HALO® is unique in that it can be used to measure a number of parameters from the same sample target cell population. Here are a few examples.
Example 1.
Cell populations can be detected for their response to virtually any agent. If the mechanism of action of cytotoxicity is unknown, it is possible that the cells enter apoptosis. Since the signal detection system used for HALO® (and for LUMENESC™ and LumiSTEM™) measures intracellular ATP concentrations, and ATP is required for the initiation of apoptosis, both cytotoxicity and apoptosis/necrosis can be detected simultaneously using a simple kinetic method.
Example 2.
In a mixed population of cells such as a human bone marrow, peripheral blood or cord blood mononuclear cell preparation, some cell populations may be affected to a greater extent than others by a specific agent. Cytotoxicity can be detected for specific lympho-hematopoietic cell populations, but phenotypic analysis may also help to home in on one or more populations that are affected. By increasing the number of replicates, a portion of these can be used to detect cytotoxicity, while the cells in the rest of the unused wells can be removed and phenotypic analysis performed to determine which populations are affected. Cytotoxicity and phenotypic analysis can then be correlated.
Example 3
In a similar manner to detecting cytotoxicity and performing phenotypic analysis, cells can also be subjected to gene expression marker analysis using PCR etc. Again, only the number of replicates setup for a particular study changes. In this way cytotoxicity, phenotypic expression and genetic expression in response to an agent can be performed.
Example 4.
Furthermore, if phenotypic analysis is undertaken, the HemoGenix® OxyFLOW™ Platform to detect oxidative DNA damage can be incorporated into the flow cytometric protocol. The OxyFLOW™ platform detects oxidative DNA damage using a FITC-conjugated binding protein that specifically binds to 8-oxoguanine residues. Since only one channel of the flow cytometer is used to detect changes in fluorescence intensity, cells can be labeled with as many fluorochrome membrane expression markers that are available for detection by the flow cytometer. Thus, many specific cell populations can be detected.
Example 5.
All of the above possibilities are available for both the LUMENESC™ and LumiSTEM™ Platforms thereby allowing the investigator to perform these and other assays on multiple cell populations from different cell systems. This is the basis of the ComparaTOX™™ Platform for In Vitro, Cross-Platform Comparative Toxicity Testing described later in this Application Section.