Figure 2.

Basis of hydroxychloroquine (HCQ) use in rheumatic diseases. The drug in antigen processing cells (APC) – namely plasmacytoid dendritic cells, monocytes, macrophages, and B cells – interferes with toll-like receptor (TLR)-mediated activation, signaling and cytokine production. In APC such as plasmacytoid dendritic cells and B cells, the drug inhibits antigen processing and subsequent major histocompatibility complex (MHC) class II-mediated antigen presentation to T cells. This prevents T cell activation, production of proinflammatory molecules and reduces the production of cytokines. Abbreviations: IL-1, interleukin 1; IL-6, interleukin-6; IFNγ, interferons; TNF, tumor necrosis factor; BAFF, B-cell activating factor.