Apoptosis Assay Apoptosis, or programmed cell death, is the process by which cells regulate how they die, activating specific pathways that cause the cell to shrink, condense, and eventually be cleared by phagocytosis. This is in contrast to necrotic cell death where cells die uncontrollably and fall apart, which can lead to detrimental effects such as the activation of an immune response. Therefore, apoptotic cells that die in a very orderly fashion limit disruption of nearby cells and tissue. There are many ways to measure cell death and distinguish it from apoptosis or necrosis. These assays are easily quantified using the NovoCyte flow cytometer due to automatic compensation settings and a wide dynamic range of fluorescence detection which eliminates the need for any PMT voltage adjustments.   Immunophenotyping Immune status is associated with disease state, treatment efficiency, and response to external stimuli such as vaccines. Immunophenotyping quickly identifies candidate cell types, sub-classes and functions. Monitoring the frequency of numerous immune cell population as well as the differentiation/activation status of specific cell subsets such as monocytes, NK cells, T and B cells is essential as they may influence the immunogenicity of a vaccine and its efficiency. The NovoCyte Flow Cytometer enables simultaneous quantification of multiple leukocytes for better understanding the immune status of patients and surveillance of the immune response to infectious disease.   Intracellular Protein Detection Detection and analysis of intracellular proteins allow for additional characterization of cell subpopulations and cellular processes. In order to analyze proteins not located on the cell surface, fixation and permeabilization of the cell is required. However, many phospho-specific antibodies are not compatible with many common detergent-based permeabilization methods used for intracellular staining. Special attention is needed when determining the proper fix/perm method for your phospho-specific antibody. The most common method uses 1.5% paraformaldehyde for fixation followed by 100% methanol for permeabilization. While this method works for many antibodies, please note it may not work for every phospho-specific antibody. Additionally, identifying various cell populations in a heterogenous sample requires staining for phosphorylated proteins coupled with surface proteins. Special consideration must be given to the sensitivity of these epitopes to fixative, taking precaution to avoid damage to the epitope. Therefore, the sample may require staining for specific surface markers before fixation.   Cell Cycle Analysis Normal human somatic cells are diploids containing a constant amount of DNA. During cell cycle progression, DNA synthesis results in a doubling of total DNA content, followed by restoration of the normal DNA content after mitosis. Detailed cell cycle analysis can be performed to understand tumor cell differentiation, cell transformation and cell-compound interaction with the NovoCyte flow cytometer.   Cell Proliferation Cell proliferation is an essential function and highly structured event that when unregulated, can cause disease. We can measure proliferation through absolute cell counts or with a dye, such as CFSE. When cells labeled with CFSE divide, the dye is partitioned equally between daughter cells and we can measure the loss of CFSE fluorescence over time as the dye is continuously diluted. The mean fluorescence intensity (MFI) of the dye was also plotted with cell concentration over time to show the inverse relationship between the two. This type of assay is often used to look at changes in T lymphocyte activation.