(A) Apoptosis in unstained lung sections by TUNEL assay: (a) untreated (OVA-challenged), (b) unmodified (pure) chitosan nanoparticles, (c) theophylline, (d) theophylline plus pure chitosan nanoparticles, (e) theophylline plus TCNs (top panel: nuclei stained with DAPI; bottom panel: apoptotic cells stained with FITC). (B) semiquantitative analysis of TUNEL positive cells. Examination of tissue sections was performed by different persons in a blinded fashion. The results of a representative experiment of two performed is shown. **p < 0.01, *p < 0.05 compared with TPL.