Brefeldin A, but not monensin, enables flow cytometric detection of interleukin-4 within peripheral T cells responding to ex vivo stimulation with Chlamydia trachomatis

► Brefeldin A (BFA) traps IL-4 within chlamydial-specific T cells. ► Monensin (MN) or BFA and MN prevents intracellular IL-4 accumulation. ► Simultaneous use of both inhibitors can be detrimental to ICS assays.