Background Many significant evidences implicate interleukin-17 (IL-17) in inflammation, autoimmunity, and defense against some bacteria. One of the chronic autoimmune diseases in which IL-17 might be involved in is systemic lupus erythematosus (SLE). Evidences have identified IL-17 as a key player in the pathogenesis of SLE. Aim of the study The aim of this study was to verify how IL-17 was involved in the immune response in patients with SLE. Patients and methods Forty diagnosed cases of SLE and 20 apparently healthy individuals serving as a control group were recruited for this case–control study from Benha University Hospital and Benha Teaching Hospital. Sterile peripheral blood samples were collected from the study group and the percentage of IL-17 expressing T-cell subpopulation was determined by using flow cytometry. Results After suitable statistical analysis, our results showed a high percentage of intracellular IL-17 in SLE patients and a high statistical increase in the intensity of IL-17 in CD3+, CD4+, and CD8+ T cells in SLE cases when compared with the control group