Study of the B cell memory compartment in common variable immunodeficiency

109

Common variable immune deficiency (CVID) is a primary immune deficiency characterized by low levels of serum immune globulins, lack of Ab, and reduced numbers of CD27+ memory B cells. Although T, B, and dendritic cell defects have been described, for the great majority, genetic causes have not been identified. In these experiments, we investigated B cell and plasmacytoid dendritic cell activation induced via TLR9, an intracellular recognition receptor that detects DNA-containing CpG motifs from viruses and bacteria. CpG-DNA activates normal B cells by the constitutively expressed TLR9, resulting in cytokine secretion, IgG class switch, immune globulin production, and potentially, the preservation of long-lived memory B cells. We found that CpG-DNA did not up-regulate expression of CD86 on CVID B cells, even when costimulated by the BCR, or induce production of IL-6 or IL-10 as it does for normal B cells. TLR9, found intracytoplasmically and on the surface of oligodeoxynucleotide-activated normal B cells, was deficient in CVID B cells, as was TLR9 mRNA. TLR9 B cell defects were not related to proportions of CD27+ memory B cells. CpG-activated CVID plasmacytoid dendritic cells did not produce IFN-α in normal amounts, even though these cells contained abundant intracytoplasmic TLR9. No mutations or polymorphisms of TLR9 were found. These data show that there are broad TLR9 activation defects in CVID which would prevent CpG-DNA-initiated innate immune responses; these defects may lead to impaired responses of plasmacytoid dendritic cells and loss of B cell function.

Section: Discussionmentioning

confidence: 99%

TLR9 Activation Is Defective in Common Variable Immune Deficiency

Cunningham‐Rundles

Radigan

Knight

et al. 2006

109

“…Although various abnormalities in number and function of T cells (3)(4)(5)(6)(7), B cells (8)(9)(10)(11)(12)(13), and dendritic cells (14)(15)(16) have been described, the immunopathological mechanism leading to disturbed Ab production in CVID patients has not yet been defined.…”

Section: Ommon Variable Immunodeficiency (Cvid) Is a Clinically Hetmentioning

confidence: 99%

Characterization of Lymphocyte Subsets in Patients with Common Variable Immunodeficiency Reveals Subsets of Naive Human B Cells Marked by CD24 Expression

Vlková

Froňková

Kanderová

et al. 2010

Increased proportions of naive B cell subset and B cells defined as CD27negCD21negCD38neg are frequently found in patients with common variable immunodeficiency (CVID) syndrome. Current methods of polychromatic flow cytometry and PCR-based detection of κ deletion excision circles allow for fine definitions and replication history mapping of infrequent B cell subsets. We have analyzed B cells from 48 patients with CVID and 49 healthy controls to examine phenotype, frequency, and proliferation history of naive B cell subsets. Consistent with previous studies, we have described two groups of patients with normal (CVID-21norm) or increased (CVID-21lo) proportions of CD27negCD21negCD38neg B cells. Upon further analyses, we found two discrete subpopulations of this subset based on the expression of CD24. The B cell subsets showed a markedly increased proliferation in CVID-21lo patients as compared with healthy controls, suggesting developmental arrest rather than increased bone marrow output. Furthermore, when we analyzed CD21pos naive B cells, we found two different subpopulations based on IgM and CD24 expression. They correspond to follicular (FO) I and FO II cells previously described in mice. FO I subset is significantly underrepresented in CVID-21lo patients. A comparison of the replication history of naive B cell subsets in CVID patients and healthy controls implies refined naive B cell developmental scheme, in which human transitional B cells develop into FO II and FO I. We propose that the CD27negCD21negCD38neg B cells increased in some of the CVID patients originate from the two FO subsets after loss of CD21 expression.

“…In addition to XLP, several other conditions are characterized by a deficiency of memory B cells and hypogammaglobulinemia, including CVID (20,22,43) and post-HSCT (25,44). Humoral immune responses are also reduced in neonates (45).…”

Section: Transitional B Cells Are Expanded In Humoral Immunodeficiencmentioning

confidence: 99%

Expansion of Functionally Immature Transitional B Cells Is Associated with Human-Immunodeficient States Characterized by Impaired Humoral Immunity

Cuss

Avery

Cannons

et al. 2006

177

188

X-linked lymphoproliferative disease (XLP) is a severe immunodeficiency associated with a marked reduction in circulating memory B cells. Our investigation of the B cell compartment of XLP patients revealed an increase in the frequency of a population of B cells distinct from those previously defined. This population displayed increased expression of CD10, CD24, and CD38, indicating that it could consist of circulating immature/transitional B cells. Supporting this possibility, CD10+CD24highCD38high B cells displayed other immature characteristics, including unmutated Ig V genes and elevated levels of surface IgM; they also lacked expression of Bcl-2 and a panel of activation molecules. The capacity of CD24highCD38high B cells to proliferate, secrete Ig, and migrate in vitro was greatly reduced compared with mature B cell populations. Moreover, CD24highCD38high B cells were increased in the peripheral blood of neonates, patients with common variable immunodeficiency, and patients recovering from hemopoietic stem cell transplant. Thus, an expansion of functionally immature B cells may contribute to the humoral immunodeficient state that is characteristic of neonates, as well as patients with XLP or common variable immunodeficiency, and those recovering from a stem cell transplant. Further investigation of transitional B cells will improve our understanding of human B cell development and how alterations to this process may precipitate immunodeficiency or autoimmunity.