TITLE:
Characterization of serum complement activity in serum of the Komodo dragon (Varanus komodoensis)
AUTHORS:
Mark Merchant, Danyell Henry, Rodolfo Falconi, Becky Muscher, Judith Bryja
KEYWORDS:
Innate Immunity; SRBC Hemolysis Varanid
JOURNAL NAME:
Advances in Biological Chemistry,
Vol.2 No.4,
November
21,
2012
ABSTRACT: Incubation of different volumes of serum from the Komodo dragon (Varanus komodoensis) with sheep red blood cells (SRBCs) resulted in volume-dependent hemolysis, as measured spectrophotometrically at 540 nm. The hemolysis occurred rapidly, with almost 90% of the hemolytic activity occurring within 20 min of incubation. A thermal profile showed that Komodo dragon serum exhibited low activity from 5- 20℃, but exerted maximum activity at 35℃, which was substantially reduced at 40℃. The maximum activity was observed near optimal temperatures to which Komodo dragons thermoregulate. Mild heat treatment of Komodo dragon serum (56℃, 30 min) depleted the ability to hemolyze SRBCs. In addition, preincubation of Komodo dragon serum with only 5 mM EDTA or phosphate, both chelators of divalent metal ions, reduced the hemolytic activity sharply. These results indicate that the hemolytic activity was due to the presence of a potent serum complement system. Incubation of Komodo dragon serum with 5 mM EDTA and 15 mM Ca2+ or Mg2+, but not Ba2+, Zn2+, or Fe2+, completely restored activity. These results indicate that Komodo dragon serum complement activity requires the presence of Mg2+ or Ca2+. This is the first assessment of innate immune activity of a Varanid.