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  • 1
    ISSN: 1573-0832
    Keywords: Cryptococcus neoformans ; macrophages ; T suppressor cells ; phagocytosis ; antigen presentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The influence of lymphocytes on the modulation of macrophage functions in altered immune states induced by Cryptococcus neoformans infection in rats has been investigated. In this report we observed a decrease of ‘in vitro’ phagocytic activity by peritoneal cells (PC) from rats that received T suppressor cells induced by cryptococcal infection, against both the same microorganism that stimulated this suppressor population (p〈0.05) and another non-pathogenic primary yeast (Candida tropicalis), (p〈0.02). The microbicide function of the PC from these animals present a significant decrease in challenge by C. tropicalis (p〈0.002) when compared with PC from animals transferred with T normal cells. The transference of T suppressor cells induced by cryptococcal infection in animals immunized with human serum albumin-complete Freund's adjuvant (HSA-CFA) produces a significant alteration of the phagocytosis to HSA-human red cells (HSA-HRC) when compared with the phagocytosis observed in animals that received T normal cells or the phagocytosis of normal animals (p〈0.001). We could also observe that the DTH to HSA studied during 30 days was negative in rats transferred with PC sensitizated with HSA and treated with suppressor T cells, when compared with the DTH response of animals transferred with PC-HSA cocultured with normal cells (p〈0.05 21st day). The data presented in this paper illustrated that following infection of rats with C. neoformans there is a change in some population of accessory cells behavior reflected by the modification of several functions, such as phagocytosis, lytic activity and antigen presentation.
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  • 2
    ISSN: 1573-0832
    Keywords: Cryptococcus neoformańs ; suppressor cells ; thymus ; thymic index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The presence of the microorganism, cortical hyperplasia and germinal centers was detected in the thymus of rats infected with 107 viable Cryptococcus neoformans cells and immunized at 7 days afterwards with 2.5 mg (0.1 ml) of human serum albumin (HSA) incorporated to complete Freund's adjuvant (CFA) (Group 2). There was no modification of the glandular structure in the thymus of the animals only immunized with HSA-CFA (Group 1). The weight of the thymus of group 2, animals infected and immunized, was increased compared with the weight of the thymus of group 1 animals, this became evident by the increase of the thymic index (TI) (p 〈0.005). This rate was obtained calculating the thymus weight/total body weight ratio × 1000. Thymic cells (107 cells in 1 ml) obtained from both groups of animals were transferred to normal syngeneic rats of the same sex. The recipient rats were immunized with HSA-CFA 24 h later and 14 days after the transference, the response of delayed-type hypersensitivity (DTH) was studied in them. It could be observed that the thymic cells coming from group 2 animals were capable of suppressing significatively the afferent pathway of the DTH response to HSA when compared with the response of the animals that received cells coming from group 1 rats (p〈0.0001).
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  • 3
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The delayed type hypersensitivity response to human serum albumin (HSA) of rats infected intraperitoneally with 107 viable C. neoformans cells, and 7 days after, immunized with human serum albumin was significantly diminished (p〈0.05) when compared with the response observed in rats immunized with human serum albumin and non infected. The spleen mononuclear cells from suppressed rats transferred to normal syngeneic recipients of the same sex suppress the afferent phase of the response (p〈0.02) suggesting that cells present in the spleen might be one of the responsible mechanisms for the suppression to nonrelated antigens in infected animals.
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  • 4
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Rats were infected with Coccidioides immitis and injected with cyclophosphamide three days pre or post infection. Administration of the drug before the infection caused enhancement of DTH response and decrease of the colony forming units (CFU). Conversely, injection of the drug three days post infection produced contrary effects, indicating that a normal T-cell function is essential as a defense mechanism in C. immitis infection.
