Flow cytometry and immune disorders

Abstract

cytometry (FCM) is the natural technical tool to mea-sure cells of the immune system in health and disease. By itsability to rapidly measure millions of individual cells it allowscollection of statistically reliable information from rare cellsubsets. Due to the opportunity to multiplex analysis—by thecombination of manifold markers even on the single celllevel—unequivocal identification of complex cell phenotypesis enabled. Standardization and high level of quality controlallows overall control of the preanalytical and analytical pro-cess and by standardized reporting, the reproducibility byother laboratories. This is an extremely important issue inclinical diagnosis, where right or wrong may decide the fate ofa patient. Several improvements are on their way to improvespecificity by optimized marker combinations and novel tech-nologies.Human peripheral blood monocytes can be subclassifiedby phenotypic markers into three functionally differentsubsets (1). These subsets play different roles in pathologicaldisorders and thus are relevant for diagnosis and immunomo-nitoring. One of the main obstacles in their unequivocal iden-tification is that typical phenotypic cell surface markers suchas CD14 are downregulated in one subset and others (CD16and HLA-DR) are shared by other leukocytes, for exampleNatural Killer and B cells. Furthermore, HLA-DR is downre-gulated in septic patients obscuring identification of activatedmonocytes. Recently, a single platform multicolor assay wasintroduced to quantify these monocyte subpopulations (1).Now, Abeles and colleagues from Imperial College in Londonand Oxford, United Kingdom (this issue, page 823) reducedthe number of required markers for clinical diagnosis for theidentification of various human monocyte subsets to three inorder to analyze peripheral blood monocytes in individualswith acute liver failure. This new critically evaluated panelrelies on the backbone of the above three surface markers anda careful gating strategy allowing the identification of allmonocyte subtypes unequivocally in healthy and severely illindividuals.Several genetic disorders also affect the development andpopulation composition of peripheral blood leukocytes. Manyof these congenital immune defects may lead to severeimmune deficiency, recurrent infections, cancer formation orautoimmune diseases. Pia˛tosa and colleagues from Warsaw,Poland, and Rotterdam, The Netherlands (this issue, page835) looked more closely at the immune system of individualswith Nijmegen Breakage Syndrome who have a preference forlymphoma formation, among others. Blood samples ofinfants, toddlers, children and adults were analyzed regardingabsolute count of B-cell maturation stages by four-colorimmunophenotyping by a single platform assay. The authorsconfirmed the already know reduction in the number of circu-lating B-cells but in addition also reported an arrest in B-celldevelopment leading to an impaired immunoglobulin classshift, low antibody levels and thereby reduced immune defensecapability.The prevalence for Diabetes Mellitus of type 2 (DM2)alarmingly increases worldwide. Today, the disease not onlyaffects the population in the northern hemisphere but alsospreads into India and Asian countries. Furthermore, not onlyadults but also increasingly children are affected. This ismostly due to the elevation in childhood obesity. Accompany-