Schematic diagram of a hypothetical FXII, HK, gC1qR, PK (FXII-HK-gC1qR-PK) complex with a 1:2:6:2 stoichiometry. In this proposed model, gC1qR is capable of stimulating reciprocal FXII-PK activation by aligning the activation loops and active sites of the FXII and PK proteases. This results in efficient contact system activation, which then drives inflammation and coagulation. The figure has been adapted from Figure 6 in the article by Kaira et al that begins on page 1685.