title: Modulation of spontaneous B-cell differentiation in macroglobulinemia by retinoic acid.
abstract: We previously showed that clonal blood B cells from patients with macroglobulinemia spontaneously differentiate in vitro to plasma cells. This process is dependent on an interleukin (IL)-6 autocrine pathway. We investigate here whether all-trans-retinoic acid (RA) interferes with B-cell differentiation either in patients with IgM gammapathy of undetermined significance (MGUS) or Waldenström's macroglobulinemia (WM). RA at a concentration of 10(-5) to 10(-8) mol/L inhibited by 50% to 80% the in vitro differentiation of purified B cells from four of five patients with MGUS and from one of five patients with WM as assessed by the IgM content of day 7 culture supernatants. We next determined whether this effect could be related to an inhibition of IL-6 secretion by cultured B cells and/or a downregulation of the IL-6 receptor (IL-6R), which was constitutively expressed on patients' blood B cells. A 50% to 100% (mean, 80%) inhibition of IL-6 production was found in seven of 10 patients (five with MGUS and two with WM). The IL-6R was no more detectable on cells from patients with MGUS after 2 days of treatment with RA and slightly downregulated in patients with WM. It was of interest that B cells susceptible to the action of RA belonged mostly to patients with IgM MGUS, which reinforces our previous data showing distinct requirements for IL-6-dependent differentiation of blood B cells from patients with VM or IgM MGUS.
authors.affiliation: Laboratory of Immunopathology, Hôpital Saint-Louis, Paris, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Levy
authors.forename: S
authors.initials: S
authors.lastname: Labaume
authors.forename: M C
authors.initials: MC
authors.lastname: Gendron
authors.forename: J C
authors.initials: JC
authors.lastname: Brouet
mesh_terms: D001402:B-Lymphocytes / Q000187:drug effects* / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D018123:Receptors, Interleukin / Q000032:analysis; D019947:Receptors, Interleukin-6; D014212:Tretinoin / Q000494:pharmacology*; D008258:Waldenstrom Macroglobulinemia / Q000097:blood*
chemical_list: D015850:Interleukin-6; D018123:Receptors, Interleukin; D019947:Receptors, Interleukin-6; D014212:Tretinoin