title: Modulation of the low-affinity IgE Fc receptor (Fc epsilon RII/CD23) by Leishmania chagasi.
abstract: Mature B lymphocytes and macrophages express low-affinity receptors for IgE (CD23 or Fc epsilon RII), a multifunctional molecule involved in IgE regulation, B cell growth and antigen presentation. We studied the effect of the protozoan Leishmania chagasi on CD23 expression using a model of early disease. Murine and human B cells, B cell lines, and a macrophage cell line incubated in vitro with the promastigote (PM) form of L. chagasi showed a selective loss of CD23 expression as detected by mAbs and IgE binding. Other B cell surface markers (class II MHC, CD32, surface IgM, surface IgD and gp90MEL-14) remained unchanged, indicating the loss was not due to B cell activation. The CD23 loss was parasite dose-dependent and required contact between PM and B cells. There was a loss of splenic B cell CD23 expression 24 h after infection of BALB/c mice with PM, indicating that the effect also occurred in vivo. During the activation of normal B cells, CD23 is cleaved by a cell-associated protease and released as a soluble form (sCD23). The human B cell line RPMI 8866 showed a 3- to 10-fold increase in the amount of sCD23 released into cultured supernatants when incubated with L. chagasi PM, which paralleled the loss of membrane-bound CD23 from the cell surface. In contrast, the steady-state level of CD23 mRNA did not change appreciably in RPMI 8866 cells during co-culture with PM. Thus, L. chagasi PM selectively down-modulated CD23 expression on B cells and macrophage cell lines, at least in part by increasing the release of sCD23.
authors.affiliation: Department of Pathology, University of Iowa College of Medicine, Iowa City 52242.
authors.forename: N N
authors.initials: NN
authors.lastname: Noben
authors.forename: M E
authors.initials: ME
authors.lastname: Wilson
authors.forename: R G
authors.initials: RG
authors.lastname: Lynch
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000469:parasitology; D002460:Cell Line; D002478:Cells, Cultured; D006224:Cricetinae; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis; D018314:Leishmania infantum / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000469:parasitology; D008647:Mesocricetus; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000096:biosynthesis; D017455:Receptors, IgE / Q000096:biosynthesis*; D013154:Spleen / Q000166:cytology / Q000469:parasitology
chemical_list: D012333:RNA, Messenger; D017455:Receptors, IgE; D007073:Immunoglobulin E