Immunopathology of Coccidioidal Granulomata and the Regulation of Interleukin-12 Signal Transduction in Human Coccidioidomycosis
Committee ChairAmpel, Neil M.
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PublisherThe University of Arizona.
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AbstractCoccidioidomycosis is a growing problem in the United States. There is still an incomplete understanding of the immunological response associated with human coccidioido-mycosis, although previous studies have indicated that cell-mediated immunity (CMI) is critical in the control of this disease. We have examined necrotizing pulmonary coccidioidal granulomata using immunohistochemical staining for lymphocyte subsets and for the cytokines interleukin-10 (IL-10) and gamma interferon (IFN-?). Discrete perigranulomatous lymphocytic clusters were identified containing roughly equal numbers of T (CD3+) and B (CD20+) lymphocytes. While the number of cells expressing IL-10 was similar in the mantle and in the perigranulomatous clusters, there were significantly more cells expressing IFN-? in the mantle compared to the clusters (P = 0.037). Confocal microscopy revealed that CD4+ T lymphocytes and B lymphocytes are associated with IL-10 production. CD4+CD25+ T lymphocytes were also identified in the perigranulomatous clusters but were not associated with IL-10 production. This is the first report noting perigranulomatous lymphocyte clusters and IL-10 in association with human coccidioidal granulomata, suggesting a down-regulation of cellular immune response.IL-12 is critical in driving a T helper type 1 (Th1) immune response. To understand the mechanism associated with hyporesponsiveness to IL-12 stimulation seen in some anergic patients with disseminated coccidioidomycosis, IL-12 receptor expression and function were determined in PBMCs from immune and nonimmune healthy donors. By using a relative quantitative RT-PCR technique, we found that IL-12R?1 is constitutively expressed in PBMCs and is equally up-regulated by coccidioidal antigen preparation T27K in both immune and nonimmune donors. On the other hand, the IL-12R?2 expression level is increased by T27K only in PBMCs from immune but not nonimmune donors. In addition, the increased IL-12R?2 expression in immune PBMCs is correlated with Stat4 activation and the induction of IFN-? production by IL-12. These data suggest that the IL-12R?2 expression and signal transduction is functional in host immunity against Coccidioides infection. Subsequent research, which involved the stimulation of lymphocytes with autologous dendritic cells (DCs) pulsed with T27K, revealed that the up-regulation of IL-12R?2 expression and signal transduction is associated with the induction of IFN-? production by DCs pulsed with T27K.
Degree ProgramMicrobiology & Immunology