The role of eosinophils in the pathogenesis, diagnosis and treatment of asthma

Cells corresponding to eosinophils were already histopathologically documented in the first half of the 19th century. However, the term "eosinophils" was first used by Paul Ehrlich in 1878. Since the discovery of eosinophils, their existence has been associated with bronchial asthma, allergies and the pathogenesis of helminthic disorders. Since the beginning of the 21st century, understanding this cell population's nature has undergone a fundamental reassessment. In 2010, J. J. Lee proposed the concept of "LIAR" (Local Immunity And/or Remodeling /Repair), underscoring the extensive immunoregulatory functions of eosinophils in the context of health and disease. It soon became apparent that mature eosinophils are not structurally, functionally, or immunologically homogeneous cell populations. On the contrary, they form subtypes characterized by distinct development, immunophenotype, sensitivity to growth factors, localization, role and fate in tissues and their contribution to the pathogenesis of various diseases, including asthma. Resident (rEos) and inflammatory (iEos) eosinophils have recently been proposed for the main eosinophil subsets. It turns out that understanding the functions of eosinophil subpopulations and their identification in tissues is an essential condition for the correct diagnosis, classification and treatment of diseases associated with eosinophils. It can therefore be assumed that new biomarkers revealing these cells' more profound biological nature can significantly expand the existing range of validated parameters monitored in bronchial asthma. Concurrently, they will contribute to more accurate diagnosis and more effective treatment of this disease.

Keywords: biological treatment, biomarkers, bronchial asthma, eosinophils, immunophenotype.