1482 INTERACTIONS OF HUMAN, CULTURED KIDNEY CELLS WITH THE COMPLEMENT (C) SYSTEM

Abstract

Previously we have shown that C activation takes place when heat-killed, cultured human kidney cells are incubated in normal human serum. C activation initiated by 0.5 × 107 cells/50 μl permitted moderate C4, C2, C3 and C5 consumption of hemolytic activity without detectable loss of Cl and no reduction in C6 activity. At 2 × 107 cells/50 μl serum, some loss of C1 and C6 hemolytic activity was noted. C4 and C2 consumption could not be prevented by blocking primary C pathway through prior EGTA chelation of serum. Both living and heat-killed kidney cells were incubated with normal serum and then examined for surface bound C components using immunofluorescence techniques. The heat-killed kidney cells were strongly positive for C3 which was distributed in a diffuse, speckled pattern over the entire cell surface . Dead cell suspensions also showed weak IgG and Clq immunofluorescence but were negative for surface albumin, C5 and β1H. In contrast, living cell suspensions treated in a similar manner showed only occasional cells immunofluorescent positive for C3, IgG or Clq and all cells were negative for albumin, C5 and β1H. Viability stains run concurrently revealed that the few C3 positive cells in living cell suspensions belonged to the small, nonviable cell subpopulation. These data indicate that dead kidney cells can initiate limited C activation resulting in preferential C3b opsonization of dead, but not living cells.