CXCL9 and congenital rubella syndrome: Many of the factors in cluster 2 are involved in innate immune responses and have been identified as mediators of cytokine release syndrome (CRS/cytokine storm), including IL-6, IL-10, IL-18, CXCL13, CXCL8, CXCL9, CXCL10, CCL2, CCL4, and TNFα (23).