Levels of complement C3 and C4 components in Amerindians living in an area with high prevalence of tuberculosis

Abstract

The levels of complement C3 and C4 components were determined in non-indigenous (creoles) and indigenous (Warao) populations, the latter with an extremely high tuberculosis (TB) rate. Serum samples from 209 adults were studied and classified in 4 groups taking into account tuberculin skin tests (TST): (1) the group of Warao patients (58 positive for the TST, WP TST+ and 9 negative for the TST, WP TST–), (2) the group of creole patients (34 positive for the TST, CP TST+ and 9 negative for the TST, CP TST–), (3) the group of healthy Warao controls (38 positive and 14 negative for TST, WC TST+ and WC TST–, respectively), (4) the creole controls (26 positive and 21 negative for the TST, CC TST+ and CC TST–, respectively). With respect to the results concerning the measurement of both complement C3 and C4 components with the exception of the WC TST– and the CC groups, the WP TST+ and WP TST– as well as WC TST+ groups showed a significant frequency of individuals with decreased levels of complement C3 component (20.6, 33.3, and 26.3%, respectively) and also C4 component (12.0, 11.1, and 13.3%, respectively) in comparison to both creole patients (CP TST+, 8.82% and CP TST–, 0% and CP TST+, 5.88% and CP TST–, 0%) for C3 and C4, respectively. The study of these parameters carried out in 15 Warao subjects with active infection, before and after anti-TB chemotherapy, statistically confirmed that the effective chemotherapy did not restore normal levels of the complement C3 and C4 components among Warao patients. Aditional tests for hepatitis B or hepatitis C infection, and the profile of the hepatic proteins were not associated to the deficiency in production of the complement components. In conclusion, the results show that within the Warao population, a high percentage of subjects exhibit decreased levels of both complement C3 and C4 components independent of latent or active infection and the status of TST.