IL-12 and IL-23/Th17 axis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a very complex disease where multiple immunological pathways can concur in inducing tissue damage. Cytokines are key mediators in this process and among them the role of interleukin (IL)-12 and the IL-23/Th17 axis has recently emerged. IL-12 and IL-23 have a heterodimeric structure with a common subunit, named p40. Although they share a partially common structure, their functions appear slightly different. Indeed, IL-12 is a key cytokine in inducing an efficient T helper 1 (Th1) response and in Th differentiation, while IL-23 plays a crucial role in chronic inflammation and Th17 cell activation, which results in IL-17 secretion. The increasing knowledge on the interaction between IL-12 and IL-23/Th17 axis in the development of autoimmune diseases has led to the identification of new therapeutic strategies targeting these immunological pathways. IL-23/Th17 axis has recently been suggested to be essential in developing lupus nephritis, both in mice and in humans. In keeping with these observations, ustekinumab, a fully human IgG1 kappa monoclonal antibody (mAb) directed towards p40 subunit, has been investigated in SLE. Promising data from a phase II randomized controlled trial in SLE patients suggest that this mAb might be a potential novel therapeutic strategy in SLE. In this review, we summarize the complex interaction between IL-12 and IL-23/Th17 axis in SLE with a special focus on drugs which affect this immune pathway. Impact statement Our article is focused on emerging pathogenetic pathways in systemic lupus erythematosus (SLE). Notably, IL-12 and IL-23 have been described as emerging cytokines in SLE pathogenesis. We know that IL-23 stimulates Th17 cells to produce IL-17. We try to point out the importance of IL-23/Th17 axis in SLE and to focus on the interaction between this axis and IL-12. Ustekinumab, a fully human IgG1 kappa monoclonal antibody directed towards the p40 shared subunit of IL-12 and IL-23, has been recently investigated in SLE, suggesting a potential novel therapeutic strategy in SLE. To our knowledge, there are no reviews which simultaneously focus on IL-12 an IL-23/Th17 axis in SLE. Thus, we believe our work will be of interest to the readers.