A novel murine model of late-phase reaction of immediate hypersensitivity

We describe here a novel experimental model of late-phase reaction of immediate hypersensitivity developed in mice. It consists of introducing small fragments of heat-coagulated hen egg white into the subcutaneous tissue of mice. After 14 days, animals challenged with purified ovalbumin into the footpad presented an immediate swelling of the paw peaking at 30 min, followed by two peaks of swelling at 6 and 24 h. Histological examination of the paws showed a massive eosinophil infiltration (more than 800 cells/5 microscopic fields). This intense infiltration persisted for more than 14 days after the challenge. Furthermore, in mice immunized with coagulated egg white the delayed swelling of the paws and eosinophilic infiltration were significantly higher than in mice immunized with the classical protocol of ovalbumin in alumen adjuvant. Transfer of lymph node cells obtained from mice implanted with heat-coagulated hen egg white induced footpad swelling and eosinophil infiltration in response to ovalbumin. High levels of ovalbuminspecific IgG1 but not of IgE were detected in the serum of these animals. The advantages of this model for the experimental study of late-phase reaction per se and its relevance to the study of allergic diseases such as asthma are discussed.     

Characterization of an 84 kDa protein inducing an immediate hypersensitivity reaction in rabbits sensitized to Haemaphysalis longicornis ticks

An immunogenic 84 kDa protein was isolated and purified from whole tick extracts of Haemaphysalis longicornis larvae by a combination of ion exchange, reverse phase and hydrophobic interaction chromatographies. The protein, when injected intradermally into rabbits exposed to repeated tick feeding, induces an immediate cutaneous hypersensitivity reaction. It has been purified to homogeneity as shown by sodium dodecyl sulphate polyacrylamide gel electrophoresis and silver staining. Amino acid sequences for two peptides derived from proteolytic cleavage of p84 were scanned against known proteins on the SWISS-PROT database. A 7 residue motif, ISGWGNT present in one of the two peptides appeared conserved in both vertebrate and invertebrate trypsin-like serine proteinases, while another 7 amino acid motif, HVPAGQI present in the second peptide showed homology to an Escherichia coli ATP-binding protein. We have discussed our findings in relation to isolation and characterization of target antigens for tick vaccine candidates.     

Contribution of Langerhans cell-derived IL-18 to contact hypersensitivity

The epidermal Langerhans cells (LC), a member of the dendritic cell family, and the LC-derived cytokine IL-12 play a pivotal role in the initiation of contact hypersensitivity (CHS), a Th1 immune response in the skin. Because IL-18, another LC-derived cytokine, shares functional and biological properties with IL-12, we examined a potential role for IL-18 in CHS initiation. Our studies demonstrated that during the induction phase of murine CHS, IL-18 mRNA was significantly up-regulated in the skin-draining lymph nodes (LN). Migratory hapten-modified LC in LN expressed high levels of IL-18 mRNA and secreted functional IL-18 protein. LN cells produced significant amounts of IFN-gamma following in vitro IL-12 stimulation, which could be partially blocked by anti-IL-18 Ab, suggesting a synergistic role for endogenous IL-18 in IFN-gamma production by LN cells. Because mature IL-18 requires cleavage of immature precursors by caspase-1, we further examined IL-12-induced IFN-gamma production in caspase-1(-/-) LN cells. An impaired IFN-gamma production was seen in caspase-1(-/-) LN cells, which could be restored by addition of exogenous IL-18, supporting a role for caspase-1-cleaved, mature IL-18 in IFN-gamma production. Finally, in vivo studies showed that CHS responses were significantly inhibited in mice treated with neutralizing IL-18 Ab as well as in caspase-1(-/-) mice deficient in mature IL-18, indicating functional relevance for IL-18 in CHS. Taken together, our studies demonstrate that LC-derived IL-18 significantly contributes to CHS initiation.     

Contribution of macrophages to peripheral neuropathic pain pathogenesis

Neuropathic pain pathogenesis is not only confined to changes in the activity of neuronal systems, but also involves neuro-immune interactions mediated by inflammatory cytokines and chemokines. Among the immune cells involved in these interactions, macrophages and their central nervous system counterparts – microglia – are actively involved in the generation of peripheral neuropathic pain. Depending on the type of lesion (traumatic, metabolic, neurotoxic, infections or tumor invasion), the profile of the activated macrophages and microglia in terms of time, place and subtype can substantially vary, due to their remarkable plasticity that allows tuning their physiology according to microenvironmental signals. Knowing what and when specific macrophages activate after a peripheral nerve lesion could help in creating a pattern that can be further used to target the macrophages with cell-specific therapeutics and remit chronicization and complications of neuropathic pain. This minireview summarizes recent findings on the specific contribution of macrophages in different neuropathic pain models.     

