Fluorescence measurements were performed with a PerkinElmer LS55 fluorescence spectrometer (PerkinElmer). Emission spectra were collected at 25uC using an emission wavelength of 400-600 nm with an excitation wavelength of 380 nm [66] . Apoprotein (5 mM) was mixed with 500 mM ANS in 20 mM sodium acetate buffer (pH 6.5). Zn 2+ and Mn 2+ were added to the mixture of 5 mM apo-SsTroA and 500 mM ANS to 10 mM final concentration, and the mixtures were incubated at 25uC for 15 minutes prior to collecting the excitation spectrum.  The complement system The complement system consists of a tightly regulated network of proteins that play an important role in host defense and inflammation. Complement activation results in opsonization of pathogens and their removal by phagocytes, as well as cell lysis. Inappropriate complement activation and complement deficiencies are the underlying cause of the pathophysiology of many diseases such as systemic lupus erythematosus and asthma. This review represents an overview of the complement system in an effort to understand the beneficial as well as harmful roles it plays during inflammatory responses. Complement was first discovered in the 1890s when it was found to aid or "complement" the killing of bacteria by heatstable antibodies present in normal serum (Walport 2001 ). The complement system consists of more than 30 proteins that are either present as soluble proteins in the blood or are present as membrane-associated proteins. Activation of complement leads to a sequential cascade of enzymatic reactions (known as complement activation pathways; see below) resulting in the formation of the potent anaphylatoxins C3a and C5a that elicit a plethora of physiological responses that range from chemoattraction to apoptosis. Initially, complement was thought to play a major role in innate immunity where a robust and rapid response is mounted against invading pathogens. However, recently, it is becoming increasingly evident that complement also plays an important role in adaptive immunity involving T and B cells that help in elimination of pathogens (Dunkelberger and Song 2010; Molina et al. 1996) and in maintaining immunologic memory preventing pathogenic re-invasion. Not only is complement involved in innate and adaptive immunity but it is also involved in tissue regeneration, tumor growth (Qu et al. 2009 ) and human pathological states such a atypical hemolytic uremic syndrome, age-related macular degeneration, etc. (Wagner and Frank 2010) .