Effect of stimulation of human macrophages on intracellular survival of Mycobacterium bovis Bacillus Calmette-Guerin. Evaluation with a mycobacterial reporter strain.

The mechanisms through which immune and inflammatory responses stimulate the expression of antimycobacterial activity by human macrophages remain poorly defined. To study this question, we developed a method permitting the rapid quantification of viable mycobacteria, based on the detection of luciferase activity expressed by a Mycobacterium bovis Bacillus Calmette-Guerin (BCG) reporter strain, and used this approach to evaluate mycobacterial survival in human monocyte-derived macrophages following stimulation with cytokines and through crosslinking of costimulatory molecules expressed on the cell surface. Modest proliferation, followed by persistence of mycobacteria, was observed in unpretreated macrophages as assessed both by measurement of luciferase activity and by the evaluation of colony forming units. Of the 19 cytokines tested, only granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) were found to improve the mycobactericidal activity of monocyte-derived macrophages. In both cases, this effect was observed only when macrophages were pretreated with the cytokines prior to infection. In contrast, pretreatment of human macrophages with interferon-gamma, either alone or in combination with other mediators (including tumor necrosis factor-alpha and 1,25[OH]2-vitamin D3), did not improve mycobacterial killing. The stimulation of macrophages through several different costimulatory molecules known to participate in macrophage-lymphocyte interactions (CD4, CD40, CD45, CD86, CD95 [Fas/Apo-1]) also failed to improve mycobactericidal activity. This study shows that GM-CSF and IL-3, cytokines whose receptors are known to share a common subunit and to use common second messengers, may contribute to the stimulation of mycobactericidal activity in humans. The ability to rapidly screen the effects of different macrophage stimuli on mycobacterial survival through the detection of luciferase activity should help define additional signals required for optimal antimycobacterial responses.

Identification of genetic loci implicated in the survival of Mycobacterium smegmatis in human mononuclear phagocytes.

A luminescence-based procedure that permits the rapid evaluation of the survival of mycobacteria within mononuclear phagocytes was developed and used to screen insertional mutants of Mycobacterium smegmatis for their ability to survive in human monocyte-derived macrophages. Among the 5000 mutants tested, eight mutants were identified that demonstrated impaired intracellular survival in human macrophages but that grew normally in the absence of cells. For each mutant, a portion of the gene interrupted by the transposition event was amplified by ligand-mediated PCR and sequenced. In all cases, the existence of homologous genes of as yet unknown function were identified in the Mycobacterium tuberculosis genome. Complementation of the mutant mycobacterial strains with cosmids containing the homologous loci from M. tuberculosis restored normal intracellular growth in three of the four mutants tested, supporting the idea that these loci contain genes that are important for intracellular survival. This study demonstrates the feasibility of directly screening mutant mycobacterial strains to identify genes coding for activities necessary for the intracellular survival in human mononuclear phagocytes, an important initial step in the identification of potential targets for new therapeutic agents.

A reliable amplification technique for the characterization of genomic DNA sequences flanking insertion sequences.

A simple and efficient ligation-mediated PCR (LMPCR) is described for amplifying DNA adjacent to known sequences. The method uses one primer specific for the known sequence and a second specific for a synthetic linker ligated to restricted genomic DNA. Perkin-Elmer AmpliTaq Gold polymerase is used to minimize non-specific primer annealing and amplification. This LMPCR method was successfully applied to isolate DNA sequences flanking mobile elements present in mycobacterial mutants generated by transposon mutagenesis.

Different modulation by histamine of IL-4 and interferon-gamma (IFN-gamma) release according to the phenotype of human Th0, Th1 and Th2 clones.

Histamine, an important inflammatory mediator in allergic diseases and asthma, has been reported to have modulator effects on T cells, suggesting that the bronchial microenvironment may regulate the function of resident T cells. We examined the effect of histamine on the release of the Th2-associated cytokines IL-4 and IL-5 and the Th1-associated cytokine IFN-gamma by 30 CD4+ T cell clones from peripheral blood or bronchial biopsy of one atopic subject. Based on the IL-4/IFN-gamma ratio, the clones were ascribed to the Th2 (ratio > 1), Th0 (ratio > or = 0.1 and < or = 1) or Th1 (ratio < 0.1) phenotype. Histamine inhibited IFN-gamma production by Th1-like cells (P < 0.02, Kruskall-Wallis), especially from bronchial biopsy, but had no effect on IL-4 release. Regarding Th0 clones, histamine inhibited IL-4 production (P < 0.02) in a dose-dependent manner and slightly inhibited IFN-gamma production, but had no effect on Th2-like cells. Histamine had a heterogeneous and insignificant effect on IL-5 production. The H2-receptor antagonist ranitidine completely reversed the inhibition of IL-4 and IFN-gamma production, whereas the agonist dimaprit mimicked this effect. In contrast, H1- and H3-receptor agonists and antagonists had no significant effect. These data demonstrate that histamine has different effects on IL-4 and IFN-gamma release by T helper cells according to their phenotype via H2-receptors. This study extends the immunomodulatory effects of histamine which may contribute to the perpetuation of airway inflammation in asthma.

