- A truncated isoform of the human beta chain common to the receptors for granulocyte-macrophage colony-stimulating factor, interleukin-3 (IL-3), and IL-5 with increased mRNA expression in some patients with acute leukemia. Gale, R.E., Freeburn, R.W., Khwaja, A., Chopra, R., Linch, D.C. Blood (1998)