Fig. 1.— Example of a flow cytometric analysis from a representative sample (from one subject), with plots on the left (a, c, e) showing data from a native and plots on the right (b, d, f) data from frozen aliquots of one sputum sample. Plots a) and b) show CD45 binding versus sideward scatter (SSC), c) and d) forward scatter (FSC) versus SSC, and e) and f) CD4 versus CD3. Plots a) and b) illustrate the first step of gating, with AM indicating alveolar macrophages, M monocytes, G granulocytes and L lymphocytes. CD45‐bright lymphocytes were selected to identify morphologically intact lymphocytes (c, d). Cells from plots c) and d) were then used to define CD4+ cells (e, f) versus CD3. PerCP: peridinin-chlorophyll protein; Cal: calibration beats; APC: allophycocyanin; FITC: fluorescein isothiocyanate.