Expression of zeta molecules is decreased in NK cells from HIV-infected patients.

Cytolysis by natural killer (NK) cells is impaired in HIV infection. We investigated whether the expression of zeta (zeta) molecules, essential elements of signalling initiated upon ligation of, e.g., CD16, is reduced and if so, whether this reduction could be involved in defective cytolysis. FACS analysis revealed significantly lower levels of zeta in NK cells from AIDS patients compared to cells from patients without AIDS and healthy controls. CD16-dependent cytolysis by NK cells correlated with expression of zeta molecules and CD16, the latter possibly related to zeta expression. No correlation was observed between CD16-independent cytolysis and zeta expression. Reduced expression of zeta molecules by NK cells from HIV-infected patients thus correlates with disease progression and may, in part, explain the defective cytolysis by these cells.

Decreased expression of zeta molecules by T lymphocytes is correlated with disease progression in human immunodeficiency virus-infected persons.

In human immunodeficiency virus type 1 (HIV-1) infection, functional activities of T lymphocytes are impaired. Analogous to tumor-infiltrating T lymphocytes from cancer patients, in whom poor proliferative responses are associated with fewer zeta molecules, this study compared expression of CD3zeta molecules by T lymphocytes from HIV-infected persons and healthy controls. Flow cytometry and immunoblotting revealed significantly diminished zeta expression by CD3, CD4, and CD8 T lymphocytes from AIDS patients but not from persons without AIDS. zeta-mRNA levels were also decreased in cells from AIDS patients. CD3zeta expression correlated significantly with CD4 cell counts and HIV-1 RNA levels; impaired expression of CD3zeta molecules appeared to be reversible upon virus load reduction following highly active antiretroviral treatment (HAART). Thus, reduced expression of CD3zeta molecules by T lymphocytes from HIV-infected persons correlates with disease status. Investigations into CD3zeta expression by subpopulations of peripheral T lymphocytes and by T lymphocytes in lymphoid tissues will contribute to the understanding of immune reconstitution of HIV-infected patients following HAART.

Reduced toxoplasmastatic activity of monocytes from AIDS patients: a role for granulocyte-macrophage colony-stimulating factor.

In the present study the role of granulocyte-macrophage colony stimulating factor (GM-CSF) in the reduced toxoplasmastatic activity of monocytes was investigated in patients with acquired immunodeficiency syndrome (AIDS). The secretion of GM-CSF by non-stimulated monocytes and by Toxoplasma gondii-infected monocytes from AIDS patients did not differ from that of healthy individuals. Furthermore, GM-CSF was not detected in sera from AIDS patients and healthy individuals. However, upon stimulation with lipopolysaccharide (LPS), monocytes from AIDS patients released significantly more GM-CSF than those from healthy individuals. Incubation of monocytes from AIDS patients with polyclonal antibodies against GM-CSF restored their inhibitory activity against T. gondii. On the basis of the present and earlier results the putative mechanism of reduced toxoplasmastatic activity of monocytes from AIDS patients may be as follows: upon stimulation with human immunodeficiency virus (HIV) the increased synthesis of GM-CSF by monocytes stimulates the production of prostaglandin E2 (PGE2) which, in turn, impairs the toxoplasmastatic activity of these cells.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) reduces toxoplasmastatic activity of human monocytes via induction of prostaglandin E2 (PGE2).

In this study we investigated the effect of human GM-CSF on the toxoplasmastatic activity and release of H2O2 and PGE2 by human monocytes. Incubation of monocytes from healthy controls with GM-CSF resulted in a dose-dependent reduction of toxoplasmastatic activity and a decrease in H2O2 production. Furthermore GM-CSF-treated monocytes released more PGE2 than untreated cells. To investigate the role of PGE2 in the reduced toxoplasmastatic activity of GM-CSF-treated monocytes, these cells were incubated with indomethacin. This resulted in a reduction of PGE2 release and restoration of toxoplasmastatic activity of monocytes treated with GM-CSF. GM-CSF reduces the toxoplasmastatic activity of monocytes via production of PGE2.

Reduced toxoplasmastatic activity of monocytes and monocyte-derived macrophages from AIDS patients is mediated via prostaglandin E2.

OBJECTIVE: To establish the role of prostaglandin E2 (PGE2) formed and released by monocytes and monocyte-derived macrophages (MDM) in the reduced toxoplasmastatic activity of these cells. DESIGN: Determination of PGE2 levels in the serum of AIDS patients, the release of PGE2 by monocytes and MDM from AIDS patients, the toxoplasmastatic activity of these cells and the effect of indomethacin, an inhibitor of PGE2 synthesis, on this cell function. SETTING: Laboratory of Cellular Immunology of the Department of Infectious Diseases, University Hospital, Leiden. PARTICIPANTS: Twenty-six AIDS patients. Healthy blood donors served as controls. RESULTS: The concentration of PGE2 in the serum from AIDS patients was significantly higher compared with serum from controls. Non-stimulated monocytes and lipopolysaccharide-stimulated monocytes and MDM from AIDS patients released significantly more PGE2 than corresponding cells from the controls. The proliferation of Toxoplasma gondii in monocytes and MDM from AIDS patients was significantly higher than in the respective cells from controls. Preincubation of these cells with indomethacin resulted in a decreased proliferation of T. gondii in non-activated monocytes and MDM and in interferon-gamma-activated MDM from AIDS patients. Preincubation of monocytes from healthy donors with PGE2 resulted in a dose-dependent increase of Toxoplasma proliferation which confirms that PGE2 can reduce the toxoplasmastatic activity of monocytes. CONCLUSION: PGE2 is involved in the reduced toxoplasmastatic activity of monocytes and MDM from AIDS patients.

