The complement system's activity in human disease can be detected using more informative assays, such as those that identify bypass pathways. These pathways, which are often overlooked, play a critical role in disease mechanisms. For example, C4-deficient animals are commonly used to rule out the classical or lectin pathways, but bypass pathways may be active in "deficient" states. These pathways can be triggered by natural antibody responses to infections, and current methods do not analyze them in clinical settings or animal models. The IL-23/IL-17 axis is a key player in inflammation and autoimmune diseases. IL-23 induces the differentiation of naive CD4+ T cells into Th17/ThIL-17 cells, which produce IL-17, IL-17F, IL-6, and TNF-α. Two studies in this issue show that blocking IL-23 or its downstream factors significantly suppresses disease in models of inflammatory bowel disease and MS. These findings suggest that the IL-23/IL-17 pathway is a promising therapeutic target. Th17/ThIL-17 cells are a distinct subset of CD4+ T cells that produce IL-17. They play a critical role in autoimmunity and allergic reactions. IL-23 is essential for the development of these cells, and its inhibition reduces inflammation. The IL-23/IL-17 axis is distinct from the IL-12/IFN-γ pathway, which is more involved in intracellular pathogen defense. IL-23 also contributes to inflammation through IL-17-independent pathways, such as by inducing IL-1 and IL-6 production. The differentiation of Th17/ThIL-17 cells is not fully understood, but factors like T-bet and STAT3 are involved. IL-23R expression is critical for Th17/ThIL-17 development, and its downregulation by IFN-γ and IL-4 inhibits differentiation. TGF-β can also induce Th17/ThIL-17 cell differentiation in the presence of IL-6. These findings highlight the importance of the IL-23/IL-17 axis in inflammatory diseases and suggest that targeting this pathway may be effective for treatment. Caveolin-1 (Cav-1) is a key component of caveolae, which are involved in the vascular response to shear stress. Yu et al. show that caveolae/Cav-1 may act as sensors of altered shear stress and organize the signaling response in endothelial cells. This highlights the role of Cav-1 in regulating the vascular response to hemodynamic forces.The complement system's activity in human disease can be detected using more informative assays, such as those that identify bypass pathways. These pathways, which are often overlooked, play a critical role in disease mechanisms. For example, C4-deficient animals are commonly used to rule out the classical or lectin pathways, but bypass pathways may be active in "deficient" states. These pathways can be triggered by natural antibody responses to infections, and current methods do not analyze them in clinical settings or animal models. The IL-23/IL-17 axis is a key player in inflammation and autoimmune diseases. IL-23 induces the differentiation of naive CD4+ T cells into Th17/ThIL-17 cells, which produce IL-17, IL-17F, IL-6, and TNF-α. Two studies in this issue show that blocking IL-23 or its downstream factors significantly suppresses disease in models of inflammatory bowel disease and MS. These findings suggest that the IL-23/IL-17 pathway is a promising therapeutic target. Th17/ThIL-17 cells are a distinct subset of CD4+ T cells that produce IL-17. They play a critical role in autoimmunity and allergic reactions. IL-23 is essential for the development of these cells, and its inhibition reduces inflammation. The IL-23/IL-17 axis is distinct from the IL-12/IFN-γ pathway, which is more involved in intracellular pathogen defense. IL-23 also contributes to inflammation through IL-17-independent pathways, such as by inducing IL-1 and IL-6 production. The differentiation of Th17/ThIL-17 cells is not fully understood, but factors like T-bet and STAT3 are involved. IL-23R expression is critical for Th17/ThIL-17 development, and its downregulation by IFN-γ and IL-4 inhibits differentiation. TGF-β can also induce Th17/ThIL-17 cell differentiation in the presence of IL-6. These findings highlight the importance of the IL-23/IL-17 axis in inflammatory diseases and suggest that targeting this pathway may be effective for treatment. Caveolin-1 (Cav-1) is a key component of caveolae, which are involved in the vascular response to shear stress. Yu et al. show that caveolae/Cav-1 may act as sensors of altered shear stress and organize the signaling response in endothelial cells. This highlights the role of Cav-1 in regulating the vascular response to hemodynamic forces.