CD27 and Sepsis: We therefore focused on a standardized secretion-focused functional assessment to interrogate released (effector) GzmB as one complementary facet of NK cell function in sepsis, while recognizing that intracellular flow cytometry (ICS) can quantify the intracellular pool at single-cell resolution, link it to maturation/NKR phenotypes (e.g., CD27/CD11b, Ly49), and map subset-level heterogeneity.