The Paracoccidioides brasiliensis gp70 antigen is encoded by a putative member of the flavoproteins monooxygenase family.

Glycoprotein gp70 is an important intracellular antigen from Paracoccidioides brasiliensis that elicits both humoral and cellular immune responses. Herein, the PbGP70 gene cloning from isolate Pb18 using internal peptide sequence information is reported. The deduced protein sequence bears two N-glycosylation sites, antigenic sites and two mouse T-cell epitopes. Anti-recombinant gp70 (rPbgp70) polyclonal antibodies reacted with a 70-kDa component in total cell extract of P. brasiliensis, while MAbC5F11 and paracoccidioidomycosis patients' sera recognized rPbgp70. Confocal microscopy with anti-rPbgp70 and MAbC5F11 showed intense staining and cytoplasmatic co-localization. The protein sequence belongs to the flavoprotein monooxygenase family which groups important anti-oxidative bioactive compounds. We found increased PbGP70 transcript accumulation under oxidative stress induced by H(2)O(2), during fungal growth and in macrophage phagocyted/bound yeasts. Therefore, gp70 might play a dual role in P. brasiliensis by both eliciting immune cellular and humoral responses in the host and protecting the fungus from oxidative stress generated by phagocytic cells.

[Pharmacologically immunosuppressed mice as a model for study of opportunistic parasite infections]. / Camundongos imunossuprimidos farmacologiamente como modelo para estudo de infecções parasitárias oportunistas.

Immunodeficient animals are important research models for studies in parasitology, oncology and immunology. Immunosuppressive drugs have been experimentally used to obtain a state of immunodeficiency in mice. This investigation aimed to quantify the circulating T and B cells of mice treated with the immunosuppressive agents dexamethasone (Dx), cyclosporine (CsA) and cyclophosphamide (CY), as well as to observe the behaviour of lymphocytic populations in the spleen of these animals. Blood samples were collected for counting the total peripheral blood leukocytes and T and B lymphocytes using flow cytometry. Total leukocytes of mice treated with the three drugs during all study showed a significant decrease when compared to the results of the control group. The proportion of B and T lymphocytes from the treated animals also decreased significantly. Spleen sections revealed a moderate decrease in the cellularity of the white pulp and the development of lymphocyte apoptosis in mice from groups treated with CY and Dx. Results showed that the proposed experimental models demonstrated to be suitable for studies of murine immunodeficiency.

Tolerogenic property of B-1b cells in a model of allergic reaction.

Since B-1 cells were first described, their origin and function remain controversial. Given the ability to produce natural antibodies and large amounts of IL-10, there is a consensus about their role in innate immunity. More recently, however, B-1 cells have been associated to adaptive immunity as well, due to the demonstration of immunological memory and antigen presentation capability. Here we demonstrate that adoptive transfer of pre-sensitized B-1b cells (obtained from OVA-sensitized mice) to naïve B-1 deficient animals, drastically affects the ability of transplanted animals to mount an adaptive response upon immunization with OVA. In contrast to naïve B-1 populated mice, mice transplanted with sensitized B-1 exhibit lower anti-OVA antibody levels, milder footpad swelling in response to OVA subcutaneous injection and reduced granulomatous reaction to OVA-coated beads. Moreover, we show that these pre-sensitized B-1 cells, when acting as APCs, induce poor T cell proliferation in vitro when compared with macrophages or B-1 cells obtained from naïve mice. This property may be due in part to insufficient expression of the co-stimulatory molecule CD86, necessary for optimal antigen presentation. In conclusion, our data suggest a novel role for B-1 cells as part of suppressor mechanisms in the immune system.