Production of interferons by bovine and ovine cell lines infected with Theileria annulata or Theileria parva

Three bovine cell lines and four ovine cell lines infected with Theileria parva or Theileria annulata were examined for the production of interferon (IFN). Biologically active IFN was detected in the tissue culture supernatants of four of the cell lines. Only one, a bovine cell line infected with T. parva, produced IFN-gamma as measured by specific neutralization with a monoclonal antibody to bovine IFN-gamma. This observation was confirmed by analysing RNA from the cell lines on Northern blots using an IFN-gamma cDNA probe. The other three cell lines which produced IFN were infected with T. annulata. The IFN produced by those lines was not IFN-gamma.     

Cytokines inhibit the development of trophozoite-infected cells of Theileria annulata and Theileria parva but enhance the proliferation of macroschizont-infected cell lines

The following bovine (Bo) and human (Hu) cytokines--Bo rTNF-a, Bo rIFN-g, Hu IFN-a, Hu rIL-1, Hu rIL-2--significantly inhibited the in vitro development of trophozoite-infected cells of three stocks of Theileria annulata and of Theileria parva (Muguga). However, none of these cytokines inhibited the proliferation of established T. annulata or T. parva macroschizont-infected cell lines. Indeed, Bo rTNF-a and Hu rIL-2 consistently enhanced the proliferation of macroschizont-infected cell lines of both species and the blastogenesis of uninfected lymphocytes in trophozoite-infected cultures. These results suggest that cytokines could help in resistance to challenge infections by preventing the further development of trophozoite-infected cells but provide no evidence that any of the above cytokines directly help to resolve primary infections by inhibiting the growth of macroschizont-infected cells. These findings also suggest that both TNF-a and IL-2 could play a role in the pathogenesis of Theileria infections by promoting the proliferation of macroschizont-infected cells and the associated lymphoid hyperplasia.     

Bovine lymphocyte antigens (BoLA) of bovine lymphocytes and derived lymphoblastoid lines transformed by Theileria parva and Theileria annulata

Summary The BoLA phenotypes of lymphocytes from seven cattle have been compared with those of 19 lymphoblastoid cell lines derived from them by infection in vitro with either Theileria parva or T. annulata. Two long-established lines were also studied. In all cases except one, the BoLA phenotypes of the lymphoblastoid lines were identical with those of the original animal from whose lymphocytes they were derived. The one exception was a chimeric twin where a minor population appeared to have been transformed by T. parva. The antigens present on this line were present in the parents of the chimera, but not detectable in its own peripheral blood. The implications of these results as they relate to the use of these cell lines in immunizing cattle against East Coast fever and tropical theileriosis are discussed.     

Bovine mononuclear cell lines transformed by Theileria parva or Theileria annulata express different subpopulation markers

Summary Bovine mononuclear cell lines infected with the protozoan parasites Theileria annulata and T. parva have been studied with a panel of monoclonal antibodies reacting with bovine lymphocyte subpopulation markers. All infected lines are MHC class II positive, though the amount of class II antigen expressed varied between lines, and within individual lines there was variation in the proportion of positive cells from 100% with many, to less than 10%. All lines were negative for a macrophage/monocyte marker and for surface IgM. The T. parva lines tested were all positive for BoT4 or BoT8 or both, whereas T. annulata lines were uniformly negative for both of these markers. These results suggest that the two parasites preferentially infect different lymphocyte subpopulations.     

Nitric oxide modulates interleukin-1beta and tumour necrosis factor-alpha synthesis, and disease regression by alveolar macrophages in pulmonary tuberculosis

Pretreatment with nitric oxide synthase (NOS) inhibitors profoundly increases mortality, bacterial burden and pathological tissue damage in mice infected with Mycobacterium tuberculosis. Nitric oxide (NO) production is enhanced in alveolar macrophages (AM) of tuberculosis (TB) patients. Interleukin (IL)-1beta and tumour necrosis factor (TNF)-alpha released from AM are involved in the immune response to mycobacterial infection. The aim of the present study was to examine whether NO is implicated in IL-1beta and TNF-alpha synthesis by AM and related to the resolution of disease activity in TB patients. Purified AM were retrieved by bronchoalveolar lavage from TB patients and normal subjects, and cultured in the presence or absence of a NO inhibitor, NG-monomethyl-L-arginine (L-NMMA). The release of IL-1beta and TNF-alpha, and their mRNA expression were determined by enzyme-linked immunosorbent assay (ELISA) and northern analysis, respectively. The level of nitrite released into the culture medium was determined. The rate of disease regression was evaluated by serial chest radiography. The release of nitrite, IL-1beta and TNF-alpha was much greater from AM of TB patients than normal subjects. NG-monomethyl-L-arginine inhibited the production of nitrite as well as IL-1beta and TNF-alpha in TB patients. The mRNA expression for IL-1beta and TNF-alpha was upregulated in TB patients and was depressed by L-NMMA. Immunocytochemistry using a monoclonal antibody against nuclear factor-kappaB (NF-kappaB) subunit p65 showed NF-kappaB was highly expressed and translocated to the nuclei of AM in TB patients, and was inhibited by L-NMMA. An inhibition of NF-kappaB by pyrrolidine dithiocarbamate attenuated IL-1beta and TNF-alpha synthesis. More generation of NO from cultured AM increased the disease regression in TB patients. We conclude that the enhanced NO generation by AM of TB patients may play an autoregulatory role in amplifying the synthesis of pro-inflammatory cytokines, probably through the activation of NF-kappaB. Nitric oxide may also play an important role in resistance to M. tuberculosis infection.     

