In this disease, CD4+ T cells, B cells and macrophages infiltrate the synovium, where they are activated and contribute to local destruction. bristles causes symptoms of acute inflammation. A chronic inflammatory reaction frequently occurs in individuals after multiple contacts, and this reaction is characterised by articular synovial membrane thickening ABT-492 (Delafloxacin) with joint deformities, common characteristics of chronic synovitis. Extract from the bristles has been shown to induce an intense inflammatory response in a murine model, and this reaction was characterised by the presence of neutrophils in the paw tissues of injected mice and a strong, specific antibody response. There is not yet an effective treatment for incidents involving contact with pararama. In this study, we evaluated the phenotype of the immunological response and cytokine production in BALB/c mice subcutaneously injected in the footpad with bristle extract or sterile saline (control) seven times at 15 day intervals. An analysis of cells from the draining lymph node by flow cytometry showed that the absolute numbers of TCD4, TCD8 and B lymphocytes, as well as the expression of activation molecules, were higher in the extract-treated group. Furthermore, immunohistochemistry and immunofluorescence analyses showed a mixed inflammatory infiltrate composed of neutrophils and macrophages at the inoculation site. In addition, ABT-492 (Delafloxacin) an analysis of paw cytokines showed elevated levels of IL-6, IL-12, IL-10, IL-17 and IL-23 after the 7th inoculation. In conclusion, these data provide evidence of pro-inflammatory changes in the phenotypes of immune cells and cytokine production in animals subjected to injections with an extract from bristles, which may explain the intense and prolonged inflammatory response that characterises this disorder. Introduction The Brazilian moth (Walker, 1856), usually called pararama in its larval stage, belongs to the Arctiidae family and inhabits rubber plantations in the Amazon region, feeding of the rubber tree shares many features with the symptoms of inflammatory joint disease, unlike the clinical manifestations presented by the venom of other caterpillars, such as the erythema, kidney and liver damage caused by sp. (Saturniidae) , ; allergic reactions induced by contact with (Lymantriidae) ; and homeostatic ABT-492 (Delafloxacin) abnormalities such as blood coagulation and fibrinolysis, as well as bleeding through the mucous membranes and internal organs including the brain (which may lead to death), caused by contact with sp. (Saturniidae) , . The most common form of the inflammatory joint disease is Hhex rheumatoid arthritis (RA), a chronic, systemic disorder that causes inflammation in the synovium , . In this disease, CD4+ T cells, B cells and macrophages infiltrate the synovium, where they are activated and contribute to local destruction. Additionally, neutrophils accumulate in the synovial fluid, where they engulf immune complexes and release proteolytic enzymes. Furthermore, a broad array of macrophage and fibroblast cytokines, including interleukin (IL)-1, IL-6, IL-15, IL-18, tumour-necrosis factor (TNF)-, granulocyte-macrophage colony-stimulating factor (GM-CSF), various chemokines, and many others, are produced by the rheumatoid synovium. These ABT-492 (Delafloxacin) cytokines, as well as proteases that contribute to cartilage destruction, perpetuate the inflammation . Small but physiologically relevant amounts of IFN- and IL-17 cytokines are expressed in RA, which may contribute to immune responses, fibroblast activation and bone destruction . Despite its similarity with some inflammatory joint features, the disease caused by contact with does not seem to be a systemic autoimmune disorder because it does not induce the generation of autoantibodies, such as anti-DNA or anti-collagen type II, as shown in our previous ABT-492 (Delafloxacin) study. Moreover, we have demonstrated that caterpillar bristles’ crude extract presents strong proteolytic activity. We observed that the bristles’ extract can induce an intense inflammatory process, characterised by the presence of neutrophils in the paw tissues of injected mice and a strong, specific antibody response . To better understand the participation of the elements of the immune system in the development of the disease induced by the caterpillar, this study aimed to evaluate the phenotype of the immunological response induced by repeated injections of the caterpillar bristle extract in a murine model. Materials and Methods Extract of Caterpillar Bristles Caterpillars from were collected in non-protected areas of the city of S?o Francisco do Par, Par, Brazil (license for capture, transportation and maintenance of the animals were provided by Chico Mendes Institute for Biodiversity Conservation (ICMBIO) of the Brazilian Ministry of the Environment C permission no. 11971C2) and maintained at the Immunochemistry Laboratory, Butantan Institute, SP, Brazil. The bristle extract was prepared after incubating the caterpillars at 4C for a few minutes; the bristles were cut off with scissors at the point of insertion in the tegument, avoiding any tegument incision, and then suspended in cold phosphate-buffered saline (PBS) (8.1 mM sodium phosphate, 1.5 mM potassium phosphate, 137 mM sodium chloride.