A likelihood approach to classifying fluorescent events collected by multicolor flow cytometry

Flow Cytometric Analyses of Lymphocyte Markers in Immune Oncology: A Comprehensive Guidance for Validation Practice According to Laws and Standards

Many anticancer therapies such as antibody-based therapies, cellular therapeutics (e.g., genetically modified cells, regulators of cytokine signaling, and signal transduction), and other biologically tailored interventions strongly influence the immune system and require tools for research, diagnosis, and monitoring. In flow cytometry, in vitro diagnostic (IVD) test kits that have been compiled and validated by the manufacturer are not available for all requirements. Laboratories are therefore usually dependent on modifying commercially available assays or, most often, developing them to meet clinical needs. However, both variants must then undergo full validation to fulfill the IVD regulatory requirements. Flow cytometric immunophenotyping is a multiparametric analysis of parameters, some of which have to be repeatedly adjusted; that must be considered when developing specific antibody panels. Careful adjustments of general rules are required to meet legal and regulatory requirements in the analysis of these assays. Here, we describe the relevant regulatory framework for flow cytometry-based assays and describe methods for the introduction of new antibody combinations into routine work including development of performance specifications, validation, and statistical methodology for design and analysis of the experiments. The aim is to increase reliability, efficiency, and auditability after the introduction of in-house-developed flow cytometry assays.

The O-antigen mediates differential survival of Salmonella against communities of natural predators

Antigenically distinct members of bacterial species can be differentially distributed in the environment. Predators known to consume antigenically distinct prey with different efficiencies are also differentially distributed. Here we show that antigenically distinct, but otherwise isogenic and physiologically indistinct, strains of Salmonella enterica show differential survival in natural soil, sediment and intestinal environments, where they would face a community of predators. Decline in overall cell numbers is attenuated by factors that inhibit the action of predators, including heat and antiprotozoal and antihelminthic drugs. Moreover, the fitness of strains facing these predators - calculated by comparing survival with and without treatments attenuating predator activity - varies between environments. These results suggest that relative survival in natural environments is arbitrated by communities of natural predators whose feeding preferences, if not species composition, vary between environments. These data support the hypothesis that survival against natural predators may drive the differential distribution of bacteria among microenvironments.