Expression of mRNA levels of HLA-DRA in relation to monocyte HLA-DR: a longitudinal sepsis study

Introduction

Decreased monocyte surface HLA-DR (mHLA-DR) measured by flow cytometry (FCM) is an independent marker of immunosuppression in sepsis. In a previous report we demonstrated that septic patients display a strong correlation between mHLA-DR and mRNA-levels of HLA-DRA in whole blood [1]. mRNA-based HLADR monitoring by PCR would improve the clinical usage and facilitate conduction of multicentre studies. The primary focus in this study was to evaluate the correlation between mHLA-DR and HLA-DRA at different time points during sepsis. In addition, we assessed the dynamic expression of both mHLA-DR and HLA-DRA, in relation to sepsis severity.

Methods

Study patients (n = 54) were included at day 1 to 2 after hospital admission if blood cultures turned positive. Repeated sampling at days 1 to 2, 3, 7, 14 and 28 was performed. mHLA-DR was monitored by FCM and HLA-DRA by quantitative RT-PCR. Mixed models for longitudinal data were used after logarithmic transformation to calculate the interactional effects of time and severity on HLA-DR expression.

Results

Correlation between mHLA-DR(FCM) and HLA-DRA(PCR) at day 1 to 2 (R = 0.78) and day 14 (R = 0.27). Both HLA-DR markers increased linearly on a log scale over time. The linear association was significantly different between the severe (n = 16) and nonsevere septic patients (n = 38) when measuring either mHLA-DR(FCM) or HLA-DRA(PCR). By pairwise comparison of means between the two severity groups, at every time point, the differences between groups were shown to be significant at days 1 to 2 and 3 when monitoring mHLA-DR(FCM) and at days 1 to 2, 3 and 7 for HLA-DRA(PCR) (Figures 1 and 2).

Figure 1

Box plots of mHLA-DR, measured by flow cytometry.

Figure 2

Box plots of HLA-DRA, measured by qRT-PCR.

Conclusion

The correlation between flow cytometry and PCR-based HLA-DR monitoring is stronger in the early phase of sepsis. However, the linear associations over time, in relation to sepsis severity, display similar results for both HLA-DR markers. HLA-DRA(PCR) as a biomarker could be an alternative approach in monitoring immune status in sepsis but needs to be evaluated in relation to clinically relevant immunosuppression.