Cells In Common Variable Immunodeficiency Research Articles

Expansion of CD19 hiCD21 lo/neg B Cells in Common Variable Immunodeficiency (CVID) Patients with Autoimmune Cytopenia

Common variable immunodeficiency (CVID) is characterized by a severe hypogammaglobulinemia. While the clinical picture is dominated by recurrent respiratory and gastrointestinal infections, a subgroup of up to 30% of the patients develops additional autoimmune phenomena, including thrombocytopenia and autoimmune hemolytic anemia. So far no classification allowed a prediction of the coincidence of immunodeficiency and autoimmunity. Here, we propose the size of the peripheral CD19(hi)CD2(lo/neg) B cell pool as a marker for CVID patients with autoimmune cytopenia and splenomegaly. Interestingly similar B cell populations are also found in patients with SLE and may not only be an epiphenomenon of the disease.

Enhanced apoptosis of T cells in common variable immunodeficiency (CVID): role of defective CD28 co-stimulation

CVID is a primary immune disorder in which hypogammaglobulinaemia may be associated with a number of T cell defects including lymphopenia, anergy, impaired lymphocyte proliferation and deficient cytokine secretion. In this study we show that T cells of CVID subjects, in comparison with control T cells, undergo spontaneous apoptosis in culture and markedly accelerated apoptosis after gamma-irradiation. Although costimulation of the CD28 receptor following engagement of the TCR/CD3 receptor normally provides a second signal necessary for IL-2 secretion, CD28 costimulation in CVID does not significantly increase IL-2 production, nor does this combination of activators enhance the survival of irradiated CVID T cells, as it does for cultured normal T cells. Addition of IL-2 enhances CVID T cell survival, suggesting that the IL-2 signalling pathways are normal. CVID T cells have similar expression of Bcl-2 to control T cells. CD3 stimulation up-regulates T cell expression of bcl-xL mRNA for normal T cells, but anti-CD28 does not augment bcl-xL expression for CVID subjects with accelerated apoptosis. Defects of the CD28 receptor pathway, leading to cytokine deprivation and dysregulation of bcl-xL, could lead to poor T cell viability and some of the cellular defects observed in CVID.

Deficiency in circulating natural killer (NK) cell subsets in common variable immunodeficiency and X-linked agammaglobulinaemia.

Absolute and relative NK cell numbers were determined in peripheral whole blood by flow cytometry in patients with common variable immunodeficiency (CVID) (n = 55) and X-linked agammaglobulinaemia (XLA) (n = 19) on regular immunoglobulin (IVIG) therapy. Absolute CD3-CD16+ NK cell numbers were significantly reduced in CVID patients (median 108/microl, range 23-815), compared with normal subjects (n = 60) (289/microl, range 56-640, P < 0.001). Total lymphocyte concentrations were significantly lower in CVID (median 1587/microl, range 523-7519) compared with normal subjects (median 2019/microl, range 1124-3149, P = 0.004), with the percentage of NK cells also being significantly decreased (median 7.5%, range 3.0-33. 0%, compared with 14.2%, range 2.6-30.8%, P < 0.001). In XLA, absolute NK cell numbers (median 140/microl, range 32-551, P < 0. 001) but not relative numbers were significantly reduced compared with normal controls. We excluded the possibility that IVIG interferes with in vitro binding of CD16 MoAbs. Further analysis of NK cell subsets showed a deficiency of both CD16+ and CD56+ cells in CVID, most marked in the CD3-CD8dim subpopulation, which may be due to increased homing of these cells to the gut. Serial studies on a small number of patients suggest that IVIG therapy has no short-term effect on NK cells, although we cannot exclude an effect with prolonged use. Although there are no obvious clinical effects of the NK depletion in CVID and XLA, this may be a factor in their predisposition to cancer.

