Genetic CD21 deficiency is associated with hypogammaglobulinemia

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• 作者：Jens Thiel ; MD^a ; ^b ; ^&lowast ; ; ^{jens.thiel@uniklinik-freiburg.de} ; Lucas Kimmig ; MD^a ; ^&lowast ; ; Ulrich Salzer ; MD^a ; ^b ; ^&lowast ; ; Magdalena Grudzien ; PhD^a ; Dirk Lebrecht ; PhD^a ; Tina Hagena^a ; Ruth Draeger^a ; Nadine Vö ; lxen ; MSc^a ; ^b ; Astrid Bergbreiter ; MSc^a ; ^b ; Stephanie Jennings ; PhD^a ; ^b ; Sylvia Gutenberger^a ; ^b ; Annette Aichem ; PhD^c ; Harald Illges ; PhD^d ; Jonathan P. Hannan ; PhD^e ; Anne-Kathrin Kienzler ; MSc^a ; ^b ; ^f ; Marta Rizzi ; MD ; PhD^a ; ^b ; ^f ; Hermann Eibel ; PhD^a ; ^b ; ^f ; Hans-Hartmut Peter ; MD^a ; ^b ; Klaus Warnatz ; MD^a ; ^b ; Bodo Grimbacher ; MD^a ; ^g ; Jö ; rg-Andres Rump ; MD^a ; ^&Dagger ; ; Michael Schlesier ; PhD^a ; ^b ; ^&Dagger ;
• 关键词：CD21 ; complement receptor ; hypogammaglobulinemia ; common variable immunodeficiency ; B lymphocyte
• 刊名：Journal of Allergy and Clinical Immunology
• 出版年：2012
• 出版时间：March, 2012
• 年：2012
• 卷：129
• 期：3
• 页码：801-810.e6
• 全文大小：1514 K

文摘

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Background

Complement receptor 2 (CR2/CD21) is part of the B-cell coreceptor and expressed by mature B cells and follicular dendritic cells. CD21 is a receptor for C3d-opsonized immune complexes and enhances antigen-specific B-cell responses.

Objective

Genetic inactivation of the murine CR2 locus results in impaired humoral immune responses. Here we report the first case of a genetic CD21 deficiency in human subjects.

Methods

CD21 protein expression was analyzed by means of flow cytometry and Western blotting. CD21 transcripts were quantified by using real-time PCR. The CD21 gene was sequenced. Wild-type and mutant CD21 cDNA expression was studied after transfection of 293T cells. Binding of EBV-gp350 or C3d-containing immune complexes and induction of calcium flux in CD21-deficient B cells were analyzed by means of flow cytometry. Antibody responses to protein and polysaccharide vaccines were measured.

Results

A 28-year-old man presented with recurrent infections, reduced class-switched memory B cells, and hypogammaglobulinemia. CD21 receptor expression was undetectable. Binding of C3d-containing immune complexes and EBV-gp350 to B cells was severely reduced. Sequence analysis revealed a compound heterozygous deleterious mutation in the CD21 gene. Functional studies with anti-immunoglobulin- and C3d-containing immune complexes showed a complete loss of costimulatory activity of C3d in enhancing suboptimal B-cell receptor stimulation. Vaccination responses to protein antigens were normal, but the response to pneumococcal polysaccharide vaccination was moderately impaired.

Conclusions

Genetic CD21 deficiency adds to the molecular defects observed in human subjects with hypogammaglobulinemia.