Nicotine does not modulate IL-4 and interferon-gamma release from peripheral blood mononuclear cells and T cell clones activated by phorbol myristate acetate and calcium ionophore.

Tobacco smoking induces an increased nonspecific IgE response. IgE synthesis is controlled by IL-4 and IFN-gamma. The effect of nicotine (10(-10) to 10(-5) M), one of the major components of tobacco smoke, were studied on IL-4 and IFN-gamma release by peripheral blood mononuclear cells from 12 allergic patients and 12 nonallergic subjects and 16 T cell clones stimulated by nonspecific agonists (phorbol myristate acetate and calcium ionophore). The release of IL-4 and IFN-gamma was measured by ELISA in supernatants after a 48-hour culture. Nicotine did not modify IL-4 and IFN-gamma release by peripheral blood mononuclear cells or T cell clones. The effects of tobacco smoke on IgE production are unlikely to change in the T cell phenotype by nicotine.

Effect of monoclonal and polyclonal antibodies against conjugated neurotransmitter on experimental venous thrombosis.

Vasomotoricity in veins is largely controlled by the sympathetic nervous system. Norepinephrine and acetylcholine modulate the vasoconstrictor effect mediated by alpha-adrenergic receptors. Our objective was to study the role of local vasomotoricity in venous thrombosis, and particularly to determine some of the factors regulating it. Although no attempt has been described until now, polyclonal and monoclonal antibodies against L-dihydroxyphenylalanine, acetylcholine, and dopamine were administered in an experimental model of venous thrombosis. In view of the rather high specific antibody recognition for each compound, the presence of endogenous epitopes of L-dopa-like molecules and acetylcholine-like molecules in the circulation can be postulated. The results of this study may open an important new approach in the treatment of vascular diseases.

Seasonal variations of interleukin-4 and interferon-gamma release by peripheral blood mononuclear cells from atopic subjects stimulated by polyclonal activators.

IgE synthesis is controlled by interleukin (IL)-4 and interferon (IFN)-gamma, but there is heterogeneity in the IL-4 response depending on the sensitization of patients and natural allergen exposure. In patients sensitized to various allergens, we studied the synthesis of IL-4, IFN-gamma, and IgE to determine to what extent their in vitro immune response may be influenced by pollen season, depending on their sensitization. We studied 12 nonallergic individuals, seven patients sensitized to cypress pollen, 12 sensitized to grass pollen, 14 sensitized to several pollens, and 42 patients with polysensitization. The release of IL-4 and IFN-gamma from peripheral blood mononuclear cells stimulated by polyclonal agents (calcium ionophore A23187 and phorbol myristate acetate) was measured by ELISA. The spontaneous and IL-4-induced release of IgE was measured by ELISA. In patients with cypress pollen allergy, IL-4 and IgE release were significantly lower than in patients with other allergies. In the pollen-sensitized group, IL-4 and IgE release were significantly higher during the pollen season than out of it. No variation in IL-4 or IgE release was observed in the polysensitized group. IFN-gamma production was not affected by the pollen season. These data show that the seasonal variations of IL-4 and IgE synthesis differ according to the sensitization of patients.

Differences in IL-4 release by PBMC are related with heterogeneity of atopy.

Atopy is heterogeneous and the IgE immune response of patients allergic to a single allergen (monosensitized) differs from that of those allergic to multiple allergens (polysensitized). Since interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) regulate human IgE synthesis in vitro, we determined whether cytokines may be involved in the heterogeneity of atopy by comparing the serum IgE and sCD23 titres to the cytokine profile of T lymphocytes from 44 atopic patients (13 mono- and 31 polysensitized) and seven non-atopic subjects. Monosensitized patients were allergic to grass or cypress pollens or house dust mites, and polysensitized ones to many pollen species (n = 5) or many allergens (n = 26). Total serum IgE was lower in the control group than in both atopic groups and in the monosensitized group than in the polysensitized one. IgE immunoblots to orchard grass pollen and house dust mites were less heterogeneous in the monosensitized group than in the polysensitized one. IL-4 production by in vitro-activated peripheral blood mononuclear cells (PBMC) was significantly higher in the polysensitized group than in the monosensitized, and marginal in the control group. In contrast, IFN-gamma production was strongly reduced in both atopic groups, and IL-2 production comparable in the three groups. IgE and soluble CD23 (sCD23) release was higher in the atopic groups than in the control, and higher in the polysensitized group than in the monosensitized one. This study shows that PBMC of mono- and polysensitized subjects have a different IL-4 and sCD23 profile and suggests that human beings may be classified into high and low IgE responders on the basis of IL-4 production.