CHRNA7 and sudden infant death syndrome: Examination of the immunostained preparations revealed a strong immunoreactivity for the nAChR α7 subunit (“Class 3” of nAChR-I) in densely packed cells of compact lung parenchyma areas (Figure 2) and in epithelium surrounding both alveoli and bronchioles (Figure 3) in 22 SIUDS and 8 SIDS victims.