PTX3 expression in BALF cells. Large straight black arrows indicate young neutrophiles, empty arrows indicate macrophages, straight fine black arrows indicate lymphocytes and angled black arrows indicate mature neutrophiles. PTX3 immuno-staining appears in red. (A) BALF cells from a healthy horse at pasture. (B) BALF cells from a healthy horse after two weeks of dust exposure. (C) BALF cells from an R.A.O.-affected horse at pasture. (D) BALF cells from an R.A.O.-affected horse after two weeks of dust exposure. (E) BALF cells from the same horse (R.A.O.-affected horse after two weeks of dust exposure) as in (D) butusing an IgG2B isotype control (control experiment; similar results were obtained by omitting the primary antibody). Magnification ×200. (A color version of this figure is available online at www.vetres.org.)