Research Report 191 describes a study by Allison Fryer and colleagues that addressed how exposure to ozone affects the immune and physiological responses in guinea pigs. In her study, Dr. Fryer focused on eosinophils, white blood cells that play an important role in inflammation, allergies, and allergic asthma, and can modify the airway response to ozone inhalation. This study tested a novel hypothesis: that allergic guinea pigs react differently to ozone than normal animals because of newly formed eosinophils that migrate from bone marrow to the lungs.