An interleukin receptor subunit that was originally discovered as a component of the $INTERLEUKIN-$2 RECEPTOR. It was subsequently found to be a component of several other receptors including the $INTERLEUKIN-$4 RECEPTOR, the $INTERLEUKIN-$7 RECEPTOR, the $INTERLEUKIN-$9 RECEPTOR, the $INTERLEUKIN-$15 RECEPTOR, and the $INTERLEUKIN-$21 RECEPTOR. Mutations in the gene for the interleukin common gamma chain have been associated with X-LINKED COMBINED IMMUNODEFICIENCY DISEASES.