Cytotoxicity of activated rat macrophages against syngeneic islet cells is arginine-dependent,correlates with citrulline and nitrite concentrations and is identical to lysis by the nitric oxide donor nitroprusside

Summary Lysis of rat islet cells by syngeneic activated macrophages in vitro can be completely inhibited by the nitric oxide-synthase-inhibitor N^G-methyl-l-arginine. This inhibition can be reversed by an excess of l-arginine. Time-dependent lysis of islet cells by activated macrophages is accompanied by increasing concentrations of nitrite and citrulline in the culture medium both of which are measures of nitric oxide formation derived from l-arginine. Lysis of isolated islet cells and disintegration of isolated whole islets is also obtained within 15 h by culture in the presence of the nitric oxide generating vasodilator sodium nitroprusside. We thus conclude that nitric oxide is extremely toxic for islet cells and that nitric oxide alone and in the absence of other macrophage-generated potentially toxic products can rapidly and completely kill islet cells.     

Trypanosoma cruzi upregulates nitric oxide release by IFN-γ-preactivated macrophages, limiting cell infection independently of the respiratory burst

The relationship between nitric oxide (N = O) produced by mouse peritoneal macrophages (MPM) and Trypanosoma cruzi infection is still poorly understood. The conditions of MPM activation by gamma-interferon (IFN-γ) to trigger a N = O-dependent trypanocidal activity, as well as the effect of parasite infection or of reactive oxygen species (ROS) inhibitors on the N = O release were studied. T. cruzi infection occurring after a previous 24 h MPM activation induced an enhancement of nitrite levels (the stable degradation product of N = O) in cell supernatants; both the percentage of infected MPM and the number of amastigotes per infected cell were decreased in comparison to infected but non-activated MPM. Addition of superoxide dismutase or catalase to non-infected but activated MPM increased the nitrite levels; these were not detectable when L-arginine inhibitors were added together with ROS inhibitors. The latter had no effect on infection nor on nitrite levels when infection occurred after pre-activation, and induced only a weak nitrite release when infection took place before MPM activation. Altogether, these results support the involvement of N = O in the inhibition of T. cruzi infection by IFN-γ-preactivated macrophages, together with the upregulation of N = O release by T. cruzi infection independently of the respiratory burst.     

Relationship between granulocyte macrophage-colony stimulating factor, tumour necrosis factor-α and Trypanosoma cruzi infection of murine macrophages

Gamma interferon (IFN-γ)-activated macrophages control Trypanosoma cruzi infection via nitric oxide (NO), recently recognized as a major effector molecule. Granulocyte macrophage-colony stimulating factor (GM-CSF) is a multipotent cytokine secreted by macrophages and many other cells. It induces the production of tumour necrosis factor alpha (TNF-α), another cytokine also secreted by macrophages and involved in the control of T. cruzi infection. However, no data are available on the relationship between GM-CSF, TNF-a and NO produced by macrophages activated by IFN-γ and infected with T. cruzi. To highlight this relationship, mouse peritoneal macrophages (MPM) and two c-myc retrovirus-induced macrophage cell lines (9.1.1 and BMM8), respectively characterized by a constitutive and an inducible production of GM-CSF, were activated with I FN–γ and/or GM-CSF and infected with T. cruzi. Our results indicate that T. cruzi upregulates GM-CSF release from MPM and from the two macrophage cell lines, activated (or not) by IFN-γ. A high autocrine production of GM-CSF or an exogenous supply of GM-CSF is correlated with an enhanced release of TNF-α and NO, inducing an improved control of T. cruzi infection by IFN-γ-activated MPM.