Effect of individual and combination treatment with cytokines on expression of sialoadhesin by bone marrow macrophages.

We studied the effects of lipopolysaccharide, interferon-gamma, interleukin-1, or tumor necrosis factor-alpha and combination treatment with tumor necrosis factor-alpha and interleukin-1 or interferon-gamma on the expression of sialoadhesin receptors on the membrane of bone marrow macrophages, macrophage adherent ability, and production of nitric oxide by these cells. Sialoadhesin expression was evaluated by binding of macrophages to sheep erythrocytes labeled with radioactive (51)Cr. Treatment of bone marrow cells with interferon-gamma improved adhesive properties of macrophages, but did not modulate expression of sialoadhesin. Interleukin-1 and tumor necrosis factor-alpha had no effect on the test parameters. Combination treatment with these cytokines enhanced binding of sheep erythrocytes to macrophages. Administration of lipopolysaccharide or combination treatment with interferon-gamma and tumor necrosis factor-alpha increased the count of macrophages adhering to plastic and stimulated expression of sialoadhesin. Combination treatment with interferon-gamma and tumor necrosis factor-alpha stimulated production of nitric oxide by bone marrow macrophages. Blockade of nitric oxide synthesis had no effect on adhesive properties of macrophages and expression of sialoadhesin.

Gr-1+ myeloid cells derived from tumor-bearing mice inhibit primary T cell activation induced through CD3/CD28 costimulation.

Activation of T cells is a necessary step in the development of a specific antitumor immune response. In the present study, we evaluated the ability of Gr-1+ myeloid cells, derived from the bone marrow or spleen of tumor-bearing mice, to inhibit CD3/CD28-mediated T cell activation. Using flow cytometry, we found that growth of a murine colon carcinoma (MCA-26) induces a significant increase in the number of Gr-1+ and Gr-1+/Mac-1+ myeloid cells in both bone marrow and spleen of the tumor host. The proliferative response of T cells was dramatically decreased when naive T cells were activated by anti-CD3 and anti-CD28 Abs in the presence of a myeloid-enriched cell fraction derived from spleen or bone marrow of tumor-bearing mice vs the bone marrow of naive mice. Reversal of the inhibitory effect could be achieved by adding a combination of MnTBAP (manganese [III] tetrakis [4-benzoic acid]) porphyrin and l -NMMA (NG-monomethyl-l -arginine), a superoxide dismutase mimetic and inducible NO synthase inhibitor, respectively, or by depletion of the Gr-1-positive cells. IFN-gamma, which is endogenously produced by CD3/CD28-stimulated naive T cells, is involved in induction of the inhibitory activity of myeloid cells. Importantly, when T cells pre-activated with anti-CD3 Abs were used as responder cells, the bone marrow- or spleen-derived Gr-1+ myeloid cells were unable to suppress CD3/CD28-induced T cell proliferation. Our findings suggest that one mechanism by which an increased number of immune suppressive Gr-1+ cells can induce T cell unresponsiveness or immune tolerance in tumor hosts could be through peroxynitrite production upon primary T cell activation.

Sialoadhesin expression by bone marrow macrophages derived from Ehrlich-tumor-bearing mice.

Sialoadhesin (sheep erythrocyte receptor, SER) is a macrophage-restricted adhesion molecule that binds certain sialylated ligands. It is borne by bone marrow stromal macrophages, promoting the interaction with developing myeloid cells, and by a subset of tissue macrophages involved in antigen presentation and activation of tumor-reactive T cells. The expression of sialoadhesin on SER+ macrophages is not constitutive but requires the continuous supply of a sialoadhesin-inducing serum factor. Tumor growth is often associated with marked alterations of myelopoiesis and impairment of T cell activation; yet the expression of sialoadhesin in macrophages derived from tumor bearers has not been addressed. The aim of this study was to assess whether Ehrlich tumor (ET) - a murine mammary carcinoma - growth may modify the sialoadhesin expression by bone marrow macrophages and/or sialoadhesin-inducing activity in ET-bearing sera. Moreover, putative functional sialoadhesin inhibitors produced by ET cells were tested. The results indicate that bone marrow cells from ET bearers show a seven- to eight-fold decrease in SER+ cells as detected by flow cytometry. This is accompanied by an overall decrease in sheep erythrocyte binding to tumor-bearer-derived bone marrow cells, but also by lower numbers of plastic-adherent cells. Functional sialoadhesin expression is preserved at the single-cell level and no inhibitors are found in ET-bearing sera or ET cell culture supernatants. Tumor progression does not impair the sialoadhesin-inducing activity of ET-bearing sera, or the ability of SER- macrophages (e.g. peritoneal macrophages) to respond to such an induction. In conclusion, while SER+ macrophages are greatly decreased in bone marrow from ET bearers, this is not due to a down-regulation of sialoadhesin expression, nor to an impairment of sialoadhesin-inducing factor or to the presence of sialoadhesin-binding moieties of tumor origin, but, more likely, to a decrease of fully mature macrophages.

