Encyclopedia of Medical Immunology

Living Edition
| Editors: Ian MacKay, Noel R. Rose

CD20 Deficiency, Lessons Related to Therapeutic Biologicals and Primary Immunodeficiency

  • Taco W. KuijpersEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-1-4614-9209-2_26-1


CD20 was one of the first B-cell-specific differentiation antigens identified (Stashenko et al. 1980). Nowadays, anti-CD20 immunotherapy using chimeric monoclonal antibodies (MoAbs) is used for the treatment of B-cell neoplasia, EBV-associated immunopathology, and a growing list of diseases with presumed autoimmune origin (Franks et al. 2016; Miano 2016; Claes et al. 2015; Froissart et al. 2015).

CD20, encoded by membrane-spanning 4 domains, subfamily a, member 1 (MS4A1; OMIM*112210), belongs to the MS4A family of molecules with multiple membrane-spanning domains (Liang et al. 2001; Liang and Tedder 2001) and is expressed on pre-B and mature B cells but is downregulated upon differentiation into plasma cells (Tedder and Engel 1994). CD20 is unlikely to have a natural ligand, but in vitro studies with CD20, MoAbs have demonstrated its involvement in the regulation of B-cell activation and proliferation (Tedder et al. 1985, 1986).

The CD20 gene structure and expression pattern are strongly conserved between mouse and human (Tedder et al. 1988, 1989; Uchida et al. 2004a), and CD20-knockout mice have been independently generated by two groups (Uchida et al. 2004a; O’Keefe et al. 1998). CD20–/– B cells develop and function normally, but spleen B cells exhibit demonstrable alterations in BCR- and CD19-induced Ca2+ responses (Uchida et al. 2004a). The importance of CD20 for the generation and function of human B cells has yet to be clarified.

B-Cell Development and Mechanistic Role for CD20

Peripheral B-cell survival relies on signals from the BCR and the BAFFR (O’Keefe et al. 1998). The BCR is a heterotrimeric complex consisting of Ag-binding Ig and the signaling Igα/Igβ heterodimers.

Crosslinking the BCR on mature B cells with Ag or anti-IgM Abs initiates multiple intracellular signaling cascades, which eventually lead to the activation of ERK, NF-kB, and NFAT pathways. Among these, NF-kB appears to play a prominently protective role in the survival of Ag-stimulated B cells by inducing the expression of several antiapoptotic proteins such as Bcl-2, Bcl-xL, and Bfl-1 (Mackay et al. 2010; Grumont et al. 1998, 1999). BCR signaling activates the canonical NF-kB pathway, which is characterized by the phosphorylation and ubiquitin-mediated degradation of IkB inhibitory proteins, in particular IkB-alpha. This leads to the translocation of NF-kB1 into the nucleus to activate target gene transcription. BAFFR is a member of the TNFR family.

Deficiency of BAFF or BAFFR results in an almost complete loss of follicular and marginal zone (MZ) B cells (Saijo et al. 2002; Schiemann et al. 2001; Thompson et al. 2001), demonstrating a critical role for BAFFR-mediated signaling in B-cell survival. In contrast to BCR, BAFFR activates the noncanonical NF-kB pathway, which depends on the proteolytic processing of p100 to p52 to generate p52/RelB (NF-kB2) nuclear complexes (Tedder et al. 1986, 1988, 1989; Uchida et al. 2004a; Claudio et al. 2002). Both BCR and BAFFR are required for the maintenance of peripheral B-cell homeostasis. It has been shown that signals from the BCR and BAFFR cooperate to allow B-cell survival at multiple stages of peripheral B-cell differentiation and during immune responses. BCR promotes BAFFR-mediated signals through at least two mechanisms by upregulating the expression of BAFFR and by supplying the noncanonical NF-kB pathway substrate p100 (Cancro 2009).

CD20 is a component of a multimeric cell surface complex that regulates Ca2+ transport across the plasma membrane (Bubien et al. 1993; Kanzaki et al. 1997). B-cell depletion using rituximab does not affect the CD19+CD20 pro-B cell and CD20CD138+ plasma cell populations, and within 6–8 months following treatment, the CD20+ B-cell compartment begins to replenish.

Although CD20 MoAb immunotherapy depletes normal and malignant B cells in vivo by antibody-dependent activation of the innate monocytic network (Uchida et al. 2004b), crosslinking of CD20 alters Ca2+ homeostasis, which influences cell cycle progression and can lead to apoptosis of normal and leukemic B cells in vitro (Bubien et al. 1993; van der Kolk et al. 2002). Yet the precise functions of CD20 and the therapeutic MoAbs are still controversial issues (Okroj et al. 2013).

