Neutrophils (NG) are the most numerous white blood cell population. NG disorders are often associated with failure to carry out preventive vaccinations and/or to a high risk of life-threatening infections (in Poland approx. 3000 children a year). NG contains specialised granules, which include many proteins, including specific neutrophil serine proteases (NSPs). Mutations in NSP genes often lead to neutrophil defects. NSPs are therefore necessary for the maturation and functioning of NG. The main objective of this project is to combine clinical and genetic data with data on the biology of NSPs using highly selective chemical markers to identify their role in NG malfunction. The efforts of three academic centres (FIXNET consortium) will contribute to achieving this objective of the project. This will enable the development of globally unique diagnostic and therapeutic methods of diseases associated with NG dysfunction.