IMMUNOMODULATORY EFFECT OF GLUCAN FROM Saccharomyces cerevisiae

THESIS. A. C. Pelizon submitted this dissertation for her Masters in Tropical Diseases at Botucatu School of Medicine, São Paulo State, UNESP, Botucatu, São Paulo, Brazil, 2003.

Advisor: Professor Alexandrina Sartori

ABSTRACT. b-glucan has been described as a potent immunomodulatory substance. This study investigated b-glucan effect on the following immunological parameters: macrophage fungicidal activity, natural killer cell (NK) activity, cytokine production, and lymphoproliferation. To evaluate the fungicidal activity, peritoneal adherent cells were infected with viable Paracoccidioides brasiliensis (Pb). The fungicidal effect was quantified 7 days later by the number of colonies developing from the adherent cell lysate. NK activity was tested using ⁵¹Cr-labeled YAC tumor cells. Cytokine production was quantified by ELISA in supernatants from cell cultures stimulated with (Pb), S. aureus, and Concavalin A (ConA). Supernatants were collected after 24 hours for TNF-a and IL-12p40 or 48-hour incubation for IFN-g. The lymphoproliferative response was evaluated by stimulating splenic cells with ConA. b-glucan suspension used in this study was extracted from S. cerevisiae cell walls. All in vivo and in vitro studies were performed using female C57BL/6 mouse cells. For the in vivo studies, the animals received 20 or 100 mg of glucan by IP route 24 or 48 hours before the experiment. For the in vitro investigation, 20 or 100 mg of glucan were added directly to cell cultures from normal (non-treated) animals. In vivo glucan treatment triggered a differential immunomodulatory activity, depending on the parameter being evaluated. In this case, b-glucan increased the fungicidal activity, IL-12p40 and TNF-a production, and also NK activity. This treatment, however, inhibited IFN-g production and T cell proliferation in response to ConA stimulation. Similarly to in vivo effects, the in vitro glucan addition increased IL-12p40 and TNF-a production and inhibited IFN-g production and splenic cell proliferation. The fungicidal and NK activities evaluated in vitro were not affected by glucan. We believe these results are important not only because they confirm some effects already described in literature, but also because they show some glucan activities that have not yet been demonstrated. In addition, this study emphasizes the complexity associated with glucan immunomodulatory effect.

KEY WORDS: glucan, Saccharomyces cerevisiae, immunomodulation, IL-12, TNF-a, IFN-g, NK cells.

CORRESPONDENCE TO: Ana Cláudia Pelizon. Departamento de Microbiologia e Imunologia, Instituto de Biociências, UNESP, 18618-000, Botucatu, São Paulo, Brasil. E-mail: acpelizon@bol.com.br