Clinical Presentation, Differential Diagnosis, and Treatment

To date, only a single patient has been reported that completely lacked surface CD20 expression on B cells as a result of a homozygous mutation in the CD20 gene (Kuijpers et al. 2010). We found that the patient had a persistent hypogammaglobulinemia, normal B-cell numbers, and a strong reduction in circulating memory B cells. A decreased frequency of somatic hypermutations in IgG heavy chain genes was found. After repeated vaccinations the patient mounted proper responses to recall antigens but displayed a strongly reduced ability to respond to pneumococcal polysaccharides. In agreement with a conserved role of CD20 in the generation of T-cell-independent (TI) antibody responses, we found that CD20-deficient mice had a reduced ability to respond to TI antigens. We concluded that CD20 has a nonredundant role in the generation of optimal B-cell responses.

Human CD20 deficiency results in decreased IgG antibody levels and relatively increased IgM levels with weak responses against polysaccharides after vaccination. Importantly, we found that CD20 deficiency in mice also results in an impaired ability to make TI antibody responses. Thus, although the phenotypes of CD20-deficient humans and mice are subtly different, the current data would imply that CD20 signals are essential to enable B cells to optimally respond to antigenic stimuli.


The severe reduction of class-switched sIgDCD27+ memory B cells might reflect suboptimal germinal center formation and is likely to cause the profound hypogammaglobulinemia. Although IgG antibodies and circulating memory B cells are not defective in the CD20-knockout mice (Uchida et al. 2004a; O’Keefe et al. 1998), the selection of naive B cells into the non-switched (sIgD+CD27+) MZ B-cell compartment seems disturbed in the patient. In healthy donors, the transition of naive B cells into MZ B cells is accompanied by a reduction of the mean IgVH-CDR3 lengths and acquisition of IgV mutations (Tsuiji et al. 2006; Weller et al. 2004). Concomitantly, a counterselection against poly- and self-reactive antibodies and enrichment for antibodies reactive with specific bacterial polysaccharides occur (Tsuiji et al. 2006). This selection process is potentially driven by tonic BCR signals that may be assumed to be different between BCRs with longer and shorter IgVH-CDR3 lengths. Alternatively, particular self- or commensal-related antigens, recognized with low avidity, may provide positive BCR signals, favoring the selection of B cells that have short IgVH-CDR3 lengths in the MZ B cell compartment. In the MZ B cells of the patient, no counterselection for long IgVH-CDR3 lengths was observed, which is in accordance with a diminished response against polysaccharide vaccination. The notion of a disturbed counterselection against poly- and self-reactive antibodies is strengthened by the observation that, in the absence of any clinical signs of autoimmunity, antinuclear antibodies in the serum of the patient were found repeatedly (Kuijpers et al. 2010).

New Avenues to Approach CD20

Apart from cell-death-inducing capacity, murine anti-CD20 MoAbs were shown to also strongly inhibit IgM and IgG secretion by B cells in vitro (Golay et al. 1985). The first therapeutic anti-CD20 MoAb rituximab and new generation anti-CD20 MoAbs are, however, widely used now to treat autoimmune diseases and organ transplant rejection. Also in this case, the mechanism of action of rituximab is still unclear, as response does not simply correlate with B-cell depletion (Townsend et al. 2010). Thus, the data together suggest that in autoimmune diseases, anti-CD20 MoAbs may be therapeutically active through both killing the autoimmune B cells and inhibition of differentiation of the residual B cells into plasma cells secreting autoimmune antibodies. Experiments are required to verify this hypothesis and to determine whether all stimuli and all B-cell subsets may respond to such inhibition rather than cell death only.

Alternatively, low percentages of CD20-expressing T cells in human blood may be present with a pro-inflammatory role in autoimmunity as well. This minor T-cell subset was first described in 1993 (Hultin et al. 1993) and related to disease (Wilk et al. 2009), but the existence of this rather rare T-cell subset has also been disputed as an artifact (Henry et al. 2010). Others have found that CD20-expressing T cells can exhibit pro-inflammatory capacity. In rheumatoid arthritis (RA), CD20+ T cells make up a larger percentage of Th17 cells when compared with healthy individuals (Eggleton et al. 2011), although the overall percentage of CD20+ T cells among all T cells did not differ between RA patients and healthy individuals. Clearly, the pathological relevance, if any, of CD20+ T cells in autoimmune diseases remains unknown, but these findings give new impetus for the important avenue of investigation to understand the therapeutic effects of CD20 MoAbs – in particular in disease considered to be largely caused by T cells.


