EFFECT OF IL-15 ON FUNGICIDAL ACTIVITY AND H2O2 RELEASE BY HUMAN NEUTROPHILS CHALLENGED WITH HIGH VIRULENT STRAIN OF Paracoccidioides brasiliensis

TAVIAN E. G.(1), DIAS-MELÍCIO L. A.(1), BORDON A. P.(1), ACORCI M. J., BIONDO G. A.(1), PERAÇOLI M. T.(1), SOARES A. M. V. C.(1)

(1)Departament of  Microbiology and Immunology, IB, UNESP, Botucatu , SP, Brazil

Phagocytic cells play a critical role against Paracoccidioides brasiliensis. Some  papers have shown the effects of activator  and suppressive cytokines on macrophages and monocytes response to fungus challenge. However the works focusing the involvement  of these mediators on neutrophils antifungal functions are scarcer. Interleukin-15, a key immnoregulatory  cytokine of the innate immune response has been shown to activate certain antimicrobial functions of  neutrophils. Thus, the purpose of this work was to test the effects of IL-15 on fungicidal activity and H2O2 release by human neutrophils challenged with virulent strain of P brasiliensis. Peripheral blood neutrophils obtained from 20 healthy donors were incubated for 18 h with increasing concentrations of IL-15 (6.25, 12.5, 25, 50 and 100 ng/mL) and then challenged with high virulent strain of P brasiliensis (Pb18) by 4 h. After, the cells were evaluated for H2O2 release and fungicidal activity, by counting of colony forming units after plating. No IL-15 incubated cells exhibited a very low fungicidal activity. However, after incubation with this cytokine  a significant increase in neutrophils fungicidal activity was detected. Moreover, H2O2 levels  released by IL-15 incubated cells were higher than those detected for neutrophils alone. Human neutrophils activated with IL-15, increased fungicidal activity against P. brasiliensis  associated with high levels of H2O2.

KEY WORDS: Interleukin 15, P. brasiliensis, human neutrophils.

CORRESPONDENCE TO:

Ângela Maria Victoriano C. Soares, Departamento de Microbiologia e Imunologia do Instituto de Biociências de Botucatu, UNESP, Caixa Postal 510, CEP 18618-000, Botucatu, SP. Email: acsoares@ibb.unesp.br