Flow+Cytometry

Flow cytometry is used to analyze individual cells in a particular sample. A wide range of cell sizes can be examined generally between 1-15 µm in length. The sample is passed through the cytometer at extremely high speeds. A laser is directed onto the stream of liquid which contains these cells. The scattered light that emerges from each cell as it passes through the cytometer is detected, converted to voltage and analyzed. More complex systems with multiple color detectors have been developed.
 * Basic description: **

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Flow cytometry can be used to determine a variety of chemical and physical characteristics of cells. Parameters of flow cytometry include but are not limited to; cell volume, capacitance, light scattering, absorption, extinction, interference, cell size, cell shape, DNA content, total protein, surface antigens, surface charge, endocytosis, cytoskeletal organization, gene expression, oxidative metabolism, pH and enzyme activity. This technique is often used for diagnosis of many diseases, through sorting and purifying particles based on their measured properties.
 * Purpose: **

A primitive form of flow cytometry was introduced in the 1950’s by Wallace Coulter. It involved counting and sorting cells by size, as the cells passed through an electrical current. In the mid 1960’s Mack Fulwyler developed a droplet cell sorter which separated cells with specific measured characteristics for classification. Fluorescence flow cytometers were developed to improve cell analysis. In the late 1960’s, Van Dilla, Dittrich, and Göhde built fluorescence flow cytometers for reasons including measurement of DNA content and cell abnormalitites.
 * History: **

This technique was used in an article about gene silencing and Rheumatoid Arthritis. Flow cytometry was used to determine if IL-12 shRNA was effective in silencing IL-12. Dendritic cells were collected and stained, then labeled with an anti-IL-12 antibody. Analysis by flow cytometry revealed that IL-12 shRNA was able to silence IL-12 when compared to control shRNA. This data helps to provide evidence that IL-12shRNA transfected dendritic cells could be a therapeutic treatment for Rheumatoid Arthritis (Li, et. al 2012).
 * Application: **

Flow cytometry has been used in leukemia research. In a recent study, flow cytometry was used to measure the presence of monoclonal beta-cells subjects over 40 years with normal blood counts. Frequency of circulating peripheral blood monoclonal B-cells was higher than previously reported. This showed that sensitivity of the flow cytometry approach directly affects the observed frequency of PB clonal B-cells (Nieto, et. al 2009).

A third article reviews the use of flow cytometry for measurement of cellular markers in HIV disease. These markers include activation, differentiation, senescence, immune suppression, and function, which show the variable uses of flow cytometry. Flow cytometry has also been used to show changes in molecules involved in the pathogenesis of HIV over time. Measurement of these components by flow cytometry shows how important the technique has been in understanding the components of HIV, and different mechanisms involved (Chattopadhyay, Roederer, 2010).

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2008). //Molecular Biology of The Cell Fifth Edition.// New York: Garland Science, Taylor & Francis Group.
 * References: **

Chattopadhyay, P., & Roederer, M. (2010). Good cell, bad cell: Flow cytometry reveals T-Cell subsets important in HIV disease. //Cytometry//, 614-622.

Herzenberg, L., Parks, D., Sahaf, B., Perez, O., Roederer, M., & Herzenberg, L. (2002). The History and Future of the Fluorescence Activated Cell Sorter and Flow Cytometry: A View from Stanford. // Clinical Chemistry //, 1819-1827.

Li, R., et al. (2012). Gene Silencing of IL-12 in Dendritic Cells Inhibits Autoimmune Arthritis. //Journal of Translational Medicine//.

Nieto, W., et. al. (2009). Increased frequency (12%) of circulating chronic lymphotic leukemia-like B-cell clones in healthy subjects using a highly sensitive multicolor flow cytometry approach. //Blood//, 33-37.