PubMed Health⌕ Search

Biomedical subjects

A Dimitriu

Publications and source records attributed to A Dimitriu.

At least 19 recordsLinked to original sources
PubMed1979

Activation of human B lymphocytes. XIV. Characterization of the precursor of the pokeweed mitogen-induced anti-sheep red blood cell plaque-forming cell.

The precursor of the pokeweed mitogen (PWM)-induced anti-sheep red blood cell (SRBC) plaque-forming cell (PFC) in human peripheral blood was characterized. By a variety of purification procedures, it was demonstrated to be a lymphocyte with surface characteristics of a B cell. Furthermore, it was demonstrated to bind to sheep erythrocytes (E) and thus segregated with the E-rosetting T cells when T cell enrichment was performed by differential fractionation of E-rosetting cells. This binding of the PFC precursor to E was blocked by pretreating the lymphocyte with anti-human Ig before E rosetting, indicating that the PFC precursor specifically bound to SRBC by a surface Ig molecule with binding specificity for sheep red blood cell determinants. Hence, the precursor of the PWM-triggered anti-SRBC PFC is a B lymphocyte with surface Ig expressing specificity for SRBC.

Animals↗
PubMed1978

Mitogenic analysis of murine B-cell heterogeneity.

The B-cell mitogens lipopolysaccharide (LPS), Nocardia water-soluble mitogen (NWSM), and dextran sulfate (DxS) react with different subpopulations of B lymphocytes. Selective in vitro killing of cells responding to either LPS or NWSM has little effect on the in vitro response to the other mitogen, although the response to DxS is reduced in both cases. If, after selective in vitro killing, cells are injected into irradiated mice for 2-3 wk before measuring their in vitro mitogen responses, the same specificity pattern is seen. Thus, one is dealing with different B-cell subpopulations rather than different stages of maturation of a single population. Treatment with various alloantisera and complement before measuring the mitogen response to LPS and NWSM shows that (a) whereas all LPS response cells carry surface Ig, a subpopulation of NWSM responsive cells does not; (b) both LPS- and NWSM-responsive cells carry I-A antigens but might not I-E or I-J antigens; (c) all LPS-responsive cells carry I-C antigens, whereas approximately 25% of NWSM responsive cells do not: (d) there is a subpopulation of NWSM-responsive cells carrying neither surface Ig nor I-C antigens and resistant to anti-theta treatment.

Animals↗
PubMed1978

Activation of human B lymphocytes. IX. Modulation of antibody production by products of activated macrophages.

Human monocytes, after in vitro activation by mixed lymphocyte culture (MLC) supernatants produce a monokine (MK) that enhances the plaque-forming cell (PFC) response of pokeweed mitogen (PWM)-stimulated human B lymphocytes. Technical conditions and kinetics of MK production were established. Irradiation of monocytes (5000 rads) does not abolish MK production but heat-killed cells are unable to release the factor. Highly T cell-depleted monocyte populations still produced the PFC-enhancing factor. The same MK has an inconsistent enhancing effect on the PFC responses of lipopolysaccharide (LPS) and nocardia water-soluble mitogen (NWSM)-stimulated B cells. Other macrophage activators such as LPS, phytohemagglutinin (PHA), and latex particles failed to induce consistently the liberation of the PFC-enhancing MK. The target cell for the MK activity on PWM-stimulated B cells appears to be the B lymphocyte itself. These studies demonstrate that soluble monocyte products can have substantial modulatory effects on human B cell function.

Antibody Formation↗
PubMed1976

[Lymphocyte macrophage activation factor. Comparison of the mode of production in man and mice].

A macrophage activating factor (MAF) has been previously described in mixed lymphocyte cultures (MLC) between the donor and the recipient of a mouse skin allograft. This factor can render macrophages cytotoxic against mouse mastocytoma targert cells. The present work demonstrates the production of a similar factor in the human, using macrophages from uremic patients treated with peritoneal dialysis. There is, however, an apparent difference between mouse and human MAF. In the mouse the production of MAF in primary MLC is inconsistent, late and weak, while it is regularly found in large amounts in MLC between a donor and a recipient of a skin allograft. Conversely, in the human, MAF is consistently found in primary MLC as well as in MLC between two individuals previously sensitized to each other by a skin allograft followed by repeated white blood cell injections.

Animals↗
PubMed1975

Macrophage arming factor release by allografted mouse lymphocytes stimulated by phytohermgglutinin.

Spleen cells from a C57BL/6 mouse allografted with DBA/2 skin may release a macrophage arming factor when stimulated with phytohemagglutinin. This in vitro nonspecific release is observed only when the recipient cells are collected during a limited period preceding or coinciding with graft rejection. The phenomenon disappears if the skin allograft has been removed before cell collection. It appears if an i.v. injection of donor cells is given to the recipient after graft removal, on the day preceding cell collection. These data suggest that this in vitro apparently nonspecific macrophage arming factor release by phytohemagglutinin-stimulated recipient cells may in fact disclose a previous specific in vivo immune cell triggering by graft antigens.

Animals↗
PubMed1975

Macrophage cytotoxicity in the mouse immune response against a skin allograft.

Macrophage-rich peritoneal cell populations from C57BL/6 mice grafted with DBA/2 skin were found to be cytotoxic against 51Cr-labeled target cells from the donor strain. Normal peritoneal macrophages were also rendered cytotoxic by incubation with acellular supernatants of mixed lymphocyte cultures (MLC) between an allograft recipient and a donor mouse. Supernatants alone were not cytotoxic. The macrophage arming factor(s) was found in supernatants when the MLC was performed after more than 6 to 9 days following grafting. In order to produce MAF, sensitized lymphocytes must usually be stimulated in a specific way by donor type cells. The armed macrophage cytotoxicity was, however, not found to be specific in these experiments.

Animals↗