Our aim was to investigate STAT3 phosphorylation in CD4+ T cells, CD8+ T cells, and CD11b+ myeloid cells using single-cell flow cytometry of PBMCs isolated from healthy controls and patients with SLE upon inducing a strong inflammatory response comparable to pathological conditions by IL-6 or IL-15 stimulation ex vivo. The gene discussed is IL6; the disease is systemic lupus erythematosus.