Functional characterisation of interphase neutrophils in sepsis. (A) Microscopic evaluation of total interphase cells, enriched CD66b + interphase neutrophils (CD66b+), and polymorphonuclear neutrophils (PMN) (from the bottom fraction) from a single representative septic shock patient. (B) Total interphase cells were depleted of interphase neutrophils (leaving PBMC), and the enriched CD66b + interphase neutorophils were returned at 6%, 22%, 66% and 94% to PBMC. After 48 hours of culture, there was an inverse association between gated T cell zeta-chain expression (left axis, filled circles) and culture L-arginine concentrations (right axis, empty triangles). (C) Proliferation of interphase cells, gated only on T cells, from a representative severe sepsis patient (grey fill) and enhanced proliferation (left shift) after depletion of interphase neutrophils (black solid line). Plots represent a minimum of 50,000 T cells per condition. Enhanced proliferation remained with addition of PMN (from bottom fraction, black dashed line) at a ratio of 1:2. Control, unstimulated interphase cells are designated by the dotted line. (D) Lymphocyte and CD4 T cell and CD8 T cell division of interphase cells from severe sepsis patients before and after CD66b + depletion.