INTERACTION OF INTERLEUKIN-7 (IL-7) WITH GLYCOSAMINOGLYCANS AND ITS BIOLOGICAL RELEVANCE

We have investigated the binding of interleukin 7 (IL-7) to sulfated g lycosaminoglycans and evaluated its biological consequences. IL-7 bind s to heparin and heparan sulfate, to a lesser extent to dermatan sulfa te and does not bind to chondroitin sulfate. It was eluted from hepari n by 0.3-0.6 M NaCl and from heparan sulfate by <0.3 M NaCI. We also m easured the affinity of IL-7 for heparin using an affinity co-electrop horesis method and found an affinity of 25 nM. In spite of these findi ngs, IL-7 does not bind to the S17 cell line which supports lymphopoie sis. However, addition of heparin to cultures of an IL-7-dependent pre -B cell line (2E8) inhibited IL-7-stimulated proliferation and IL-7 co mplexed with heparin was more resistant than free IL-7 to protease tre atment. Taken together, these results suggest that heparin may act as a carrier for IL-7, blocking its interaction with target cells and pro tecting it from degradation during transit.