Neurocysticercosis (NCC) is a common central nervous system (CNS) infection caused by Taenia solium metacestodes. Despite the well-documented importance of the granulomatous response in the pathogenesis of this infection, there is limited information about the types of cells and cytokines involved. In fact, there has been limited characterization of human brain granulomas with any infectious agent. In the present study a detailed histological and immunohistochemical analysis of the immune response was performed on eight craniotomy specimens where a granuloma surrounded each T. solium metacestode. The results indicated that in all the specimens there was a dying parasite surrounded by a mature granuloma with associated fibrosis, angiogenesis, and an inflammatory infiltrate. The most abundant cell types were plasma cells, B and T lymphocytes, macrophages, and mast cells. Th1 cytokines were prevalent and included gamma interferon, interleukin-18 (IL-18), and the immunosuppressive, fibrosis-promoting cytokine transforming growth factor ␤. The Th2 cytokines IL-4, IL-13, and IL-10 were also present. These observations indicate that a chronic immune response is elicited in the CNS environment with multiple cell types that together secrete inflammatory and anti-inflammatory cytokines. In addition, both collagen type I and type III deposits were evident and could contribute to irreversible nervous tissue damage in NCC patients.

Patients with paracoccidioidomycosis often present pulmonary fibrosis and exhibit important respiratory limitations. Based on an already established animal model, the contribution of viable and non-viable P. brasiliensis propagules to the development of fibrosis was investigated. BALB/c male mice, 4-6 weeks old were inoculated intranasally either with 4x10(6) viable conidia (Group I), or 6. 5x10(6) fragmented yeast cells (Group II). Control animals received PBS. Six mice per period were sacrificed at 24, 48, 72h (initial) and 1, 2, 4, 8, 12 and 16 weeks post-challenge (late). Paraffin embedded lungs were sectioned and stained with H&E, trichromic (Masson), reticulin and Grocot&tacute;s. During the initial period PMNs influx was important in both groups and acute inflammation involving 34% to 45% of the lungs was noticed. Later on, mononuclear cells predominated. In group I, the inflammation progressed and granulomas were formed and by the 12th week they fussed and became loose. Thick collagen I fibers were observed in 66.6% and 83.3% of the animals at 8 and 12 weeks, respectively. Collagen III, thick fibers became apparent in some animals at 4 weeks and by 12 weeks, 83% of them exhibited alterations in the organization and thickness of these elements. In group II mice, this pattern was different with stepwise decrease in the number of inflammatory foci and lack of granulomas. Although initially most animals in this group had minor alterations in thin collagen I fibers, they disappeared by the 4th week. Results indicate that tissue response to fragmented yeast cells was transitory while viable conidia evoked a progressive inflammatory reaction leading to granuloma formation and to excess production and/or disarrangement of collagens I and III; the latter led to fibrosis.

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