Cover: (A-D) The predominant LTC4S-containing cells (green in A and B, arrows) were not eosinophils (red in A and C, arrowheads), although LTC4S positivity was observed on some eosinophils (cells labeled c and d in A). Digital image analysis with three-color line scan (D) of two non-eosinophils (mast cells labeled a and b in A) and two eosinophils (labeled c and d in A) illustrated the intensity and location of the perinuclear LTC₄S immunoreactivity (green line in D) in these cells. Note the lack of reactivity in one eosinophil (unlabeled red cell in A). (E-G) These strong LTC₄S-immunoreacting cells (green in E, arrows) were mast cells as they co-expressed c-kit (red in F and G, arrows). Note the LTC₄S-negative eosinophils, which are visualized by their prominent granules in DIC microscopy (G, arrowheads). (H-J) Similar results were observed in GMA-embedded acetone-fixed specimens, where the dominating LTC₄S-expressing cells (green in H and J, arrows) were not eosinophils as they were mAb EG2-negative (red in F and G, arrowheads). (K-P) Although the anti-LTC₄S-peptide_37-51 antiserum predominantly identified mast cells (green arrowed cell in K and M) and not eosinophils (mAb EG2 + red cells in L and M) in untreated aspirin-tolerant patients with asthma, it detected such immunoreactivity (green cells, arrowheads in N) in bronchial eosinophils (mAb EG2+ red cells, arrowheads in N, O, and P) in the aspirin-intolerant patients. Note the strong green LTC₄S-immunoreactivity in non-eosinophils (one is arrowed in N and P) which represented LTC₄S-expressing mast cells. Digital multi overlay images from three-color immunohistofluorescence labeling for LTC₄S (anti-LTC₄S-peptide_31-51 antiserum, green); eosinophils (red mAb EG2+ cells in A, C, I, J, L, M, O, and P); or mast cells (c-kit, red in F and G), and nuclei (DAPI, blue), superimposed on diffraction interface contrasted (DIC) images in A, G, J, M, and P. Bronchial cryosection from treated (H-J) and untreated aspirin-tolerant patients with asthma (A-C; E-G; K-M) and one aspirin-intolerant patient (N-P). Panels J, M, and P are not shown on cover. For more information see article by Cai and colleagues beginning on page 683.