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  • 5
    ISSN: 1573-0832
    Keywords: Cryptococcus neoformans ; spleen ; efferent T-suppressor cells ; cyclophosphamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using a rat model, we have previously demonstrated that infection with Cryptococcus neoformans can trigger the production of a series of suppressor cells that specifically inhibit the cell-mediated immune response to a non-related antigen, human serum albumin (HSA), that has been injected 7 days after the infection. We previously determined that the cryptococcal infection induces afferent suppressor or suppressor induction cells (Ts1) to HSA. The primary objective of the present study was to investigate the suppressor cells involved in the efferent phase of delayed-type hypersensitivity (DTH) response to HSA in rats infected with C. neoformans and immunized with the non-related antigen and determine the role that the Ts1 cell plays in the induction of that cell. For this purpose, the spleen mononuclear (SpM) cells containing the Ts1 or SpM cells from immunized non-infected rats (used as donor controls) were transferred to two groups of syngeneic naive recipients (first recipients). Later, the SpM cells from both groups of animals were transferred to rats immunized with HSA (second recipients). The efferent limb of the DTH response to HSA was suppressed in the recipients that received SpM cells from donors injected with Ts1 cells. Additional HSA antigen was not required for induction of these efferent suppressor cells. Furthermore, we here show that these cells are resistant to treatment with cyclophosphamide (Cy), and that they can activate another suppressor population. The latter are Cy sensitive and are present in the immune recipient.
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  • 6
    ISSN: 1573-0832
    Keywords: Cryptococcus neoformans ; Indomethacin ; Macrophages ; MHC Class II ; T-suppressor cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract When the I-A and I-E expressions were assessed in peritoneal macrophages fromCryptococcus neoformans infected animals, a significant decrease in the former was observed when compared with normal macrophages (p〈0.001) whereas a significant increase in the I-E expression was observed when compared with controls (p〈0.005). On the other hand, when studying the in vitro action of Ts cells on the macrophages, it was observed that the I-A expression was significantly reduced in macrophages upon contact with Ts cells. Similar results were obtained when Ts cells were replaced by a soluble factor. In contrast, the I-E expression was significantly increased by in vitro action of the Ts cell or its soluble factor. Indomethacin partially restored I-A and I-E expression in the macrophages to control levels.
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  • 7
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study was undertaken to establish the function of T-lymphocytes in protective immunity against a cryptococcal infection in animals treated with Cyclophosphamide (Cy) pre or post infection and to determine how they relate to the progression of the disease. Inbred Suquía rats were infected either intranasally (i.n.) or intraperitoneally (i.p.) with 105 viable Cryptococcus neoformans cells. The infected rats were divided in three groups. One of the groups (group I) was utilized as a control. The second group (group II) was treated with Cy 3 days before the infection. The third group (group III) was treated with Cy 3 days after the infection. At approximately 22 days post infection, C. neoformans growth in selected organs of all animals were determined. In addition, humoral and delayed-type hypersensitivity (DTH) response were assayed in the rats. When the Cy was applied after the infection the DTH was significantly diminished and inverse to the colony forming unit (CFU) which increased leading to the animals death. On the other hand, injection of the drug 3 days before infection did not modify the response, that was comparable in both treated and the control animals. In this study it were found haemagglutinating antibodies in sera from i.n. and i.p. infected rats although at minimal levels and were not present in all animals. The results show that with a low T-cell function induced as a consequence of injecting Cy after the infection, rats did not develop a normal DTH response to cryptococcal infections and were not able to control a cryptococcal infection as well as animals with normal T-cell function.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 82 (1983), S. 179-184 
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A guinea pig model was used to evaluate immune response to Cryptococcus neoformans. This model shared characteristics with cryptococcosis in humans. Twenty five guinea pigs injected intraperitoneally with 107 viable C. neoformans cells developed diseminated disease. Forty days after infection all guinea pigs were killed and autopsy performed. C. neoformans growth in the lungs, brains, livers and spleen of the infected animals were determined. Furthermore, the immune response was characterized by moderate degree of delayed-type hypersensitivity and humoral response. In some organs was observed neutrophyle and lymphocyte infiltration with presence of cryptococci cells. The infiltration observed in the organs was probably a consequence of an immune reaction.
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