Common variable immunodeficiency and Evans syndrome complicated by autoimmune hemolysis due to anti-Jka auto-antibodies

Common variable immunodeficiency (CVID) is a syndrome characterised by generalised defective antibody production and recurrent infections. A marked decrease in serum IgG associated with significant reduction of IgM and/or IgA levels is the hallmark of the disease [1]. Patients with CVID are at increased risk of developing autoimmune disorders and malignancy, as a consequence of abnormal immune regulation as well as immunodeficiency [2]. Treatment options include corticosteroids and intravenous immunoglobulin [3]. Twenty percent of patients with CVID develop clinical features suggestive of autoimmune disease. Our report is the first case of CVID and Evans syndrome, complicated with autoimmune hemolysis due to anti-JKa auto-antibodies.

A 54-year-old man with a diagnosis of CVID was admitted to our hospital in August 2007 with a severe Coombs-positive autoimmune hemolytic anemia (AIHA). He reported jaundice, fatigue and symptoms and signs of anemia in the days preceding admission. Laboratory studies showed normal platelet and white blood cell counts with a normal differentiation, but severe anemia (Hb of 6.5 g/dL) with reticulocytosis was found. As bilirubin (5.32 mg/dL) and LDH (480 UI/L) were all elevated, hemolysis was suspected. The patient had a positive direct anti-globulin test (DAT) with IgG (−), IgA (−), IgM (−) C3d(+) and a serum auto-antibody with anti-JKa specificity in the eluate prepared from his red blood cells. Indirect anti-globulin test (IAT) also was positive.

Serum immunoglobulin levels were IgG 441 mg/dL, IgA 22 mg/dL, IgM 22 mg/dL and IgD 4 UI/L. Low serum levels of IgG1 262 mg/dL, IgG2 93 mg/dL and IgG4 0.36 mg/dL were also found. Serum protein electrophoresis showed hypogammaglobulinemia with no evidence of monoclonal gammopathy. C4 10 mg/dL and C3 74 mg/dL fractions of complement were low. Anti-nuclear antibodies, Mycoplasma and viral serologies were negative but anti-platelet antibodies against GP IIb/IIIa, Ib/IX and Ia/IIa were found. Normal levels of CD4, CD8 T cells and B cells were detected; however significant low levels of NK cells were observed (Table I). When dissecting the B cell compartment that comprises 3.2% (195 cells/µL) of peripheral blood cells (PBLs) according to surface Ig and CD27 expression, we detected a significant decrease in the class switched IgD-CD27+ memory B cells containing only 0.18% (3 cells/µL). The remaining memory B cells 1.62% (99 cells/µL) of PBLs corresponded to non class switched CD27+IgD+ B cells. Within this last memory subpopulation the majority of cells expressed CD27+IgM+IgD+ phenotype (48.81%), suggesting an expansion of splenic marginal zone memory cells B (Table II).

Table I.  T cells, B cells and NK cells counts by flow cytometry in whole peripheral blood.

	% Whole blood cells	Cells (mL)	Normal range cells (mL)
T cells	10.7	653	933 – 2491
CD4+ T cells	7.4	451	370 – 1468
CD8+ T cells	3.0	283	183 – 799
NK cells	0.3	18	60 – 495
B cells	3.2	195	65 – 595

Table II.  Analysis made in CD19+ B cells from peripheral blood.

Subpopulations in Memory B cell compartment	Percentage
Memory B cells (CD27+)	56%
Non-Switched Memory B cells (CD27+IgM+)	50.93%
Switched Memory B cells (CD27+IgD−)	5.93%
SMZ B cells (CD19+IgM+IgD+CD27+)	48.81%

The patient had a history of CVID diagnosed 18 years prior to admission and complicated by splenomegaly, pyogenic skin infections, respiratory infections, neutropenia, immune thrombocytopenic purpura (ITP) and autoimmune hemolytic anemia (Evans syndrome), that had been treated with IVIG and steroids with good response. At the time of admission he was only receiving 15 mg/day of prednisone. The patient received the last dose of IVIG in April of 1997 in order to treat hematological complications.

