PMN stands for Polymorphonuclear Neutrophils, which are a type of white blood cell that are the most abundant innate immune cells in the body and act as the first defense against infections. PMN cells are characterized by the presence of granules in their cytoplasm and a nucleus that is divided into multiple lobes. They are also known as polymorphonuclear leukocytes (PMNs) or neutrophils. Recent studies have uncovered the diverse functions of PMN cells and their role in different diseases, such as infectious diseases, autoimmune disorders, and cancer. PMN cells contribute to the pathogenesis of several diseases, such as chronic inflammatory diseases, autoimmune diseases, and cancer, through the overactive immune response or the failure of regular immune mechanisms. Despite advances, there are still challenges to be addressed in the study of PMN cells, including understanding the precise mechanisms of PMN cell action, investigating the crosstalk between PMN cells and other immune cells, and identifying the factors influencing PMN cell function.