Polymorphonuclear leukocytes and γδ T lymphocytes acquire the ability to bind to biotinylated PTX3 only when undergoing late apoptosis in vitro.

Human polymorphonuclear leukocytes were purified from peripheral blood and allowed to undergo apoptosis in vitro. (A) The early apoptotic cell population, identified after 16 hours as annexin V⁺ cells that excluded PI did not bind to biotinylated PTX 3 (y-axis, mean fluorescence intensity). (B) Upon prolonged in vitro culture (72 hours), polymorphonuclear leukocytes lost the ability to exclude PI and acquired the ability to bind to biotinylated PTX3. (C) The ability of nontransformed γδ T cells to bind to PTX3 was assessed by flow cytometry after apoptosis induced by CD95 cross-linking or recognition of the tubercular antigen isopentenylpyrophosphate. Results of the binding of cells undergoing early apoptosis (PI⁻, □) or late apoptosis (PI⁺, ■) are reported as RFI (y-axis), calculated by dividing the mean fluorescence intensity in the presence of biotinylated PTX3 and FITC-streptavidin with that obtained in the presence of FITC-streptavidin alone.