Activity of native collectin-11 in relation to complement activation. C. albicans were incubated with MBL-defect serum (serumMBL-, 10%) in the absence or presence of mannose (0.1 M) or with MBL-defect serum treated with either mannose-agarose beads or control agarose beads. In addition, we used MBL-defect serum depleted for native collectin-11 (serumMBL-/CL-11-) that was restored with recombinant collectin-11 (rCL-11; 10 µg/ml). C4b (a, d), C3b (b, e) or TCC (c, f) deposition was then determined for both mannose-introduced experiments (a-c) and effect of depletion (d-f) by flow cytometry as described in Materials and Methods. Depletion of native collectin-11 from MBL-defect serum was analyzed by Western blot under reducing conditions (d: inset). Lane 1 = Recombinant collectin-11; lane 2 = the serum treated with control agarose beads; lane 3 = the serum treated with mannose-agarose beads; serumMBL- = MBL-defect serum; serumMBL-/CL-11- = MBL-defect serum depleted for native collectin-11. Results are representative of three independent experiments that yielded similar results.