Remove supernatant completely. Critical troubleshooting! This step is the primary cause of non-specific positive results with the secretion assay. Centrifuging cells into a pellet when they are still

warm will contaminate the assay. Keep the cells ice-cold to stop secretion Selleck Y27632 of cytokines after the secretion period. Ensure that the wash is in buffer, as the ethylenediamine tetraacetic acid (EDTA) helps to stop the reaction Repeat washing step in ice-cold buffer. During the second wash prepare the cytokine detection antibody. This is diluted by adding 20 µl of cytokine detection antibody stock to 80 µl of ice-cold buffer; 100 µl of this stock solution is required per 1 × 107 cells. For example, for 5 × 107 dilute 100 µl of reagent with 400 µl buffer. Store on ice until used. For detection of two cytokines, add 10 µl of each detection antibody per 80 µl buffer.

Critical step– if separating two cytokine populations consecutively, add only one anti-fluorochrome microbead at this point. The second microbead can be added after the first separation: repeat the steps described here. Completely remove supernate. Resuspend in 500 µl buffer. For magnetic labelling, add 100 µl diluted anti-PE or APC microbeads per 1 × 107 cells, mix well and incubate for 15 min at 8°C (i.e. in the refrigerator, not on ice). Critical step– it is essential to have an unseparated sample to work out the start frequency and subsequent recovery of cells. Prepare two MS columns per sample by rinsing LDK378 with 500 µl of cold buffer. Place the first column into the magnetic field of a suitable MACS Separator (e.g. MiniMACS). Troubleshooting – it is essential to use two columns. Each column

can enrich the cells about 100 times. Thus, because of the low frequency of cytokine-producing cells, two columns are required to obtain the best Bacterial neuraminidase purity. If cells are to be cultured: if cells are to be cultured directly after isolation, cells can also be eluted with culture medium. In this case, replace the last buffer wash with a medium wash, and then elute the cells with medium. If medium is to be used, ensure that it does not contain any particles, e.g. from serum. If in doubt, filter medium before use. If medium elution is used, cells for flow cytometry should be washed free of any phenol red. Critical point.  Do not use any PE- or APC-based tandem fluorochromes to stain cells sorted with anti-PE or APC beads, as they will be bound and stain non-specifically. All cytokine assays are low-frequency analyses. To properly identify cytokine producing cells, both positive staining with, e.g. CD4 or CD8 is required and also exclusion of unwanted cells from the analysis is vital. Exclusion of the dead cells (lymphocyte gating alone is not enough) using propridium iodide (PI), 7-AAD or other vital dyes will virtually eliminate non-specific background staining. It may also be necessary to exclude cells that tend to non-specifically bind fluorochromes, e.g.