Abstract： Objective To investigate the functional changes of dendritic cells (DC) in elderly patients with sepsis. Method Elderly patients (n = 20), ages 75 to 86 years, treated in the department of internal medicine for cadres and the medical intensive care unit (MICU), were selected to participate in the study. Patients with ma-ligoant tumors, hematological diseases, immune diseases, or a history of receiving drugs known to interfere with immune functions were excluded. Using the American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) definition of sepsis, the patients were categorized into four groups: non-sepsis (group A) (n = 5) ; sepsis (group B) (n = 5) ; severe sepsis (group C) (n = 5) ; and septic shock (group D) (n = 5). The peripheral blood mononuclear cells (PBMCs) of each patient were isolated and cultured with human re-combinant granuloceyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) in vitro for 10 days. The cells were examined under an inverted microscope, scanning electron microscopy, and flow cytometry. The MTT colorimetric assay was used to observe the abilities of the dendritic cells to stimulale an allogeneic T lym-phocyte response in vitro. Paired t -test was used to compare changes in the surface markers among the different groups, Results The PBMCs in the four groups of patients differentiated into cells with typical dendritic configura-tions after in vitro cuhure with combined cytokines. The CD40, CD80, CD86, and HLA-DR expressions on the cell surfaces increased after culture,with (43.2±12.5)%/(27.3±9.3)%, (31.4 ± 10.1)%/(22.5 ± 8.7)%, (39.3±15.7)%/(21.9±7.7)%, and (75.4±25.6)%/(58.7±16.7)%, respectively. The stimulation index (the abilities of the dendritic cells to stimulale the allogeneic T lymphocyte response in vitro) in the four groups of patients after culture were (23.3±7.9) in group A, (18.9±8.3) in group B,(11.4±5.1) in Group C,and (5.5 ± 3.7) in Group D. Conclusions The immune functions of the dendritic cells of elderly patients with sepsis decrease in a linear manner with the severity of their septic state.