The experiment is called the “U937 experiment” after the U937 cell line. U937 cells are derived from a blood cancer and are easy to work with and produce reliable, strong intracellular signals.  ATCC refers to this cell line as CRL-1593.2 or U-937.

In this experiment, we measured phosphorylation of four signaling molecules: STAT1, STAT3, STAT5, and STAT6. These proteins are members of the signal transducers and activators of transcription (STAT) family, which convey intracellular signals as part of the JAK-STAT pathway. Phosphorylation of these proteins enables their dimerization, nuclear translocation, and transcriptional activity. 

We used 7 stimulation conditions: unstimulated cells and cells stimulated by interleukin 4 (IL-4), interferon gamma (IFNγ), granulocyte colony-stimulating factor (G-CSF), IFN Type I, IL-4 + IFNγ, and IL-6. These cytokines are powerful activators of specific STAT family proteins in U937 cells.

We abbreviate “phosphorylated STAT5” as “p-STAT5” and say this out loud as “phospho stat five” (not “p stat five”). The dash in “p-” (phospho) is used to distinguish this abbreviation from “p” (protein), which helps clarify text describing signaling of proteins such as p53 and p38 (e.g. p-p38, “phospho p 38”).  The signaling molecules were measured using two staining panels.  Panel 1 contained p-STAT6 conjugated to Alexa fluor 488 (Ax488), and p-STAT1 conjugated to Alexa 647 (Ax647).  Panel 2 contained p-STAT3 conjugated to Ax488 and p-STAT5 conjugated to Ax647.

During the analysis, we will identify a population of "live cells" by drawing a non-debris gate using forward and side scatter.  You can also refer to this population as "intact cells".