FIG. 7.

Cofactor activity of surface-bound factor H and FHL-1. C. albicans cells were preincubated in NHS treated with EDTA (NHS-EDTA), factor H (fH), or buffer (control), and after washing factor I and ¹²⁵I-labeled C3b were added. Samples from pellet (lanes 1 to 3) and supernatant (lanes 4 to 8) fractions were separated by SDS-PAGE, and C3b and its cleavage products were visualized by autoradiography. Inactivation of C3b to iC3b is observed by the disappearance of the α′-chain of C3b and appearance of α-chain fragments of 68, 46, and 43 kDa. Lanes 3 and 7 represent control reactions in which cells were incubated in buffer. A positive control (+) in which ¹²⁵I-C3b was incubated in the presence of factors H and I to obtain total cleavage of the α′-chain is shown in lane 7. As a negative control (−) ¹²⁵I-C3b incubated in the absence of factor H and the presence of factor I shows the absence of unspecific protease (lane 8).