Schistosoma mansoni: immediate hypersensitivity to adult antigens in the rat

Antigen fractions from adult S. mansoni, obtained from infected mice, were isolated by a variety of methods. A readily soluble fraction was obtained in good yield by freezing and thawing the schistosomes, while the less soluble residue was fractionated by the use of a number of the methods currently used for the extraction of tissue and cell surface antigens. The dialyzed, centrifuged products were characterized by acrylamide gel disc electrophoresis methods, agar gel precipitin reactions with antisera from rabbits immunized with whole schistosome homogenate, and by Prausnitz-Kustner (P-K) assay with sera from schistosome infected rats. The pattern of P-K reactivity suggested that there were a number of different antigen specificities involved in the reaginic antibody response to schistosome infection in rats. With repeated infection and increased duration of infection, more different antigens seemed to be involved in the reagin response. The schistosome antigen fraction obtained by freezing and thawing was especially reactive with both early infection rat sera and sera from multiply infected rats. Both the soluble fraction isolated by freezing and thawing and residue solubilized materials were found to be able to induce the formation of reagin antibodies on immunization with alum and B. pertussis vaccine.     

The specificity of delayed hypersensitivity to ABA-tyr-pulsed and ABA-coupled macrophages

Guinea pigs immunized with ABA-tyr in CFA respond well by skin test to ABA-tyr-pulsed macrophages but poorly to ABA-coupled macrophages and not at all to ABA-coupled red cells, thymocytes, or L₂C cells. On the other hand, guinea pigs immunized with ABA-coupled macrophages do not respond to ABA-insulin or ABA-tyr-pulsed macrophages but do respond to ABA-coupled macrophages. Similarly guinea pigs immunized with Ars-NCS-coupled macrophages respond only to the homologous antigen. The specificity of these reactions is determined by how ABA is associated with the Ia-positive accessory cell. The presence of Ia molecule is not a sufficient condition since neither Ia-positive L₂C cells nor spleen cells depleted of adherent macrophages are effective as immunogens or elicitors of response when coupled with ABA. These results suggest that the topography of the ABA and Ia complex formed on the accessory cell is the prime determinant of specificity for T-cells responses.     

Delayed hypersensitivity reaction to rat xenoantigens in mice

A scheme of delayed-type hypersensitivity (DTH) to xenogeneic lymphoid cells induced in mice was suggested. Subcutaneous injection of normal mice with 5 X 10(6) rat spleen cells in a complete Freund's adjuvant with the results evaluated 5 days after was found the optimal condition for DTH development. Mediated by T lymphocytes the response was shown to be maximal 24 hours after the challenge.     

Transfer of delayed hypersensitivity to leishmanin (Montenegro reaction).

It was possible to transfer the cutaneous leishmanin hypersensitivity (Montenegro reaction) to 7 out of 12 recipients. The diameter of the indurations observed ranged from 8 to 25 mm. Histological examination of skin biopsies from the site of three positive Montenegro reactions showed intense mononuclear infiltrate of lymphocytes and histiocytes, and one biopsy showed the feature of tuberculoid granuloma. Four recipients retested with leishmanin after 11, 22, 25, and 32 days, still showed positive reactions.     

The characterization of the delayed-type hypersensitivity reaction to H-Y antigens

We have evaluated the ability of certain inbred strains of mice to develop a delayed-type hypersensitivity response to the male H-Y antigen. It was found that C57BL/10, B10.GD and B10.A(5R) female mice responded to syngeneic male cells. B10.A(4R) females also responded to B10.A(4R) male cells although the reactivity was somewhat slighter. B10.A(2R), B10.D2 and BALB/c female mice could not respond to immunization with syngeneic male cells. The response was male-antigen specific and transferable by thymus-derived cells. Moreover, suggestive evidence of representation of H-Y was obtained, based on the ability of responder strains immunized with syngeneic cells to react to nonresponder male cells upon challenge.     