  1. Bubien JK, Zhou LJ, Bell PD, Frizzell RA, Tedder TF.Transfection of the CD20 cell surface molecule into ectopic cell types generates a Ca2+ conductance found constitutively in B lymphocytes. J Cell Biol. 1993;121(5):1121–32.CrossRefGoogle Scholar
  2. Cancro MP. Signalling crosstalk in B cells: managing worth and need. Nat Rev Immunol. 2009;9:657–61.CrossRefGoogle Scholar
  3. Claes N, Fraussen J, Stinissen P, Hupperts R, Somers V. B cells are multifunctional players in multiple sclerosis pathogenesis: insights from therapeutic interventions. Front Immunol. 2015;6:642.CrossRefGoogle Scholar
  4. Claudio E, Brown K, Park S, Wang H, Siebenlist U. BAFF-induced NEMO-independent processing of NF-kB2 in maturing B cells. Nat Immunol. 2002;3:958–65.CrossRefGoogle Scholar
  5. Eggleton P, Bremer E, Tarr JM, de Bruyn M, Helfrich W, Kendall A, Haigh RC, Viner NJ, Winyard PG. Frequency of Th17 CD20+ cells in the peripheral blood of rheumatoid arthritis patients is higher compared to healthy subjects. Arthritis Res Ther. 2011;13:R208.CrossRefGoogle Scholar
  6. Franks SE, Getahun A, Hogarth PM, Cambier JC. Targeting B cells in treatment of autoimmunity. Curr Opin Immunol. 2016;43:39–45.CrossRefGoogle Scholar
  7. Froissart A, Veyradier A, Hié M, Benhamou Y, Coppo P, French Reference Center for Thrombotic Microangiopathies. Rituximab in autoimmune thrombotic thrombocytopenic purpura: a success story. Eur J Intern Med. 2015;26(9):659–65.CrossRefGoogle Scholar
  8. Golay JT, Clark EA, Beverley PC. The CD20 (Bp35) antigen is involved in activation of B cells from the G0 to the G1 phase of the cell cycle. J Immunol. 1985;135:3795–801.PubMedGoogle Scholar
  9. Grumont RJ, Rourke IJ, O’Reilly LA, Strasser A, Miyake K, Sha W, Gerondakis S. B lymphocytes differentially use the Rel and nuclear factor kB1 (NF-kB1) transcription factors to regulate cell cycle progression and apoptosis in quiescent and mitogen-activated cells. J Exp Med. 1998;187:663–74.CrossRefGoogle Scholar
  10. Grumont RJ, Rourke IJ, Gerondakis S. Rel-dependent induction of A1 transcription is required to protect B cells from antigen receptor ligation-induced apoptosis. Genes Dev. 1999;13:400–11.CrossRefGoogle Scholar
  11. Henry C, Ramadan A, Montcuquet N, Pallandre JR, Mercier-Letondal P, Deschamps M, Tiberghien P, Ferrand C, Robinet E. CD3+CD20+ cells may be an artifact of flow cytometry: comment on the article by Wilk et al. Arthritis Rheum. 2010;62:2561–3. (author reply 2563–2565)CrossRefGoogle Scholar
  12. Hultin LE, Hausner MA, Hultin PM, Giorgi JV. CD20 (pan-B cell) antigen is expressed at a low level on a subpopulation of human T lymphocytes. Cytometry. 1993;14:196–204.CrossRefGoogle Scholar
  13. Kanzaki M, Lindorfer MA, Garrison JC, Kojima I. Activation of the calcium-permeable cation channel CD20 by alpha subunits of the Gi protein. J Biol Chem. 1997;272(23):14733–9.CrossRefGoogle Scholar
  14. Kuijpers TW, Bende RJ, Baars PA, Grummels A, Derks IA, Dolman KM, Beaumont T, Tedder TF, van Noesel CJ, Eldering E, van Lier RA. CD20 deficiency in humans results in impaired T cell-independent antibody responses. J Clin Invest. 2010;120:214–22.CrossRefGoogle Scholar
  15. Liang Y, Tedder TF. Identification of a CD20-, FcepsilonRIbeta-, and HTm4-related gene family: sixteen new MS4A family members expressed in human and mouse. Genomics. 2001;72(2):119–27.CrossRefGoogle Scholar
  16. Liang Y, Buckley TR, Tu L, Langdon SD, Tedder TF. Structural organization of the human MS4A gene cluster on Chromosome 11q12. Immunogenetics. 2001;53(5):357–68.CrossRefGoogle Scholar
  17. Mackay F, Figgett WA, Saulep D, Lepage M, Hibbs ML. B-cell stage and context-dependent requirements for survival signals from BAFF and the B-cell receptor. Immunol Rev. 2010;237:205–25.CrossRefGoogle Scholar
  18. Miano M. How I manage Evans syndrome and AIHA cases in children. Br J Haematol. 2016;172(4):524–34.CrossRefGoogle Scholar
