Characterization of serum complement activity in serum of the Komodo dragon (Varanus komodoensis)

Mark Merchant, Danyell Henry, Rodolfo Falconi, Becky Muscher, Judith Bryja

Department of Chemistry, McNeese State University, Lake Charles, USA.
Department of Herpetology, Houston Zoo, Houston, USA.
Department of Herpetology, San Antonio Zoo, San Antonio, USA.

DOI: 10.4236/abc.2012.24043                

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.

Keywords

Innate Immunity; SRBC Hemolysis Varanid

Conflicts of Interest

The authors declare no conflicts of interest.

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