Flow cytometry

Flow cytometry
-----------------------
• Flow cytometry measures multiple characteristics of individual particles flowing in single file in a stream of fluid.
• It provides rapid analysis of multiple characteristics of single cells.
• It can measure following characteristics:
a) Cell size
b) Cytoplasmic complexity
c) DNA or RNA content
d) Wide range of membrane-bound and intracellular proteins.
• Flow cytometry measures optical and fluorescence characteristics of single cells.
• Principle of flow cytometry:
It measure fluorescence intensity produced by fluorescent-labelled antibodies detecting proteins or ligands that bind to specific cell-associated molecules, such as DNA binding by propidium iodide. 
• The direction of light scattered by the cell correlates to: 
a) Forward Scatter (FS) for Cell size.
b) Side Scatter (SS) for density of the cell (Granularity, vacuoles and membrane size).
• Live cells will have more forward scatter(FS) than dead and apoptotic cells.
• Granulocytes or monocytes have more granularity or vacuoles and they will have more side scattering (SS).

• Clinical uses of flow cytometry:
a) Immunology
1) Histocompatibility cross-matching 
2) Transplantation rejection
3) Immunodeficiency studies
4) HLA-B27 detection
5) Lymphocytosis

b) Oncology 
1) DNA content and S phase of tumors 
2) Measurement of proliferation markers e.g. Ki-67.
c) Leukemia and lymphoma phenotyping
d) Reticulocyte enumeration

Courtesy : Devesh Mishra