He had a positive transfusion history for platelets and fresh frozen plasma; however, he had never been transfused with red blood cells. The phenotype of red cells of the patient showed a JKa positive antigen in self-erythrocytes. He responded to treatment with prednisone 1.5 mg/kg and IVIG (400 mg/kg/d). After 4 days of treatment his Hb concentration increased to 11 g/dL.

The Kidd (Jk) blood group system is composed of the Jka and Jkb antigens that differ by a single amino acid (Asp280Asn) and are responsible for the common Jk (a+b−), Jk (a−b+) and Jk (a+b+) phenotypes. Anti-Jk antibodies are uncommon, but they are responsible for at least one third of the cases of delayed hemolytic transfusion reaction. Interestingly, only a few cases of autoimmune hemolysis due to anti-Jka antibodies have been described and neither was associated with immune deficiency states like CVID [4],[5]. We suggest that an overall reduction in antibody production could contribute to generate pathogenic auto-antibodies and autoimmune manifestations in CVID. While most patients with CVID have normal numbers of B cells, these fail to differentiate into productive immunoglobulin secreting cells [6], which can induce a profound alteration in the idiotypic networks, B cell populations and immunoglobulin repertoire. According to Jerne's theory of idiotypic network, the antigen binding site of antigen specific antibodies stimulates the immune system to generate anti-idiotypic antibodies [7]. Adult serum, contains antibodies capable of interacting through V regions of antibodies within the same individual's IgG fraction of serum, and some of them can bound auto-antibodies directed against self-antigens. In patients with CVID, the limited production of IgG, and occasionally IgM, might lead to insufficient production of anti-idiotypic antibodies capable of blocking the generation of a pathogenic auto-antibody. We believe this was the case in our patient with anti-JKa auto-antibodies. Anti-idiotypes against auto-antibodies have been detected in normal immunoglobulins, a finding which provides a plausible mechanism of action justifying the use of IVIG in autoimmune diseases [8], including those associated with CVID.

Interaction of anti-idiotype antibody with surface immunoglobulins may activate or induce anergy in B-lymphocytes and participate in shaping the repertoire of B cells [9]. In patients with CVID this network is likely to be impaired by the inability to produce enough immunoglobulins. Another important mechanism capable of eliminating autoreactive clones is the negative selection of self-reactive B cells in bone marrow (BM). In this process complement contributes to the retention of highly conserved self-antigens in immune complexes which leads to enhanced recognition by immature self-reactive B cells resulting in anergy or apoptosis [10]. This hypothesis explains that self-antigen retention could be mediated by complement receptors CD21/CD35 expressed on BM stroma [10] and other antigen presenting cells [11]. This model is now supported by the fact that human BM dendritic cells and macrophages produce the first component of the classical pathway of complement activation C1q [12]. Interestingly, CD21 are expressed during human B cell differentiation [13] and in circulating splenic marginal zone B cells [14]; however, in a subset of CVID patients an abnormally increased percentage of CD21 (−) B cells is associated with higher rate of splenomegaly and autoimmune cytopenias [15]. Defective interaction of CD21 (−) B cells with complement-bound immunecomplexes might interfere with central tolerance mechanisms and thereby contribute to the selection of auto reactive clones.

This inability to form immune complexes might also predispose to autoimmunity in CVID. Moreover, IgM⁺IgD⁺CD27⁺ B cells could correspond to circulating splenic marginal zone B cells exhibiting a rapid activation and immunoglobulin secretion in response to blood-borne T independent antigens [16] and could participate in autoimmune responses. We speculate that the lack of immune complexes that exert immunoregulatory functions by binding to receptor structures such as Fc receptors, the B-cell receptor (BCR), or complement receptors in marginal zone B cells might produce auto-antibodies to blood borne antigens.

IVIG might provide a protective effect through an idiotype – anti-idiotype mechanism, downregulating the autoreactive-anti-Jka B cell clone while stimulating the production of immune complexes that enhance negative selection of autoreactive B cell clones in BM and spleen.