CD20 deficiency in humans results in impaired T cell–independent antibody responses
Taco W. Kuijpers, Richard J. Bende, Paul A. Baars, Annette Grummels, Ingrid A.M. Derks, Koert M. Dolman, Tim Beaumont, Thomas F. Tedder, Carel J.M. van Noesel, Eric Eldering, René A.W. van Lier
Taco W. Kuijpers, Richard J. Bende, Paul A. Baars, Annette Grummels, Ingrid A.M. Derks, Koert M. Dolman, Tim Beaumont, Thomas F. Tedder, Carel J.M. van Noesel, Eric Eldering, René A.W. van Lier
View: Text | PDF
Research Article Immunology

CD20 deficiency in humans results in impaired T cell–independent antibody responses

Abstract

CD20 was the first B cell differentiation antigen identified, and CD20-specific mAbs are commonly used for the treatment of B cell malignancies and autoantibody-mediated autoimmune diseases. Despite this the role of CD20 in human B cell physiology has remained elusive. We describe here a juvenile patient with CD20 deficiency due to a homozygous mutation in a splice junction of the CD20 gene (also known as MS4A1) that results in “cryptic” splicing and nonfunctional mRNA species. Analysis of this patient has led us to conclude that CD20 has a central role in the generation of T cell–independent (TI) antibody responses. Key evidence to support this conclusion was provided by the observation that although antigen-independent B cells developed normally in the absence of CD20 expression, antibody formation, particularly after vaccination with TI antigens, was strongly impaired in the patient. Consistent with this, TI antipolysaccharide B cell responses were severely impeded in CD20-deficient mice. Our study therefore identifies what we believe to be a novel type of humoral immunodeficiency caused by CD20 deficiency and characterized by normal development of antigen-independent B cells, along with a reduced capacity to mount proper antibody responses.

Authors

Taco W. Kuijpers, Richard J. Bende, Paul A. Baars, Annette Grummels, Ingrid A.M. Derks, Koert M. Dolman, Tim Beaumont, Thomas F. Tedder, Carel J.M. van Noesel, Eric Eldering, René A.W. van Lier

×

Figure 3

B cell function in vitro.

Options: View larger image (or click on image) Download as PowerPoint
B cell function in vitro. (A) Cells lacking CD20 respond to IgG and IgM ...
(A) Cells lacking CD20 respond to IgG and IgM BCR stimulation by Ca2+ flux. B cell lines from donors expressing wild-type, intermediate, or no CD20 were cultured for 4 hours without CD40L in the presence of IL-21 before being loaded with Indo-1 AM. Cells were maintained at room temperature and incubated with a control and subsequently with anti-BCR mAbs. Fluorescence ratios of Indo-1 emission at 405/485 nm were measured by flow cytometry. Ca2+ flux curves were adjusted graphically to the same starting level fluorescence 4/fluorescence 5(FL4/FL5) ratio, and the starting point of the stimulus was set at the same time point. In general, all cells responded to BCR stimulation by showing intracellular Ca2+ fluxes. (B) CFSE-labeled PBMCs were stimulated with indicated stimuli for 6 days, and CD19+CD20+ B cells were analyzed by flow cytometry for CFSE dilution. The percentage of dividing B cells (precursor frequencies) was calculated. Supernatants were tested by ELISA for IgM and IgG secretion. NT, not tested due to stimulus. Values represent mean ± SEM and are obtained for 3–4 healthy donors.