A standardized protocol for flow cytometric analysis of cells isolated from cerebrospinal fluid

Flow cytometry (FC) is an useful tool for the analysis of subpopulations in complex cell suspensions. When applying this method to the cerebrospinal fluid (CSF), some characteristic properties of this cell type must be taken into consideration: there are only few cells which decay rapidly in their native medium and during centrifugation. One aim of the immunostaining procedure preceding flow cytometric analysis must be to minimize cell loss in order to get an undistorted picture of 'true' CSF cell populations. Consequently, morphological flow cytometric plots of high resolution are an indispensable precondition for reliable determination of subpopulations defined by monoclonal antibody (Mab) binding. We describe a standardized protocol for the flow cytometric examination of CSF cells which minimizes undesired cell loss. By the use of a 'quality control' the extent of cell loss could be monitored. Examples of morphological flow cytometric plots are given. The subsequent determination of Mab binding subpopulations is critical when fluorescence intensities of antigen positive and negative cells are non-disjunct. A statistical test was developed for these cases often seen when cell surface determinants are expressed at low levels only.