Contribution of the complement system to antibody-mediated binding of Trypanosoma gambiense to macrophages

The role of complement in the process of binding of trypanosomes to macrophages in the presence of specific antibody was studied. The aggregation of trypanosomes observed at the optimal antigen-antibody ratio or in the presence of excess antigen inhibited the binding. Complement caused clumped trypanosomes to dissociate, and the free trypanosomes, which were presumed to be coated with antibody that had fixed complement, readily attached to surfaces of phagocytes. Thus, complement was shown to contribute at the site of the antigen-antibody reaction to the creation of an environment suitable for the binding. It seems likely that the trypanosomes dissociated by complement adhered to C3 receptors of the macrophage. However, in the absence of complement and in regions of antibody excess, free trypanosomes also attached to phagocytes. Thus phagocytes may also have receptors for the Fc portion of aggregated antibody. Complement activated by the alternate pathway also enhanced attachment of trypanosomes to phagocytes, but the effect was not as rapid as it was when complement was activated by classical means.     

Spinal macrophages resolve nociceptive hypersensitivity after peripheral injury

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Amblyomma cajennense ticks induce immediate hypersensitivity in horses and donkeys

Since host immune reaction to ticks interferes with tick-borne pathogen transmission, it is important to recognize naturally occurring tick-host immune relationships to better understand the epidemiology of such infectious diseases. Amblyomma cajennense is an important tick-borne disease vector in the Neotropical region and horses maintain it in domestic environments. In the present work intradermal testing of A. cajennense tick exposed horses and donkeys using crude tick antigens was used to evaluate the type of hypersensitivity induced by infestations. Animals sensitized by A. cajennense infestation displayed an immediate hypersensitivity reaction at the antigen inoculation site. Foals sensitized with experimental infestations and field sensitized horses presented the most intense reactions (40% of ear thickness increase). Field sensitized donkeys presented less intense reaction reaching no more than 22% of mean thickness increase. Control horses (non-sensitized) had the least intense reaction, with a peak of no more than 12% of increase. The presence of a prominent immediate hypersensitivity in equids sensitized experimentally or by field infestations indicates that A. cajennense ticks induce in this host an immune response that is associated with IgE production and which is known to be inappropriate against intracellular pathogens. Differences observed between horses and donkeys are discussed.     

Mast cell-independent mechanisms of immediate hypersensitivity: a role for platelets

Mast cells have been implicated as the central effectors in allergic responses, yet a fatal anaphylactic response can be induced in mast cell-deficient mice. In this study, we examined the immediate hypersensitivity response in wild-type (WT) and mast cell-deficient mice (W/W(v)) in two different tissues (skin and skeletal muscle). Vascular permeability and leukocyte recruitment were studied after immediate challenge or 4 h postchallenge in OVA-sensitized mice. In skin, immediate challenge induced a significant increase in vascular permeability (75%) within 30 min and was accompanied by increased leukocyte adhesion 4 h postchallenge. In the absence of mast cells, no changes in vascular permeability or leukocyte recruitment were observed in skin. In WT skeletal muscle, immediate challenge induced a rapid increase (80%) in vascular permeability within 5 min and significant leukocyte recruitment after 4 h. Surprisingly, in W/W(v), a gradual increase in vascular permeability was observed, reaching a maximum (50%) within 30 min. Despite the absence of mast cells, subsequent leukocyte emigration was similar to that observed in WT mice. Pretreatment with anti-platelet serum in W/W(v) returned Ag-induced vascular permeability and leukocyte recruitment to baseline. Platelets were shown to interact with endothelium in skeletal muscle, but not dermal microvasculature. These data illustrate that mast cells play a prominent role in vascular permeability and leukocyte recruitment in skin in response to Ag, however, in skeletal muscle; these changes can occur in the absence of mast cells, and are mediated, in part, by the presence of platelets.     

Decentralization of the superior cervical ganglia and the immediate hypersensitivity response.

Bilateral decentralization of the superior cervical ganglia protects against pulmonary inflammation when measured 8 hr after induction of anaphylaxis in rats sensitized to the nematode, Nippostrongylus brasiliensis. Since anaphylactic shock produces immediate perturbations to the cardiovascular and respiratory systems, we examined whether bilateral decentralization of the superior cervical ganglia modified the responses of these two systems during the first 4 hr of the anaphylactic response. With the exception of the bronchioles, decentralization did not protect against anaphylaxis-associated increases in extravasation of albumin, and the small changes in respiratory function induced by anaphylaxis were unaffected by the denervation. Decentralization did not alter anaphylaxis-induced reductions in blood flow to the gastrointestinal tract; however, blood flow to the kidneys and spleen of decentralized rats was restored more rapidly to normal values. These results suggest that the protective effect of decentralization on the late phase pulmonary inflammation of anaphylaxis is unrelated to early changes in respiratory mechanics, although the protection may be facilitated by the more rapid re-establishment of normal cardiovascular homeostasis.