For immuno-detection see immuno-assays
In many applications it is desirable to enrich or alternatively deplete certain cell populations in a sample. Hematopoietic cells and immune cells have been separated on the basis of physical characteristics such as density. The advent of antibodies against cell surface antigens has also greatly expeanded the ability to distinguish and separate cell types. In positive selection techniques, the desired cells are labeled with antibodies and removed from the remaining unlabeled cells. In negative selection, the unwanted cells are labeled and removed. Discontinous density gradient centrifugation is commonly used to isolate peripheral blood mononuclear cells from ganulocytes and erythrocytes. Ficoll-Paque™ (Amersham Pharmacia Biotech) is one of the most popular desnity separation solutions used for this application. The blood is layered over Ficoll and then centrifuged. The erythroctyes, granulocytes and about 50% of the mononuclear cells settle to the cell pellet while the remaining 50% of mononuclear cells settle to the Ficoll plasma interace.
Positive/Negative Selection of B cells:
Viable B cells expressing antibody can be positively selected with a specificity to an antigen of interest by labelling the B cells with an anti-IgG antibody coupled to a fluorochrome and a viability dye. Positive staining can for example be done with a first label that stains IgG producing cells (e.g., FITC-anti-Rabbit Fc) and a second label that stains dead cells (e.g., PI or 7-AAD). (Allison, 14/776,945, US 2014/0287952).