Integrating Innate Immunity into a Global “Systems” Context: The Complement Paradigm Shift - Systems Biology: Networks, Models, and Applications - page 170

Figure 6.1 Schematic illustration of the complex network of protein-protein
interactions that regulate the activation state of the complement system. This
innate immune system comprises more than 30 soluble proteins and receptors
that play important roles in innate and adaptive immune pathways and also
participate in various immunoregulatory processes. Complement activation
initiates a cascade of proteolytic cleavages that lead to the release of several
bioactive fragments that mediate diverse functions in normal physiology and
disease. All activation pathways converge at the level of C3, a multifunctional
protein that constitutes the central component of the system. Recent evidence
suggests that several key components of the system interact with cellular
networks and signaling pathways that modulate cell differentiation, cell survival,
hematopoietic development, and organ/tissue regeneration. The involvement of
specific complement proteins in such noninflammatory pathways is discussed in
various sections of this chapter.
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