[Interaction of the 3rd component of complement (C3) with the surface of LS murine fibroblasts]

LS fibroblasts grown in suspension culture fix C3 on their surface when they are incubated with human or guinea pig complement as shown by reacting te cells with FITC-labelled anti C3c sera or immunoglobulins. At the same time the lytic activity of complement is lowered and aliquots of C3 are subtracted from the sera following incubation with the cells. EDTA - EGTA experiments and other observations suggest that C3 fixation requires activation, which proceeds via the alternative pathway, in much the same manner as it has been reported for limphoid cells and thymocytes.