Expression of the interleukin-2 receptor on human fibroblasts and its biological significance

Abstract

In this study, we have investigated the expression of the α and β chains of the IL-2 receptor (IL-2Rα, IL-2Rβ) both at the membrane and at transcrlptlonal levels during the lifespan of human embryonic fibroblasts. Here we show that the mAbs I0T14 and MIKβ1 directed against the IL-2 binding sites of the IL-2Rα and IL-2Rβ respectively, stain human embryonic fibroblasts early in their life span. Data from [¹²⁵l]rIL2 cross-linking experiments show the simultaneous expression of two IL-2 binding peptldes of 70 and 55 kDa respectively on embryonic young fibroblasts as on lymphold activated cells. The p55 and the p70 IL-2 binding peptides are shown to be specific for the IL-2Rα and to the IL-2Rβ by the finding that these bands are abolished by excess amounts of cold IL-2 and mAbs directed against the IL-2 binding sites of the α and β chains. Scatchard analysis after [¹²⁵I]IL-2 labelling shows the presence of both high affinity (150 sites with a K_d of 147 pM) and low affinity (1100 sites with a K_d of 4 nM) IL-2 binding sites. Northern blot and dot blot analysis show the presence of specific transcripts for the IL-2Rα and IL-2Rβ genes in early passaged fibroblasts. By contrast, In senescent cultures, only the IL-2Rβ transcript were detected. Finally, IL-2 at low concentrations (36 pM) down modulates the level of the intercellular adhesion molecule ICAM-1 in young but not in senescent cultures. Changes in the expression of the IL-2Rα during aging process probably affect the regulation of the ICAM-1 dependent flbroblastlc functions.