  19. O’Keefe TL, Williams GT, Davies SL, Neuberger MS. Mice carrying a CD20 gene disruption. Immunogenetics. 1998;48(2):125–32.CrossRefGoogle Scholar
  20. Okroj M, Osterborg A, Blom AM. Effector mechanisms of anti-CD20 monoclonal antibodies in B cell malignancies. Cancer Treat Rev. 2013;39:632–6.CrossRefGoogle Scholar
  21. Saijo K, Mecklenbrauker I, Santana A, Leitger M, Schmedt C, Tarakhovsky A. Protein kinase C beta controls nuclear factor kB activation in B cells through selective regulation of the IkB kinase alpha. J Exp Med. 2002;195:1647–52.CrossRefGoogle Scholar
  22. Schiemann B, Gommerman JL, Vora K, Cachero TG, Shulga-Morskaya S, Dobles M, Frew E, Scott ML. An essential role for BAFF in the normal development of B cells through a BCMA-independent pathway. Science. 2001;293:2111–4.CrossRefGoogle Scholar
  23. Stashenko P, Nadler LM, Hardy R, Schlossman SF. Characterization of a human B lymphocyte-specific antigen. J Immunol. 1980;125(4):1678–85.PubMedGoogle Scholar
  24. Tedder TF, Engel P. CD20: a regulator of cell-cycle progression of B lymphocytes. Immunol Today. 1994;15(9):450–4.CrossRefGoogle Scholar
  25. Tedder TF, et al. The B cell surface molecule B1 is functionally linked with B cell activation and differentiation. J Immunol. 1985;135(2):973–9.PubMedGoogle Scholar
  26. Tedder TF, et al. Antibodies reactive with the B1 molecule inhibit cell cycle progression but not activation of human B lymphocytes. Eur J Immunol. 1986;16(8):881–7.CrossRefGoogle Scholar
  27. Tedder TF, et al. Cloning of a complementary DNA encoding a new mouse B lymphocyte differentiation antigen, homologous to the human B1 (CD20) antigen, and localization of the gene to chromosome 19. J Immunol. 1988;141(12):4388–94.PubMedGoogle Scholar
  28. Tedder TF, Klejman G, Schlossman SF, Saito H. Structure of the gene encoding the human B lymphocyte differentiation antigen CD20 (B1). J Immunol. 1989;142(7):2560–8.PubMedGoogle Scholar
  29. Thompson JS, Bixler SA, Qian F, Vora K, Scott ML, Cachero TG, Hession C, Schneider P, Sizing ID, Mullen C, et al. BAFF-R, a newly identified TNF receptor that specifically interacts with BAFF. Science. 2001;293:2108–11.CrossRefGoogle Scholar
  30. Townsend MJ, Monroe JG, Chan AC. B-cell targeted therapies in human autoimmune diseases: an updated perspective. Immunol Rev. 2010;237:264–83.CrossRefGoogle Scholar
  31. Tsuiji M, et al. A checkpoint for autoreactivity in human IgM+ memory B cell development. J Exp Med. 2006;203(2):393–400.CrossRefGoogle Scholar
  32. Uchida J, Lee Y, Hasegawa M, Liang Y, Bradney A, Oliver JA, Bowen K, Steeber DA, Haas KM, Poe JC, Tedder TF. Mouse CD20 expression and function. Int Immunol. 2004a;16:119–29.CrossRefGoogle Scholar
  33. Uchida J, et al. The innate mononuclear phagocyte network depletes B lymphocytes through Fc receptor-dependent mechanisms during anti-CD20 antibody immunotherapy. J Exp Med. 2004b;199(12):1659–69.CrossRefGoogle Scholar
  34. van der Kolk LE, et al. CD20-induced B cell death can bypass mitochondria and caspase activation. Leukemia. 2002;16(9):1735–44.CrossRefGoogle Scholar
  35. Weller S, et al. Human blood IgM “memory” B cells are circulating splenic marginal zone B cells harboring a prediversified immunoglobulin repertoire. Blood. 2004;104(12):3647–54.CrossRefGoogle Scholar
  36. Wilk E, Witte T, Marquardt N, Horvath T, Kalippke K, Scholz K, Wilke N, Schmidt RE, Jacobs R. Depletion of functionally active CD20+ T cells by rituximab treatment. Arthritis Rheum. 2009;60:3563–71.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Pediatric Hematology, Immunology and Infectious DiseasesAcademic Medical Center (AMC), Emma Children’s HospitalAmsterdamThe Netherlands

Section editors and affiliations

  • Klaus Warnatz
    • 1
  • Joris M. van Montfrans
    • 2
  1. 1.Center for Chronic ImmunodeficiencyUniversity Medical Center and University of FreiburgFreiburgGermany
  2. 2.UMC UtrechtUtrechtNetherlands