Qualitative and quantitative assessment of C3-receptor reactivities on lymphoid and phagocytic cells

Highly purified human C3, free of C5 and beta 1H, was used to prepare EAC14oxy23b, EAC14oxy23b' (C3b cells treated with purified C3bINA and beta 1H) and EAC14oxy23d (C3b' cells treated with trypsin). These intermediates were used to assess by rosette formation C3-receptor activity on various cells. The number of cell-bound C3 per C3b, C3b', and C3d cell was quantified by applying 14C-formaldehyde-labeled C3. Human PBL reacted to about the same degree with C3b, C3b', and C3d cells, whereas monocyte-free PBL enriched for B cells interacted preferentially with the C3b' and the C3d cells; human tonsil lymphocytes behaved similarly. The reaction of Raji cells was clearly assessable with C3b cells and was accelerated with C3b' and C3d cells. Daudi cells reacted with C3b' and C3d cells only, in comparison to Raji cells with a much lower activity. Human granulocytes reacted equally well with C3b and C3b' cells, but towards C3d cells they were almost unreactive. Human monocytes formed rosettes with C3b cells, and at a lower level, rosettes with C3b' cells. C3d cells were unreactive. Similar reaction patterns were obtained with guinea pig leukocytes, whereas mouse leukocytes were totally different, since peritoneal macrophages only formed rosettes with human C3b' cells.