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Lipophosphoglycan (LPG) glycoconjugates from promastigotes of Leishmania were not able to induce the expression of the cytokine-inducible nitric oxide synthase (iNOS) by the murine macrophage cell line, J774. However, they synergize with interferon [Gamma] to stimulate the macrophages to express high levels of iNOS. This synergistic effect was critically time-dependent. Preincubation of J774 cells with the LPG glycans 4-18 h before stimulation with interferon [Gamma] resulted in a significant reduction in the expression of iNOS mRNA and of NO synthesis, compared with cells preincubated with culture medium alone. The regulatory effect on the induction of iNOS by LPG is located in the LPG phosphoglycan disaccharide backbone. Synthetic fragments of this backbone had a similar regulatory effect on NO synthesis. Further, the production of NO by activated macrophages in the present system was correlated directly with the leishmanicidal capacity of the cells. These data therefore demonstrate that LPG glycoconjugates have a profound effect on the survival of Leishmania parasites through their ability to regulate the expression of iNOS by macrophages.

A panel of peptide-specific murine CD4+ T-cell clones was tested for lymphokine secretion, antigenspecific cytolysis and CD3-mediated cytolysis. The data indicated an imperfect correlation between Th1/Th2 status with regard to antigen-specific cytolysis but also indicated that all the clones were cytotoxic when stimulated with anti-CD3 antibody. [ABSTRACT FROM AUTHOR]

Peritoneal macrophages from CBA mice incubated with recombinant murine turnout necrosis factor (TNF-α) are effective in killing the protozoa parasite Leishmania major in vitro. The leishmanicidal activity is directly correlated with the level of nitrite (NO2-) in the culture supernatants, The killing of intracellular parasites can be completely inhibited by L-NG-monomethyl arginine (L-NMMA), a specific inhibitor of the L-arginine:nitric oxide (NO) pathway, The level of NO2-, which is also a measurement of NO production, in the culture supernatant of TNF-α-activated macrophages can be progressively decreased to basal level with increasing concentrations of L-NMMA, but not with its D-enantiomer, D-NMMA. These data demonstrate that NO is an important effector mechanism in the TNF-α-induced macrophage killing of intracellular protozoa. [ABSTRACT FROM AUTHOR]

Mice injected in the footpad with carrageenin developed local inflammation which peaked at 48 hr. This delayed-type footpad swelling was significantly reduced in mice injected intraperitoneally (i.p.) with a specific nitric oxide (NO) synthase inhibitor, L-NGmonomethyl-arginine (L-NMMA). The draining lymph node (DLN) cells from mice injected 48 hr previously with carrageenin produced significantly higher levels of proliferation and interleukin-1 (IL-1), IL-2, IL-6 and interferon-γ (IFN-γ), but less IL-10, compared to cells from saline-injected controls, when stimulated with concanavalin A (Con A) in vitro. Treatment of the carrageenin-injected mice with L-NMMA had little effect on the proliferative response of the DLN cells, but significantly reduced the production of IL-1, IL-2, IL-6 and IFN-γ, and increased the secretion of IL-10. These data demonstrate that NO plays a significant role in local inflammation and the pattern of cytokines induced in this model. [ABSTRACT FROM AUTHOR]

BALB/c mice injected intraperitoneally with bacterial lipopolysaccharide (LPS) developed lethal septic shock. This was accompanied by significantly elevated concentrations of nitrite and nitrate in the plasma and expression of high levels of nitric oxide (NO) synthase activity in the lungs, heart, spleen and peritoneal macrophages. Mice pretreated with anti-turnout necrosis factor-α (TNF-α) monoclonal antibody or anti-interleukin-1β (IL-1β) polyclonal antibody were protected, in a dosedependent manner, from endotoxin-induced mortality. This effect was accompanied by a significant reduction in plasma levels of nitrite and nitrate. Antibody treatment also reduced the level of NO synthase activity in peritoneal macrophages, spleen and heart but had no effect on enzyme expression in the lung. These results demonstrate that TNF-α and IL-1β play an important role in the induction of NO following administration of LPS and in the development of endotoxin-induced shock. In addition, NO synthase activity is differentially expressed in various organs and this may not always require TNF-α and IL-1β. [ABSTRACT FROM AUTHOR]

The influence of different antigen delivery systems on antibody isotype and lymphokine profile has been investigated using influenza nucleoprotein as a model antigen system. Mice exposed to live or inactivated influenza virus produced antibody against whole virus or recombinant nucleoprotein (rNP), which was predominantly of the IgG2a isotype. Spleen or lymph node cells from these mice rapidly produced large amounts of interferon-γ (IFN-γ), but no detectable interleukin-5 (1L-5) when stimulated in vitro with specific antigen. In contrast, after primary immunization with rNP or p206229 in different adjuvants (CFA, quil A or alhydrogel), specific antibody was predominantly of the IgGl isotype and relatively lower amounts of IFN-γ but no IL-5 were detected following in vitro antigenic stimulation. Secondary immunization, however, resulted in detection of IgG2a antibodies and increased levels of IFN-γ. IL-5 was only detected after secondary immunization with peptide in adjuvant. Mice infected with aro A- Salmonella typhirnurium expressing NP produced antibody of both IgG1 and lgG2a isotypes and large amounts of IFN-γ and no IL-5, following in vitro antigenic stimulation, and therefore parallelled the pattern seen with whole virus more closely than that seen following primary immunization with protein or peptide in conventional adjuvants. The results suggest that the antigen delivery vehicle influences both quantitative and qualitative differences in the type of immune response elicited, which may be important in determining the potency of protective immunity induced. [ABSTRACT FROM AUTHOR]