PMNs were the major source of LTB4 in zymosan-induced lung inflammation. Mice were sequentially injected intraperitoneally with anti-Ly6G/isotype and anti-rat κ light chain, followed by IN instillation of 20 µg zymosan. (A) After 14 hours, total WBCs, percentage of PMNs, and absolute neutrophil count (ANC) were determined in peripheral blood by complete blood count and differential. (B) Cell counts from 3 mL BAL. Cell composition was analyzed by Cytospin with Wright-Giemsa stain. (C) LTB4 levels in the first milliliter of BAL fluid supernatant was measured by ELISA. (D) Lung cell counts from the right lung inferior lobe. The percentage of PMN (CD45⁺Ly6C^intCD11b⁺) was determined by flow cytometry. CD45⁺ cell and PMN counts were calculated by flow cytometry. (E) LTB4 levels in whole-lung homogenate supernatant was measured by ELISA. n = 4 in each group from 2 separate experiments. Data are means ± standard error of the mean. *P < .05; **P < .01; ***P < .001; ****P < .0001, by Student t test.