Failure of B cells in common variable immunodeficiency to transit from proliferation to differentiation is associated with altered B cell surface-molecule display

B cells from patients with common variable immunodeficiency (CVI) were investigated as to their surface-molecule display and their functional ability to transit through defined in vitro developmental stages. Patients' B cells were analyzed by dual color-flow cytometry and found to have an abnormal surface-molecule display characterized by depressed Leu 8 and CD21 expression. Membrane immunoglobulin (mu, delta, and light chain) were normally displayed. The lack of Leu 8 and CD21 expression did not represent the normal loss of these antigens from B cells with activation because the cells did not demonstrate enhanced display of activation markers, nor did they demonstrate enhanced display of early B cell molecules, such as common acute lymphocytic leukemia antigen or CD5. Small resting B cells from the patients were isolated and tested for their ability to respond functionally to a series of activation, proliferation, and differentiation signals. B cells from 14 of 17 patients failed to transit from proliferation to differentiation with increased immunoglobulin production when B cells were stimulated with T cell replacing factor ± phorbol myristate acetate. Cells of one patient failed to proliferate, whereas B cells from the remaining two patients with CVI did not undergo activation (size change and RNA synthesis) when they were exposed to antimu antibody or low-dose phorbol myristate acetate. These studies demonstrate that most patients with CVI have B cells displaying an altered-surface phenotype that is associated with a specific functional defect in transiting from cell proliferation to differentiation and immunoglobulin production.

Analysis of B cell dysfunction in patients with common variable immunodeficiency by using recombinant interleukin 2.

Recombinant interleukin 2 (RIL2) induces proliferation and differentiation of the Staphylococcus aureus Cowan I (SAC)-activated normal B cells to immunoglobulin (Ig) producting cells. We applied this finding to an analysis of heterogeneity in the differentiation states of B cells in patients with common variable immunodeficiency (CVI). B cells from 5 of 7 patients with CVI were tested for their ability to proliferate under the stimulation of SAC, or SAC and RIL2, and for their differentiation to Ig producing cells in the presence of SAC plus RIL2. The results suggest that the differentiation status of B cells in CVI could be divided into four states based on their responses to SAC and RIL2. In the first state, no B cell proliferation or differentiation was demonstrated in our assays. B cells in the second state showed normal proliferative responses to SAC, but not to SAC plus RIL2, and no differentiation to Ig-secreting cells. The third state showed normal proliferation in response to SAC and SAC plus RIL2, but no differentiation to Ig-secreting cells. The fourth state had a normal proliferation response to SAC and SAC plus RIL2, and normal secretions of IgG and IgM in response to SAC and RIL2. These results show that some B cells in CVI have defects in response to RIL2, and at least in terms of defect of B cells, CVI is heterogeneous.

Polyclonal immunoglobulin secretion in patients with common variable immunodeficiency using monoclonal B cell differentiation factors.

B cells from 25 patients with common variable immunodeficiency (CVI) were tested for their ability to differentiate under the influence of B cell differentiation factors (BCDF), derived from T cell hybridomas or T cell clones. 11 patients generated Ig plaque-forming cells in the range comparable to that of normal controls with supernatant from the T cell hybrid MOP 1L. With various hybrid or clone supernatants, differing response patterns emerged. Four patients who failed to respond to MOP 1L responded to T cell clone supernatant RAC. Another who failed to respond to both MOP 1L and RAC responded to T cell hybrid supernatant MTP 7. These results indicate that these supernatants contain different BCDFs and suggest heterogeneity in the differentiation states of B cells in CVI. In addition, three patients demonstrated exaggerated responses to BCDF, and evidence was obtained from B cells of these patients for increased BCDF receptor density. Thus, the accumulated evidence indicates that T cell defects may be a primary pathogenetic mechanism in common variable immunodeficiency, and purified BCDF may be of therapeutic value.

Natural killer cells in common variable immunodeficiency and selective IgA deficiency

Natural killer (NK) cell activity was found to be above normal levels in patients with common variable immunodeficiency (CVID), whereas no NK cell abnormality was found in patients with selective IgA deficiency. The lytic activity of a given amount of peripheral blood lymphocytes was about five times higher in CVID patients than in controls when either K562, Molt 4, or Chang cells were used as targets. Interferon boosted the activity in patients and controls to about the same degree. NK activity was positively correlated to the number of circulating T8 + cells. Dysfunction of T cells, increase in suppressor cell function, and hyperactivity of NK cells in CVID may have a common background, possibly an abnormality related to interferon production.