Effect of IFN-gamma on the proliferation of Toxoplasma gondii in monocytes and monocyte-derived macrophages from AIDS patients.

This study was undertaken to determine whether the activity of monocytes and monocyte-derived macrophages (MDM) from acquired immune deficiency syndrome (AIDS) patients against Toxoplasma gondii is altered and whether this activity can be modulated by recombinant interferon-gamma (rIFN-gamma). Untreated and rIFN-gamma-treated monocytes or MDM from AIDS patients and from healthy controls were infected with T. gondii and the proliferation of these protozoa was determined. The H2O2 release by monocytes from AIDS patients and healthy controls was measured upon stimulation with phorbol myristate acetate (PMA) and formyl methionyl leucyl phenylalanine (FMLP). Monocytes from AIDS patients exhibited significantly lower toxoplasmastic activity compared to monocytes from healthy controls. The H2O2 release by monocytes from AIDS patients was also diminished. Incubation of monocytes from AIDS patients with rIFN-gamma for 2 days, but not 1 day, restored their toxoplasmastatic activity. The rate of proliferation of T. gondii was higher in MDM from AIDS patients than in MDM from healthy controls. Treatment of MDM from AIDS patients with rIFN-gamma for 1, 2 or 3 days resulted in partial inhibition of the proliferation of T. gondii. Collectively, these results demonstrate that the reduced toxoplasmastatic activity of monocytes and MDM from AIDS patients can be enhanced by in vitro treatment with rIFN-gamma, which supports the clinical use of rIFN-gamma for the treatment of opportunistic infections in these patients.

Interleukin-8 enhances nonoxidative intracellular killing of Mycobacterium fortuitum by human granulocytes.

The results of this study show that recombinant interleukin-8 (IL-8) enhances the intracellular killing of Mycobacterium fortuitum by human granulocytes. This chemokine did not stimulate the phagocytosis of M. fortuitum by granulocytes at various bacterium-to-cell ratios. The killing process was not affected by the NADPH oxidase inhibitor diphenyleneiodonium bisulfate, which indicates that recombinant IL-8 stimulates oxygen-independent mycobactericidal mechanisms of granulocytes. IL-8 did not stimulate H2O2 production in granulocytes but primed the cells for enhanced H2O2 production upon stimulation with preopsonized M. fortuitum. In sum, the chemokine IL-8 not only is involved in the recruitment of granulocytes to the site of infection but also facilitates the elimination of microorganisms by increasing the efficiency of the bactericidal activity of granulocytes.

Interferon-gamma activates the oxidative killing of Candida albicans by human granulocytes.

Although granulocytes are essential for the resistance against infections with Candida albicans, these cells do not kill the ingested yeast optimally. Various cytokines can enhance functional activities of granulocytes, but until now only interferon-gamma (IFN-gamma) has been applied more widely, namely in patients with chronic granulomatous disease. Since it is not certain whether IFN-gamma is able to enhance the candidacidal activity of granulocytes the present study was undertaken. Human granulocytes incubated with various concentrations of recombinant human IFN-gamma (rIFN-gamma) were studied for the phagocytosis and intracellular killing of C. albicans and their oxygen metabolism after stimulation with opsonized Candida. Results showed a small increase in the rate of phagocytosis and a dose-dependent increase of the intracellular killing of C. albicans and the production of H2O2. The increased candidacidal activity and H2O2 production by rIFN-gamma-stimulated granulocytes were inhibited by diphenylene iodonium (DPI). From these results it is concluded that the increased candidacidal activity of granulocytes activated by rIFN-gamma is caused by the increased production of reactive oxygen radicals.

Impaired phagocytosis of Staphylococcus aureus by granulocytes and monocytes of AIDS patients.

In the present study the microbicidal activities of granulocytes and monocytes from AIDS patients (CDC group IV) were assessed and compared with those of healthy controls. The phagocytosis and intracellular killing of Staphylococcus aureus by patient and control cells were measured using a method in which the rate of intracellular killing can be assessed independently of the rate of phagocytosis. Both granulocytes and monocytes of AIDS patients showed a decreased phagocytosis of S. aureus in comparison to phagocytes of healthy individuals. The rates of intracellular killing of S. aureus by granulocytes and monocytes did not differ significantly between these patients with late-stage HIV infection and controls.