Primary Immunodeficiency Diseases (PID) represent a group of inherited defects of the genes encoding molecules that are essential for the normal function of immune system. The hallmark of immunodeficiency is susceptibility to infections. These are unusually severe, prolonged infections which require intensive treatment with multiple antibiotics, opportunistic infections or infections with unusual microbial pathogens.
Currently over 250 gene defects were identified whose mutations lead to inadequate protein production and subsequent dysfunction of the immune system. The mutations are inherited in an X-linked, autosomal recessive or autosomal dominant fashion. They commonly cause complete absence or relative insufficiency of the protein encoded by affected gene, but also overproduction or production of the dysfunctional protein. These gene defects affect phagocytic cells, complement system, Toll like receptors, T-cells, B-cells, cytokines and growth factors. Many of these molecules are expressed on the surface or in the cytoplasm of immune cells and could be detected by specific monoclonal antibodies and multiparameter flowcytometry. Furthermore, flowcytometry has been increasingly used for functional assessment of the immune system. Multiple functional assays have been adapted for flowcytometry platform including T cell proliferation, NK cytotoxicity, phagocytic oxidative burst and degranulation, opsonisation or chemotaxis assay and have found its use as screening or diagnostic tools in patients with suspected PID.
An overview of the use of flowcytometry for screening and diagnosis of PID in specific clinical cases will be presented.