Monocytes caspase-4 correlates with sphingosine-1-phosphate receptor 2 (S1PR2) expression levels in patients with Gram-negative sepsis. (A) Caspase-4 and (B) S1PR2 messenger RNA (mRNA) levels were evaluated using real-time quantitative polymerase chain reaction in monocytes from Gram-negative septic patients and nonseptic controls. β-Actin was used as an internal control. n = 11 for septic patients and n = 8 for nonseptic controls. Values are presented as mean ± SD and were analyzed using Student’s t test for caspase-4 level and Welch’s correction t test for S1PR2 level. (C) Correlations between caspase-4 and S1PR2 expression in the Gram-negative septic patients. Values were analyzed using the Spearman correlation test. *P < 0.05.