The results of studies on the CD3(+)CD8(+)CD28(-) cells in SLE are inconsistent since several analyses describe CD3(+)CD8(+)CD28(-) as either immunosuppressive or cytotoxic. The aim of this study is to inquire whether the quantitative changes of CD3(+)CD8(+)CD28(-) T lymphocytes subpopulation are related to the clinical status of patients with lupus nephritis. Evaluation of Foxp3 expression on CD3(+)CD8(+)CD28(-) cells may shed some light on functional properties of these cells. 54 adult SLE patients and 19 sex and age matched healthy volunteers were enrolled in the study. There were 15 patients in inactive (SLEDAI ≤ 5) and 39 in active (SLEDAI > 5) phase of disease. We determined absolute count of CD3(+)CD8(+)CD28(-) and CD3(+)CD8(+)CD28(-)Foxp3(+) subpopulations by flow cytometry. We observed a statistically significant increase in absolute count and percentage of CD3(+)CD8(+)CD28(-) in SLE patients compared to HC (p < 0.001). Moreover there was significant positive correlation between increasing absolute count of CD3(+)CD8(+)CD28(-) cells and disease activity measured by SLEDAI (rs = 0.281, p = 0.038). Active LN patients had increased absolute count of CD3(+)CD8(+)CD28(-) cells compared to HC. Positive correlation of CD3(+)CD8(+)CD28(-) number with disease activity, and lack of Foxp3 expression on these cells, suggests that CD3(+)CD8(+)CD28(-) lymphocytes might be responsible for an increased proinflammatory response in the exacerbation of SLE.