Circadian rhythms in the human complement system

Single- and population-mean-cosinor analyses of data from a mother and daughter pair in the United States and 16 other women from Italy, all clinically healthy, reveal evidence for circadian rhythms in the third component of complement (C3c). For this group of diurnally active and nocturnally resting (darkness from 2200 to 0500) women, the C3c rhythm characteristics were: amplitude 6.8 mg/dl (3.2 to 11.0 the 95% confidence limits), mesor ± 1 SE of 177 ± 8 mg/dl and acrophase 1500 (1250 to 1825 the 95% confidence limits). For the mother-daughter pair, circadian rhythms were detected also for other aspects of the complement system-factors B and C1 Inh with the acrophase around mid-afternoon.