleen cells, the proportion of the Mls-1a reactive V beta 6+ T cells from draining lymph nodes increased and a substantial proportion of the increasing V beta 6+ T cells was shown to be MEL-14-. The present findings on the whole indicate that MEL-14- T cells in the peripheral lymphoid tissues are at functionally high levels and may represent memory cells which have been previously stimulated in vivo.

Animals↗

PubMed1993

[Distribution and function of gp90MEL-14 positive and negative T lymphocytes].

The expression of gp90MEL-14 molecules on lymphocytes in vitro was extremely unstable. Even in the course of usual procedures for preparing single cell suspension, the amount of gp90MEL-14 was down-or up-regulated depending on the condition. Addition of NaN3 in the medium for preparing cell suspension stabilized the level of gp90MEL-14 and enabled to quantify the precise amount of gp90MEL-14 on various lymphoid cells, which appeared to reflect the expression pattern of gp90MEL-14 in vivo. By using this simple method, it was clearly demonstrated that the proportion of gp90MEL-14 positive cells and amount of gp90MEL-14 on the cells were associated with the anatomical and functional distance from endothelial cells of high endothelial venule in peripheral lymph nodes. Furthermore, the expression of gp90MEL-14 showed the reverse association with that of Pgp-1. When immunological functions were compared between gp90MEL-14 positive T cells and gp90MEL-14 negative T cells, the latter gp90MEL-14 negative T cells generated higher responses than gp90MEL-14 positive cells in mixed lymphocyte reaction. Furthermore, upon stimulation with concanavalin A (Con A), phytohaemaggultinin or immobilized anti-CD3 antibodies, gp90MEL-14 negative CD8+T cells showed significantly higher proliferative responses and generated extremely higher amounts of IL-2 and IFN-gamma than gp90MEL-14 positive CD8+ T cells did. By contrast, among the CD4+ T cell subpopulations no difference in the Con A response was observed and only slightly higher IL-2 secretion was detected in gp90MEL-14 negative CD4+ T cells than in gp90MEL-14 positive cells. The present findings demonstrate that gp90MEL-14 negative CD8+ and in some case CD4+ T cells, which make up a minor T cell subpopulation in peripheral lymphoid tissues are in functionally active state in vivo and may play a different role from major gp90MEL-14 positive T cells.

Animals↗

PubMed1992

Quantitative analysis of MEL-14 expression on various lymphocyte subpopulations.

Amounts of gp90MEL-14 molecules in various lymphocyte subpopulations were analyzed. The expression of gp90MEL-14 was rapidly up-regulated in the course of usual procedures for preparing single cell suspensions. On the other hand, the gp90MEL-14 expression was down-modulated after short term culture in the presence of PMA. Addition of NaN3 in the medium for preparing cell suspension was shown to stabilize the expression profile of the gp90MEL-14. By this simple improvement, we could successfully evaluate the precise amounts of gp90MEL-14 expressed on various lymphoid cells which appeared to reflect the expression pattern of gp90MEL-14 in vivo. The proportion of MEL-14+ cells and amounts of gp90MEL-14 on the cells were clearly associated with the anatomical and functional distance from endothelial cells of HEV in peripheral lymph nodes. The present findings, thus, support the role of gp90MEL-14 molecules as homing receptors for HEV that was originally proposed by Weissman and his colleagues.

Animals↗

PubMed1991

Distribution of MEL-14+ cells in various lymphoid tissues.

The distribution of MEL-14+ lymphocytes was investigated by both fluorocytometric analysis and complement-dependent-cellular-cytotoxicity (CDCC) tests in which rabbit anti-rat Ig was added with complement at a secondary step. When CDCC was employed to detect MEL-14+ cells, almost half of the thymocytes were found to be MEL-14+ in various strains of mice. This high proportion of MEL-14+ cells stands in striking contrast to prior reports. Furthermore, when determined by fluorocytometric analysis, MEL-14+ cells were found to comprise more than 80% of the cells in the thymus. The MEL-14+ thymocytes comprised both immature subsets (CD4-8-, CD4+8+) and mature subsets (CD+8-, CD4-8+). MEL-14 brightly positive (MEL-14high) cells, however, were located mainly in mature T cell subpopulations within the thymus. The MEL-14high thymocytes appeared to be susceptible to the CDCC method. Most of MEL-14+ cells present in spleens and lymph nodes were shown to be included in the MEL-14high population. The MEL-14+ cells susceptible to treatment with MEL-14, rabbit anti-rat Ig plus complement in the spleen and lymph node were restricted to cells of the T-lineage. These data suggest that T cells may change from cells with low expression of the MEL-14 antigens at their surface to cells with high MEL-14 antigens in the process of differentiation. Furthermore, these findings indicate that MEL-14 molecules may be used as a surface marker to characterize an important T cell subpopulation.

Animals↗