Interleukin-2 (IL-2) receptor α, β and γ subunit expression as a function of B-cell lineage ontogeny: The use of IL-2-PE66(4Glu) to characterize internalization via IL-2 receptor subunits

Interleukin-2 (IL-2) is a pluripotent cytokine which plays a crucial role in the immune system response. Although the IL-2/IL-2 receptor (IL-2R) system has been well characterized in cells of the T lineage it is less known in B lymphocytes. The authors therefore studied the expression of the 1L- 2Rα, β and γ subunits in human B-cell lines at different stages of maturation, by the polymerase chain reaction technique. The authors found that the α and β subunits are expressed in the final stages of B-cell lineage maturation, whereas the γ subunit is constitutively expressed during B-lymphocyte differentiation. The results indicate that the IL-2/IL-2R system, most probably, does not have a role in the early stages of B-cell differentiation, but may be involved only in the final stages of B-cell lineage ontogeny. Moreover, the ability of the different forms of IL-2R to internalize the IL-2 ligand was investigated, using the chimeric protein IL- 2-PE66(4GLU). Cell lines bearing the αγ, βγ and αβγ forms of IL-2R were inhibited by the chimeric protein, while those bearing the γ subunit alone did not respond to the chimera. Thus, internalization of IL-2 is most likely mediated via the αγ form of the IL-2R, as shown here for the first time, as well as through the βγ, and αβγ IL-2R forms. However, IL-2 cannot be internalized through the IL-2R γ subunit alone.