Cooperative activation of TLR2 and bradykinin B2 receptor is required for induction of type 1 immunity in a mouse model of subcutaneous infection by Trypanosoma cruzi.

We have previously reported that exogenous bradykinin activates immature dendritic cells (DCs) via the bradykinin B(2) receptor (B(2)R), thereby stimulating adaptive immunity. In this study, we show that these premises are met in a model of s.c. infection by Trypanosoma cruzi, a protozoan that liberates kinins from kininogens through its major protease, cruzipain. Intensity of B(2)R-dependent paw edema evoked by trypomastigotes correlated with levels of IL-12 produced by CD11c(+) dendritic cells isolated from draining lymph nodes. The IL-12 response induced by endogenously released kinins was vigorously increased in infected mice pretreated with inhibitors of angiotensin converting enzyme (ACE), a kinin-degrading metallopeptidase. Furthermore, these innate stimulatory effects were linked to B(2)R-dependent up-regulation of IFN-gamma production by Ag-specific T cells. Strikingly, the trypomastigotes failed to up-regulate type 1 immunity in TLR2(-/-) mice, irrespective of ACE inhibitor treatment. Analysis of the dynamics of inflammation revealed that TLR2 triggering by glycosylphosphatidylinositol-anchored mucins induces plasma extravasation, thereby favoring peripheral accumulation of kininogens in sites of infection. Further downstream, the parasites generate high levels of innate kinin signals in peripheral tissues through the activity of cruzipain. The demonstration that the deficient type 1 immune responses of TLR2(-/-) mice are rescued upon s.c. injection of exogenous kininogens, along with trypomastigotes, supports the notion that generation of kinin "danger" signals is intensified through cooperative activation of TLR2 and B(2)R. In summary, we have described a s.c. infection model where type 1 immunity is vigorously up-regulated by bradykinin, an innate signal whose levels in peripheral tissues are controlled by an intricate interplay of TLR2, B(2)R, and ACE.

The interaction of alpha 1-proteinase inhibitor and tissue kallikrein in controlling allergic ovine airway hyperresponsiveness.

We reported previously that the development of airway hyperresponsiveness (AHR) 24 h after antigen challenge in allergic sheep was associated with increased tissue kallikrein activity (TK) and decreased alpha-1-proteinase inhibitor (alpha 1-PI) activity in bronchoalveolar fluid (BAL). The inverse correlation between TK and alpha 1-PI in these experiments suggested that administration of alpha 1-PI might reduce TK activity and block AHR. To test this hypothesis, airway responsiveness, as determined by calculating the cumulative carbachol breath units (BU) that increased specific lung resistance by 400% (PC400), was measured before and 24 h after aerosol challenge with Ascaris suum antigen in seven sheep hypersensitive to this antigen. On the next day, 30 min before the 24 h PC400 measurement, the sheep were treated with either aerosol alpha 1-PI (Prolastin, 10 mg/5 ml) or denatured (DN) prolastin (10 mg/5 ml), which had only 10% of its original activity. BAL was also performed before and 24 h after challenge for the measurement of TK and alpha 1-PI activity. Treatment with DN-Prolastin at 24 h after antigen challenge did not block antigen-induced AHR: PC400 fell from a baseline (mean +/- SE) of 26.0 +/- 3.2 BU to 11.2 +/- 1.5 BU after challenge (p < 0.05). This AHR was associated with increased TK (363%, p < 0.05) and decreased alpha 1-PI activity (65%, p < 0.05). Prolastin treatment at 24 h blocked the AHR: PC400 was 21.0 +/- 2.8 before and 23.2 +/- 3.7 after challenge (p < 0.05 versus DN-Prolastin) and the changes in BAL TK (28% increase) and alpha 1-PI activities (15% increase) were not different from baseline (both p < 0.05 versus DN-Prolastin). There was a significant inverse correlation between alpha 1-PI activity and TK activity in BAL, as well as the changes between baseline and 24 h in alpha 1-PI activity and TK activity in BAL Pretreatment (30 min before antigen challenge) with Prolastin also protected against the antigen-induced AHR. The effect of Prolastin was also seen against aerosol challenge with high-molecular-weight kininogen (HMWK), a substrate of TK. HMWK caused bronchoconstriction which was blocked by Prolastin (p < 0.05), and the bradykinin B2 antagonist, NPC-567 (indicating that kinins were generated), but not DN-Prolastin or the elastase inhibitor, ICI 200, 355. Although the negative association between alpha 1-PI activity and TK activity identified in this study does not prove cause and effect, our findings do raise the possibility that in vivo alpha 1-PI may regulate TK activity and allergen-induced AHR.

Flaujeac factor deficiency. Reconstitution with highly purified bovine high molecular weight-kininogen and delineation of a new permeability-enhancing peptide released by plasma kallikrein from bovine high molecular weight-kininogen.

Flaujeac trait is the functional deficiency of a plasma protein of the intrinsic coagulation, kinin-forming, and plasma fibrinolytic pathways. The Flaujeac factor in man has been isolated and tentatively identified as a kininogen of high molecular weight (HMW). Highly purified bovine HMW-kininogen, but not bovine low molecular weight kininogen, repaired Flaujeac factor deficiency. The two subspecies of this molecule, HMW-kininogen a and HMW-kininogen b, also corrected Flaujeac factor deficiency. When bovine HMW-kininogen was incubated with bovine plasma kallikrein, kinin-free HMW-kininogen, bradykinin, and a glycopeptide fragment (peptide 1-2; 12,584 daltons) were rapidly released. None of these fragmentation products corrected Flaujeac factor deficiency alone or in mixtures. The function of HMW-kininogen appeared to depend upon the structural integrity of the native molecule. When injected in concentrations of 2 pmol-8 nmol/0.1 ml, peptide 1-2 caused increased vascular permeability in rabbits, rats, or guinea pigs. The enhanced permeability was maximal within 1-2 min and terminated in 5-10 min, differing from that of bradykinin or histamine. Injected together in equimolar amounts, peptide 1-2 and bradykinin produced a synergistic permeability response which was immediate in onset as well as prolonged in duration. Peptide 1-2 is a rapidly acting, highly basic glyco-peptide which mediates increased vascular permeability in a complementary and synergistic manner with bradykinin.