Glomerular Complement Components

sies studied by immunofluorescence contained varying combinations of immunoglobulins (Ig), complement (C) components Clq, C3, C4, C5, C6, C8, C3 proactivator (C3PA), and/or properdin. 10 patients had linear de-posits of Ig in glomeruli characteristic of antiglomeru-lar basement membrane (GBM) antibodies; nine pa-tients had C3 deposits (minimal in three) with generally lesser amounts of Clq, C4, C5, C6, and/or C8. 118 of the patients had granular deposits of Ig, suggesting im-mune complex glomerulonephritis; 114 of these had de-posits of C3, usually accompanied by Clq, C4, C5, and/ or C6. These observations indicate that the entire C sequence is deposited in glomeruli in most Ig-mediated glomerulonephritides. However, certain cases of anti-GBM glomerulonephritis with few or no C deposits may utilize pathways of injury independent of C. 21 patients had granular C3 deposits without detec-table Ig. C5, C6, and C8 were present in the majority of these patients while Clq was absent and scant C4 was observed in only two patients. The presence of only late-acting C components in the absence of Ig, Clq, and C4 suggests selective, possibly nonimmune activation of the alternate C pathway. Finally, five patients had granular deposits of C3, C5, C6, and/or C8 diffusely in all or most glomeruli with a lesser number of glomeruli having additional focal granular deposits of Ig, Clq, and C4. This observation suggests that at least two patterns of C activation can occur simultaneously, possibly trig