B and T lymphocyte attenuator (BTLA) is an inhibitory receptor, whose primary role in CD4⁺ T cell is thought to inhibit cytokine production. We explore BTLA expression on CD4⁺ T cells in healthy controls and septic patients, and assess the correlation of BTLA expression on CD4⁺ T cells in the early stage of sepsis with the severity and mortality of septic patients in the emergency department (ED).

336 consecutive patients were included in this study. BTLA expression on CD4⁺ T cells was measured by flow cytometry within 24h of ED admission.

Our results showed that the percentage of BTLA⁺/CD4⁺ T cells was high expression in healthy volunteers and it was statistically reduced in severe sepsis and septic shock compared with healthy controls(all P<0.01). The area under the receiver operating characteristic (AUC) curves of BTLA expression on CD4⁺ T cells was slightly lower than that of procalcitonin (PCT) and Mortality in Emergency Department Sepsis (MEDS) score. The percentage of BTLA⁺/CD4⁺T cells was lower in non-survivors than in survivors (P<0.01), and similar results were obtained when expressed as mean of fluorescence intensities (MFI) (P<0.01). Adjusted logistic regression analysis suggested that the percentage of BTLA⁺/CD4⁺ T cells was associated with 28-day mortality in septic patients (odds ratio (OR) = 0.394).

Our study shows that the percentage of BTLA⁺/CD4⁺ T cells was high in healthy volunteers. Furthermore, lower percentage of BTLA⁺/CD4⁺ T cells during the early stage of sepsis is associated with the severity and the mortality of septic patients.