Complement recognition component

Ligand recognition/binding The carbohydrate content of antibodies, for example, plays a role in antibody binding to monocyte Fc receptors and interaction with complement component Clq... 

Figure 1.15. Complement activation via the alternative pathway. Always present in serum are trace amounts of C3b, which may attach to recognition sites on, for example, yeast cell walls. C3b may combine with serum factor B to form C3bB, and this complex is acted upon by factor D to form C3bBb. This latter complex is a C3 convertase and may act upon C3 to form more C3b to amplify the process. The C3bBb-coated particles may activate other complement components (C4-C9) or be recognised by complement receptors on neutrophils.

Principally because of this latter reason, these pharmacologically active components of complement are attractive as molecular adjuvants. This is because their use has the potential of enhancing specific pathways of the innate and acquired immune processing and subsequent recognition of an Ag as opposed to the broader and less Ag-focused activation of the innate system in response to bacterial signals that come from of adjuvants derived from bacterial components. 

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