Humoral immune system and ulcerative colitis activity. II. Complement level.

C4, C3 and C5 levels and the complement hemolytic activity were analysed in 84 ulcerative colitis patients and correlated with activity, extension and duration of the disease, with the presence of extraintestinal manifestation, and with therapeutic effects. The elevation of C3 was observed in both mild active and in severe colitis. Only C3 correlated with disease activity and with C-reactive protein level. On the other hand, C4 and C5 levels were significantly decreased in the active disease extended to the left side or to total great bowel. The importance of these findings is discussed. No significant connection of the examined complement components with duration, therapy and extraintestinal manifestation was observed. A trend to increase the complement hemolytic activity in severe colitis was noted. Our study of complement and its components activity suggests the secondary role of analysed parameters in pathogenesis of UC and clinical usefulness of C3 level as an indicator of the disease activity.