Conversion of low-affinity interleukin 2 receptors to a high-affinity state following fusion of cell membranes.
The cellular receptors for interleukin 2 (IL-2) exist in at least two forms, one with a particularly high affinity and a second, more numerous class, with a much lower affinity for IL-2. Indirect evidence suggests that both classes of receptors use the same p55 glycoprotein as their ligand-binding component. L cells transfected with cDNA encoding this protein, however, displayed only low-affinity IL-2 binding. To determine if such receptors could be converted to a high-affinity state, L-cell membranes containing the murine p55 protein were fused with membranes from human T cells displaying high-affinity receptors. The anti-Tac antibody was used to block ligand binding to human p55 on the fusion product. The results showed that a fraction of the murine p55 chains were converted to a dramatically higher affinity following fusion. Fusion of the L-cell membranes with themselves or with membrane preparations from human T-cell lines lacking the IL-2 receptor resulted in little or no affinity modulation. One explanation of the results is that cofactors present in receptor-positive T-cell lines crossed species lines and combined with the murine p55 chain to create "high-affinity" binding sites. Thus, depending upon its environment, the same p55 molecule can apparently form either a low- or high-affinity IL-2 receptor.
D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000378:metabolism*; D007700:Kinetics; D008561:Membrane Fusion; D051379:Mice; D011971:Receptors, Immunologic / Q000378:metabolism*; D015375:Receptors, Interleukin-2
D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2