Figure 7.

Local synthesis of C3 by antigen presenting cells (APC) is implicated in antigen-specific T cell response. C3 synthesis by APC in case of pathogen internalization induces late apoptotic cargo and allows high expression of MHC on APC surface. Thus, it participates in antigen-specific T cell proliferation and Th1 generation. Local C3 and C5 generate C3a and C5a, which induce up-regulation of Bcl-2 and down-regulation of FAS expression via C3aR and C5aR to facilitate T cell proliferation. Moreover, C3a/C3aR and C5a/C5aR signaling pathways activation promotes Th1 generation and avoid Treg differentiation.