[The possible glyciram stimulation of bone marrow hematopoiesis under cytostatic blood depression]. / O vozmozhnosti stimuliatsii glitsiramom kostnomozgovogo krovetvoreniia v usloviiakh tsitostaticheskoi gemodepressii.

The present study was undertaken to examine whether glycyrram orally given can correct blood abnormalities caused by a single maximal tolerable dose of fluorouracil. Glycyrram was demonstrated to stimulate the recovery of granulocytic and erythroid populations of bone marrow hemopoiesis. The stimulating effect of glycyrram was associated with its activating action on the function of hemopoietic microenvironmental cells.

[The effect of cells presenting the erythroblast antigen on the natural suppressor activity of nonadhesive bone marrow cells]. / Vliianie kletok, nesushchikh antigen eritroblastov, na estestvennuiu supressornuiu aktivnost' neadgezivnykh kletok kostnogo mozga.

Concanavalin A-induced proliferation of spleen cells of C57B1/6 mice was inhibited by syngeneic normal bone marrow cells. Elimination of Ag-Eb-positive cells by panning was shown to result in markedly reduced inhibitory activity of bone marrow cells. To evaluate the role of Ag-Eb in natural suppressor activity, bone marrow cells were preincubated with different dilutions of MAE-15 monoclonal antibody and then added to spleen cells. The inhibitory effect of bone marrow cells decreased with the increasing concentration of the monoclonal antibody in a dose-dependent manner and nearly disappeared at a concentration of MAE-15 of 150 m micrograms/ml and 300 m micrograms/ml. In control experiments, bone marrow cells were preincubated with antibodies non-reactive with Ag-Eb under the same conditions. It is concluded that the decrease of natural suppressor activity after incubation of bone marrow cells with MAE-15 monoclonal antibody is specific for anti-Ag-Eb antibodies.

[Suppressor activity of bone marrow and spleen cells in C57Bl/6 mice during carcinogenesis induced by 7,12-dimethylbenz(a)anthracene]. / Supressornaia aktivnost' kletok kostnogo mozga i selezenki myshei linii C57Bl/6 pri kantserogeneze, indutsirovannom 7,12-dimetil- benz(a)antratsenom.

The nonspecific suppressor activity of bone marrow cells (BMC) and spleen cells (SC) of C57B1/6 mice was studied at 7,12-dimethylbenz(a)anthracene-induced carcinogenesis. It is established that in the latent period of the tumour development and with its appearance the suppressor activity of BMC decreases, while SC-increases. The activity of the BMC suppressor factor which is determined by the inhibition of proliferation of mastocytoma P-815 cells in vitro did not change significantly.

[The activity of nonspecific bone marrow and spleen suppressors in the latent period of tumor growth]. / Aktivnost' nespetsificheskikh supressorov kostnogo mozga i selezenki v latentnyi period opukholevogo rosta.

Female A/Sn mice aged 2-3 and 11-14 months (with spontaneous adenocarcinomas of the mammary gland and tumor-free) and C57Bl/6 mice were followed after treatment with DMBA. Suppressor cells were tested for the ability to inhibit in vivo antibody responses to sheep erythrocytes by adoptively syngeneically transferred cells. It was demonstrated that the activity of nonspecific suppressors of the bone marrow and spleen increases considerably in the precancer period.