title: Novel receptor-mediated internalization of interleukin 2 in B cells.
abstract: Novel IL-2-binding molecules (p70 and p75) mediating internalization and degradation of IL-2 were examined by employing a human B lymphoblastoid line, SKW6-4 cells. High concentrations of IL-2 induced IgM secretion in these cells through a receptor distinct from Tac antigen. The acid-wash technique revealed that more than 60% of 125I-labeled IL-2 bound to the cells became acid-unremovable in the first 30 min of incubation at 37 degrees C and degradation products of 125I-IL-2 increased after 30 min of incubation. Treatment of the cells with NaN3 buffer inhibited the appearance of acid-unremovable 125I-IL-2, suggesting that acid-unremovable 125I-IL-2 was not due to fluid-phase pinocytosis but due to internalization. Loss of labeled bands by incubation of cells with 125I-IL-2 at 37 degrees C before affinity cross-linking demonstrated that 125I-IL-2 was internalized via novel IL-2-binding molecules. These results suggest that novel IL-2-binding molecules are responsible for internalization and may mediate signal transduction in B cells in the absence of Tac antigen.
mesh_terms: D001386:Azides / Q000494:pharmacology; D001402:B-Lymphocytes / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D003432:Cross-Linking Reagents; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis; D007376:Interleukin-2 / Q000378:metabolism* / Q000494:pharmacology; D010873:Pinocytosis; D011971:Receptors, Immunologic / Q000302:isolation & purification / Q000502:physiology*; D015375:Receptors, Interleukin-2; D019810:Sodium Azide
chemical_list: D001386:Azides; D003432:Cross-Linking Reagents; D007075:Immunoglobulin M; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D019810:Sodium Azide