It is well known that when macrophages are stimulated with endotoxin, they produce a wide variety of cytokine mediators, including TNF-α and IL-1β. However, there is an alterationnin the macrophages responsiveness when they are challenged with repeated bouts of endotoxin, termed 'endotoxin tolerance' which is regarded as a self-protective phenomenon from continuous stimulation. In this study, endotoxin tolerance in the peripheral blood monocytes of sepsis patients was evaluated.

Fourteen patients with organism-documented sepsis were included. The severity of illness was evaluated by APACHE IIscore. Peripheral blood monocytes were isolated from the patients and diluted to 1×10⁵/well. After stimulation with endotoxin(LPS of E. coli O114:B4, 100 ng/ml), they were incubated at 37℃ in 5% CO2 incubator for 24 hours. Supernatant was collected for the measurement of TNF-αand IL-1β with ELISA method. Peripheral blood monocytes of seven healthy volunteers were used as control.

The APACHE IIscore(mean±SD) of the patients at the time of blood sampling was 12.2±5.7. The primary infection foci were urinary tract infection, pneumonia, subacute bacterial endocarditis, and catheter related infection, etc. The causative organisms were gram negative rods(10 cases), gram positive cocci(6 cases) with two cases of mixed infection. Serum TNF-α could be measured in 4 cases with 29.9±27.7 pg/ml. Serum IL-1β was measureable in only one patient. The TNF-α level of supernatant of cultured peripheral blood monocytes was 2,703±2,066 pg/ml in patients and 2,102±1,914 pg/ml in controls. The IL-1β level of supernatant was 884±1,050 pg/ml in patients and 575±558 pg/ml in controls. There was no difference of TNF-α and IL-1β level between patients and controls.

We cannot prove the phenomenon of endotoxin tolerance in this study. Future study needs to be focused on the more severe sepsis patients who were taken for sampling earlier. Addition of serum to the culture medium could be an another valuable option for the success of this study.