Activation of human complement system Paracoccidioides brasiliensis and its deposition on the yeast form cell surface

The yeast form of Paracoccidioides brasiliensis strain Pb18 was able to activate C3 of normal human serum diluted in phosphate-buffered saline or EGTA-MgCl2 in vitro. C3 convertase was also permissive when Pb18 cells were pre-treated with a pool of immune serum from patients with paracoccidioidomycosis and incubated in serum diluted in EDTA-CaCl2. The components C3, and fragments C3c, C3d, C3g, factor H, factor B, C4 and C5b-9 were demonstrated on the Pb18 cell surface by immunofluorescence although no effect was seen on fungal viability.