Secondhand smoke induces allergic sensitization in mice.

Epidemiological studies have suggested increased prevalence of atopy in children of maternal smokers. Although secondhand smoke or environmental tobacco smoke (ETS) has been shown to augment allergic responses, its role in atopic sensitization is still controversial. We studied whether ETS could initiate a Th2 response and thus induce primary allergic sensitization. Mice were exposed for 10 consecutive days to either 1% aerosolized OVA, ETS (5 cigarettes), or both ETS and OVA. C57BL/6 mice receiving both ETS and OVA developed OVA-specific IgE and IgG1, 12, 14, and 25 days after the initial exposure, whereas those receiving OVA alone did not. Thirty days after the initial challenge (20 days after its completion), mice were re-exposed to OVA. Bronchoalveolar lavage performed 24 h later revealed an influx of eosinophils in the group initially challenged with both ETS and OVA, but not in those exposed to ETS alone or OVA alone. Increases in IL-5, GM-CSF, and IL-2 were observed in bronchoalveolar lavage from this OVA/ETS-exposed group, whereas IFN-gamma levels were significantly inhibited. These results suggest that ETS can induce allergic sensitization to a normally harmless Ag, and they may explain why secondhand smoke is a major risk factor for the development of allergy in children.

An IgG antiprothrombin antibody enhances prothrombin binding to damaged endothelial cells and shortens plasma coagulation times.

OBJECTIVE: To test the hypothesis that some lupus anticoagulants are antiprothrombin antibodies, and that such antibodies enhance prothrombin binding to endothelial cells (EC) and thus promote clotting on the cell surface. METHODS: We generated a monoclonal antiprothrombin antibody (designated IS6) from a patient with primary antiphospholipid syndrome (APS). The antibody was analyzed for its binding properties, lupus anticoagulant activity, and pathophysiologic activity, using an EC-based plasma coagulation assay. RESULTS: IS6 is the first patient-derived monoclonal IgG antiprothrombin antibody. It bound to prothrombin with low affinity, reacted with 3 phospholipids (cardiolipin, phosphatidylethanolamine, and phosphatidylserine), and showed lupus anticoagulant activity. Moreover, IS6 enhanced the binding of prothrombin to damaged EC and shortened the EC-based plasma coagulation times. CONCLUSION: These findings suggest that IS6 may promote coagulation in areas of damaged EC in the host, and thus contribute to thrombosis in patients with APS.

Interferon-gamma is required for lupus-like disease and lymphoaccumulation in MRL-lpr mice.

Congenic MRL-lpr mice homozygous and heterozygous for the IFN-gamma gene disruption were created to assess the role of this pleotropic cytokine on the lymphoaccumulation and lupus-like disease of Fas-defective mice. Early death was prevented, and glomerulonephritis severely reduced in IFN-gamma-/- mice. Hypergammaglobulinemia was maintained with a switch from IgG2a to IgG1 predominance, but the dramatic decrease in levels of the dominant IgG2a anti-dsDNA autoantibodies was not associated with a compensatory increase in TH2-associated IgG subclasses. Remarkably, early death and glomerulonephritis were also prevented in IFN-gamma+/- mice, although autoantibody levels and glomerular immune deposits were equivalent to IFN-gamma+/+ lpr mice, indicating the importance of additional locally-exerted disease-promoting effects of IFN-gamma. IFN-gamma-/- mice exhibited reduced lymphadenopathy concomitant to a decrease in DN B220(+) T cells. In vivo BrdU labeling showed reduced proliferation of DN B220(+) cells in IFN-gamma-/- vs. IFN-gamma+/+ lpr mice, while enhanced proliferation of all other T cell subsets was unaffected. Macrophages of IFN-gamma-/-lpr mice expressed markedly decreased levels of MHC class I and II molecules compared with controls. Moreover, the heightened expression of MHC class II molecules on proximal tubules of IFN-gamma+/+ lpr mice was significantly reduced in both IFN-gamma-/- and IFN-gamma+/- mice. The data indicate that IFN-gamma hyperproduction is required for lupus development, presumably by increasing MHC expression and autoantigen presentation to otherwise quiescent nontolerant anti-self T cells, and also by promoting local immune and inflammatory processes.

The proliferative in vivo activities of lpr double-negative T cells and the primary role of p59fyn in their activation and expansion.

To characterize the functional status of lpr T cells and determine whether activation is required for DN cell expansion, we performed in vivo labeling experiments in MRL-+/+, MRL-lpr, and p59fyn-/- MRL-lpr (Fyn-/-) mice. Multicolor FACS analysis of T cells from 8-wk-old mice receiving bromodeoxyuridine (BrdUrd) for 9 days showed that higher proportions of CD4+ and CD8+ lymph node cells were dividing (BrdUrd(high)) in lpr (15%) than in +/+ mice (3%), and the proportion of cycling cells was even higher in the DN (71%) and CD4+ B220+ (54%) lpr subsets. BrdUrd chase experiments documented that activation and division in most DN cells was initiated subsequent to their precursor CD8+ stage. Lymphadenopathy and other disease manifestations were greatly reduced in Fyn-/- lpr mice concomitant to decreased DN cells (from 77 to 20%). BrdUrd chase experiments showed that the division rate, signified by conversion of DN cells from BrdUrd(high) to BrdUrd(low), was severely reduced in Fyn-/- compared with conventional lpr mice, whereas division of all other T cell subsets (CD4+, CD8+, and CD4+ B220+) was equal in both types of mice. We conclude that 1) DN lpr T cells, rather than being end stage, retain the capacity to be activated and repeatedly divide before reaching an anergic or replicative senescence stage; 2) the CD3 zeta-chain-associated Fyn kinase is important to DN T cell signal transduction; 3) DN cells, as functional intermediates of the CD8+ subset, are highly dependent on Fas participation for apoptosis; and 4) DN cells contribute to the early development of the serologic and histologic features of the MRL-lpr lupus disease.