The method can be used quite successfully to separate normal from abnormal cells in
bone marrow samples from patients with leukaemia. This can be used as a method of
cleaning the marrow prior to autologous(from the patient themselves) marrow
transplantation.
The technique is also used for diagnostic tests where the numbers of cell subtypes
need to be known. This is of particular use when looking at bloodborne cells such as
lymphocytes where the ratios of cell types can be of diagnostic significance. For
example, in HIV infection the numbers of specific T cell subtypes are of great
diagnostic significance in the progress of the infection toAIDS.
The cells are labelled with the antibodies to specific cell markers labelled with a
fluorescent label and then they are passed through a narrow gauge needle to produce an
aerosol. The droplet size is adjusted so that each one should contain only one cell. The
aerosol is then passed through a scanning Laser which allows detection of the fluores-
cent label. The droplets have a surface charge and can be deflected by an electron
magnet based on their fluorescent label status. The system relies on computer control to
effectively sort the cells into labelled and non-labelled populations. The desired cell
population can then be recovered and subsequently counted or cultured if desired. More
than one label can be used simultaneously so that multiple sorting can be undertaken.7.9 Cell and tissue staining techniques
There are many antibodies available that recognise receptors on and structural
proteins in cells and tissues and these can be of use diagnostically. Generally immuno-
staining is carried out on fixed tissues but this is not always the case as it may be
important to observe a dynamic event only seen in living cells. Different antibodiesReading laserElectromagnetic sorterSeparated cell
populationsCells passed through
aperture to create aerosolCells ( ) labelled with
fluorescent marker ( )
Fig. 7.17Fluorescent activated cell sorting.294 Immunochemical techniques