C2 and periodontitis: Differential analysis between the disease cohorts and the healthy controls revealed significant gene expression alterations in patients with periodontitis (Figure 6A,C) and IBD (see Figure 6B,D), predominantly involving genes associated with the immune and inflammatory responses, such as immunoglobulin lambda joining 3 (IGLJ3), C-X-C motif chemokine receptor 4 (CXCR4), CD74 molecule (CD74), complement C2 (C2), among others.