CXCL9 and macrophage activation syndrome: Figure 2. Among cytokines, TNF-α is of particular significance as it is characteristic of SLE-MAS rather than other inflammatory diseases (71, 73). The importance of tumor necrosis factor is also reported in a recent study comparing cytokine levels in SLE patients with and without MAS. The same study has additionally shown that CXCL9 is likewise significantly elevated in SLE-MAS (74).