IN VITRO AND IN SITU ACTIVATION OF THE COMPLEMENT SYSTEM BY THE FUNGUS Lacazia loboi

VILANI-MORENO F. R.(1), MOZER E.(1), SENE A. M. G.(1), FERASÇOLI M. O.(1), PEREIRA T. C.(1), SOUZA G. H. P.(1), MIRAS M. R. G.(1), BELONE A. F. F.(1)

(1)Equipe Técnica de Biologia & Equipe Técnica de Patologia,  Instituto Lauro de Souza Lima, Bauru, SP, Brazil.

Since activation of the complement system (CS) by fungal cells represents an important defense mechanism of the host, and since so far no study exists evaluating the participation of the CS in Jorge Lobo’s disease and its activity on the fungus Lacazia loboi, the etiological agent of this mycosis, we carried out the present study.L. loboi was obtained from the footpads of BALB/c mice inoculated 10 months earlier. The viability index of the fungus was 48%. Fungal suspensions (2 x 106 cells) were incubated at 37ºC with a pool of inactivated serum from patients with the mycosis or with sterile saline for 30 min. Next, the tubes were incubated for 2 h with a pool of noninactivated AB+ serum (as a complement source), serum diluted in EGTA-MgCl2 (to block the classical route of CS activation), serum diluted in EDTA (to block the two routes of CS activation), and inactivated serum. After centrifugation, fungal cells were resuspended in 0.5 ml sterile saline. The viability index of L. loboi was evaluated by staining with fluorescein diacetate/ethidium bromide and the remaining suspension was cytocentrifuged. The slides were submitted to immunofluorescence staining using fluorescein isothiocyanate-conjugated human anti-C3 monoclonal antibody. The results revealed that 96% of the fungi activated the CS by the alternative route and no significant difference in L. loboi viability was observed after CS activation. In parallel, frozen histological sections from 11 patients with the mycosis were analyzed regarding the presence of C3 and IgG by immunofluorescence staining. C3 deposits were observed in the fungal wall in 100% of the lesions analyzed and IgG deposits in 91%. The results suggest that the CS is activated in Jorge Lobo’s disease and may contribute to the host’s defense through macrophage-mediated L. loboi opsonization and phagocytosis.

KEY WORDS: complement system, Lacazia loboi, Jorge Lobo’s disease.

CORRESPONDENCE TO:

Fátima Regina Vilani Moreno, Equipe Técnica de Biologia, Instituto Lauro de Souza Lima. Rodovia Comte. João Ribeiro de Barros, Km 225/226, 17034-971, Bauru, SP. Email: fmoreno@ilsl.br