Human Complement Component C5a (C5a) is also known as C5,and is a protein fragment released from complement component C5.,is a potent chemotactic factor for human peripheral blood neutrophils and monocytes, and is believed to play an important role in a number of inflammatory conditions. There are several functions in the below: C5a is an anaphylatoxin, causing the release of histamine from mast cells; C5a is effective leukocyte chemoattractants, causing the accumulation of white blood cells, especially neutrophil granulocytes, at sites of complement activation; C5a activates white blood cells by increasing avidity for white blood cell integrins and upregulating the Lipoxygenase pathway for arachidonic acid metabolism; C5a is a powerful inflammatory mediator, and seems to be a key factor in the development of pathology of many inflammatory diseases involving the complement system; C5a modulates balance between activating versus inhibitory IgG Fc receptors on leukocytes, thereby enhancing autoimmune response.