Fig. 1.

Clearance of apoptotic 5,6 carboxyfluorescein diacetate succinimidyl ester (CFS-E)-labelled Jurkat cells by macrophages in the presence of sera deficient in selected complement components was studied using flow cytometry. A phagocytosis index (PhI) was calculated by comparing the percentage of phagocytizing CD14-positive cells in the presence of test serum with the presence of normal human sera (NHS). A test serum that had the same capacity of facilitating phagocytosis as NHS was consequently given the value 1. Sera from individuals deficient in C1q (C1qD; patient C1q-D1), C4 (C4D), C2 (C2D; patient C2D-1) and C3 (C3D) all showed decreased phagocytosis. Addition of C1q, C4 or C2 all increased the PhI by the same magnitude, while addition of C3 gave less increase. Sera lacking factor D (DD), properdin (PD) or mannose binding lectin-deficient (MBLD) did not show low PhI and only addition of properdin increased PhI further. Mean and standard deviation from three experiments are shown.