Figure 9.

Model detailing the impact of C5a/C5aR1 axis activation in C5aR1⁺ cDCs on the activation of antigen specific CD4⁺ T cells. (A) Low potency of C5aR1⁺ cDCs to drive proliferation of antigen specific CD4⁺ T cells. C5a-mediated activation of C5aR1 suppresses the expression of CD40 in MHC-II^lo C5aR1⁺ cDCs. Under such conditions CD40 is critical for cDC-driven proliferation of antigen-specific T cells. (B) C5aR1-targeting of C5aR1⁺ cDCs increases their potency to drive CD4⁺ T cell proliferation. The lack of C5aR1 signaling results in increased CD40 expression in MHC-II^lo C5aR1⁺ cDCs leading to improved synapse formation and stronger T cell activation.