Abstract
Serum complement in the serum of two divergent Central African crocodiles, the African dwarf crocodile (Osteolaemus tetraspis) and the slender-snouted crocodile (Mecistops cataphractus) was assessed using a sheep red blood cell (SRBC) hemolytic assay. The hemolysis for both crocodilian species was serum volume-, time-, and temperature-dependent. Although the serum volume-dependent activities were similar for both species (CH50 = 81 μL for Osteolaemus tetraspis and 96 μL for Mecistops cataphractus), the kinetic curves show a greater amount cooperativity, and thus more rapid SRBC lysis, for Osteolaemus tetraspis. In addition, the hemolytic activities were very similar at 10 – 35°C, but the serum from Osteolaemus tetraspis was more active than that of Mecistops cataphractus at the temperature extremes tested (5°C and 40°C). The activities for both species were almost completely inhibited by 1 mM EDTA, indicating the dependency on divalent metal ions. However, the EDTA-inhibited hemolysis could be restored by the addition of excess Mg2+ and Ca2+, but not Ba2+, Cu2+, or Fe2+, which exhibited the specificity for Mg2+or Ca2+. These data indicate that these sympatric, but evolutionarily and ecologically divergent crocodile species have similar SRBC hemolysis activities with similar mechanisms, thus reinforcing the idea that serum complement is an ancient, innate immunity host defense system.
Highlights
Serum complement is a key component of innate immunity that can be found in all vertebrates and many ancient invertebrates [1,2]
Mutations in mammalian serum complement proteins result in serious clinical conditions [4], and acquired serum complement deficiencies can result in a plethora of disease states [3]
Serum complement can be activated by three distinct mechanisms: 1) the classical mechanism, which relies on the interaction of antibody: antigen complexes, 2) the lectin pathway, which is dependent upon common microbial surface carbohydrate pattern recognition, and 3) the alternative pathway, which is activated by the cleavage of an internal thioester in a specific protein component in response to foreign antigen
Summary
Serum complement is a key component of innate immunity that can be found in all vertebrates and many ancient invertebrates [1,2]. Serum complement can be activated by three distinct mechanisms: 1) the classical mechanism, which relies on the interaction of antibody: antigen complexes, 2) the lectin pathway, which is dependent upon common microbial surface carbohydrate pattern recognition, and 3) the alternative pathway, which is activated by the cleavage of an internal thioester in a specific protein component in response to foreign antigen All three of these complement activation mechanisms involve a proteolytic cleavage cascade of common components, and eventually culminate in the formation of a multiprotein “membrane attack complex” in the outer envelope of microbes, which compromises the integrity of the membrane, and results in eventual lysis. Complement protein C4a mediates inflammation [10] by activation of phagocytic cells, stimulation of the release of granule-based enzymes, and generation of oxidants [11]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Entomology, Ornithology & Herpetology: Current Research
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
