Nearly 35 years since Stanford researcher Leonard Herzenberg and colleagues developed the first fluorescence activated cell sorter (FACS), the instrument has become the immunologists' key tool. Immunology journals are chock-full of flow-cytometry profiles, the characteristic plots that such instruments produce.
But cytometry is just half the story. The instruments also allow researchers to purify specific cell populations based on the presence or absence of particular characteristics. And therein lies their value. Using a FACS, a scientist can isolate and purify rare dendritic cells or hematopoietic stem cells from a patient's blood, for instance.
Herzenberg's prototypical FACS used a mercury arc light source and could measure just one parameter, fluorescence intensity. With monoclonal antibodies only just discovered, there were scant markers to study in any event. Data were archived by photographing an oscilloscope screen, and the instrument could process a mere 100,000 cells per minute.
Today's immunologists, in contrast, have access...