Serial biopsy sections from either control or ALI subjects were stained for evaluations of eosinophil tissue infiltration. Representative photomicrographs of H&E stained slides as well as lung sections subjected to EPX-mAb immunohistochemistry are shown in Figure 1 . The quantitative evaluations of eosinophil density using both staining methods are presented as individual patient assessments in the histograms of Figure 2 . As expected, the evaluation of the H&E stained patient biopsies revealed little evidence of eosinophil infiltration in both control and ALI subjects (0.02 infiltrating eosinophils/ hpf and 0.04 infiltrating eosinophils/hpf, respectively). However, evaluation by the same pathology investigators of the serial slides subjected to EPX-mAb immunohistochemistry demonstrated an enhanced sensitivity to detect eosinophils in these lung tissue sections. Specifically, evaluations of the lungs of control subjects using EPX-mAb immunohistochemistry revealed a >40-fold increase in the ability to detect tissue infiltrating eosinophils relative to H&E staining (0.81 eosinophils/hpf vs. 0.02 eosinophils/hpf, p < 0.01).