Characterization of Serum Complement Activity of Broad-Snouted Caiman (Caiman latirostris, Crocodylia: Alligatoridae)

Abstract

Characterization of the serum complement activity of the broad-snouted caiman Caiman latirostris (Crocodilia: Alligatoridae). Zoological Studies 49(1): 64-70. The sheep red blood cell (SRBC) hemolysis assay was used to detect and characterize complement-system activity of broad-snouted caiman (Caiman latirostris) serum. The hemolytic activity of caiman serum was inhibited by 2 classic inhibitors (EDTA and heat) suggesting the existence of complement-system activity. In addition, we found that the capacity of C. latirostris serum to disrupt SRBCs was concentration, temperature, and kinetics dependent. Hemolytic activity was detected from a very low concentration (< 10%) of caiman serum and increased until 100%. Temperature influenced the activity of the serum by disrupting SRBC membranes. The serum showed a peak of hemolysis between 30 and 40°C, within which lies the optimal temperature caimans prefer during thermoregulation for normal physiological processes. Hemolytic activity rapidly occurred at 2 min, and maximum activity was detected at 60 min. These observations reflect previously reported findings in other crocodilian species (Alligator mississippiensis, Crocodylus johnstoni, and Cro. porosus), thus adding to the knowledge of the role of the complement system in immunological activities of crocodilians.