IgG anti-IgA1 and anti-IgA2 antibodies: their measurement by an enzyme-linked immunosorbent assay and their relationship to disease

IgG anti-IgA antibodies were measured by an enzyme-linked immunosorbent assay using one IgA1 and one IgA2 (m1) myeloma and a pooled IgA protein preparation as antigens. Class-specific anti-IgA antibodies occurred in 0.8% of non-IgA-deficient sera and 24.3% of IgA-deficient sera. Antibodies reacting with IgA1 only occurred in 2.6% of non-IgA-deficient sera and 6.7% of IgA-deficient sera. Antibodies reacting with IgA2 only occurred in 0.6% of non-IgA-deficient sera and 2.7% of IgA-deficient sera. The prevalence of anti-IgA in IgA deficients with inflammatory disease was higher (81.8%) than in IgA deficients without disease (24.1%) and was accounted for by class-specific antibodies.     

Gm allotypes in IgA deficiency

Gm phenotypes were examined in 90 Swedish IgA-deficient (less than 0.05 g/litre of serum IgA) donors and 40 normal first and second degree relatives of six of these donors. The G1m1,2, G3m5 and Km1 frequency in the group of IgA-deficient donors did not differ from that found in the normal population. Among the relatives, HLA and/or Gm identical normal sibs were observed. Anti-IgA antibodies were present in 29 of the IgA-deficient donors and anti-IgG in seven. No association between the two was found. A statistically significant association between the G1m-2 phenotype and the presence of anti-IgA antibodies was observed. When subdivided according to HLA type, a non-random distribution of Gm phenotypes was seen in HLA-B8/DR3 positive individuals with anti-IgA antibodies (HLA-B8/DR3 being the haplotype associated with IgA deficiency). These data suggest an association between IgA deficiency, anti-IgA and the studied Gm allotypes.     

Anti-IgA antibodies in IgA-deficient children

IgG and IgM isotype antibodies to polyclonal human IgA, myeloma IgA₁, and myeloma IgA₂ were estimated in 38 IgA-deficient children aged between 0.9 and 15 years. All children had IgM anti-IgA antibodies. IgG antibodies against either polyclonal IgA, IgA₁, or IgA₂ were present in 63% of the IgA-deficient children. IgG anti-IgA antibodies were detected against all three antigens in 8 of 11 severely IgA-deficient children and in 7 of 27 partially IgA-deficient children, but in only 1 of 23 healthy adult controls. The proportion of children with IgG anti-IgA antibodies was significantly greater in the severely IgA-deficient group in comparison with the partially IgA-deficient group and the adult controls (chi-square test,P<0.01 andP<0.005, respectively). There was a strong correlation within each IgG subclass between antibody responses toward each of the three IgA antigens. Twenty-four children were followed over a period ranging from 0.9 to 11 years (mean, 2.3 years). Three children who were initially IgG anti-IgA antibody negative became antibody positive and three who were antibody positive became antibody negative. Five children with severe IgA deficiency remained severely IgA deficient and IgG antibodies to IgA persisted in all five at follow-up. The presence of IgG anti-IgA antibodies did not influence the normalization of serum IgA at follow-up in 14 of 19 children who were initially partially IgA deficient.     

Cross-reactive antibodies induced by xenogeneic IgA can cause selective IgA deficiency

Selective immunoglobulin A deficiency (sIgAD) is the most common immunodeficiency in humans. Auto-reactive antibodies to human immunoglobulin A (IgA) are found in the serum of 20–40% of individuals with sIgAD. It is unknown whether these antibodies play a role in the pathogenesis of this immunodeficiency and although the prevailing thought is that they are secondary to the onset of sIgAD, there is very little, if any, support for this notion. Here, we propose that anti-IgA antibodies are in fact responsible for the removal of IgA from serum, and that the inducing antigen is most probably a xenogeneic IgA. This hypothesis is based on data obtained from an sIgAD patient in whom changes in dietary consumption of beef and/or bovine dairy products resulted in changes in anti-IgA levels in the serum. To test the hypothesis, the presence of anti-bovine IgA antibodies was tested by a highly specific enzyme-linked immunosorbent assay in serum samples from IgA-deficient and control individuals. All 13 sIgAD individuals with anti-IgA antibodies had a higher titer against bovine IgA than against human IgA. Of 23 control individuals, a surprisingly high proportion (65%) was also found to have IgG anti-bovine IgA antibodies. These results support the hypothesis that the anti-human IgA antibodies found in IgA-deficient individuals are originally produced against bovine IgA. These antibodies are found in many normal individuals, but only in cases where they cross react with endogenous human IgA, sIgAD may develop.     

Lmmunobiology of human anti-lgA: a serologic and immunogenetic study of immunization to IgA in transfusion and pregnancy*

Human antibodies to human IgA are detected by a sensitive passive hemagglutination assay using IgA paraproteins. The antibodies have a dichotomy of specificities: (1) class-specific with titers frequently higher than 1:1000 produced by persons lacking IgA, and (2) antibodies with limited specificity (titers less than 1:256) produced by persons with normal IgA when repeatedly transfused. Either type of anti-IgA belonging to the IgG class was present in 86 per cent of the patients with anaphylactoid and urticarial transfusion reactions, which was consistent with binding of the complement by such antibodies. Anti-IgA antibodies were detected in 16 per cent of the cases with multiple transfusions received during openheart surgery procedure; they also have a significantly high incidence in the sera of recently delivered women. One fetus had IgM anti-IgA, probably as a result of immunization to maternal IgA. Serum obtained from a Caucasian woman before and after an anaphylactoid reaction to a blood transfusion contained anti-IgA antibodies of limited specificity of the IgG class, possibly as a result of isoimmunization in pregnancy. The patient's serum was used as an agglutinator in passive hemagglultination assays on normal serum, which resulted in the definition of Am(l), the first genetically determined allotype of human IgA. On the basis of serologic and immunochemical evidence, Am(1) was localized in the a chains. Based on its gene frequencies and on family studies, Am(l) was established as a mendelian dominant trait. The isoantigen is associated with γA₂ subclass but not with the serum γA₂ levels. Am(1) is different from the other allotypes of human immunoglobulins, the Gm and Inv types. Am(1) is detectable in salivary IgA; it was not detectable in cord sera. Its polymorphism makes it suitable for studies of population genetics and the molecular biology of IgA.     

An enzyme immunoassay for the determination of low levels of IgA in human serum

An enzyme immunoassay (EIA) has been developed which facilitates the detection of low levels of immunoglobulin A in human serum. IgA is captured by an anti-IgA antibody linked to micron-sized polyacrylamide beads and subsequently detected by an anti-IgA horseradish peroxidase conjugate. The standard curve is linear in the region between 25-1000 ng/ml IgA. The assay is particularly suited to measure IgA antibodies in sera from IgA-deficient individuals and IgA contaminants in blood products.     

Anti-IgA in Selective IgA Deficiency

Anti-IgA antibodies were found in 14 of 33 (42%) IgA-deficient donors. In healthy IgA-deficient blood donors anti-IgA appeared associated with the presence of HLA DR3. The antibodies were mainly of the IgG1 and, in high-titred sera, IgG4 subclasses. Sera containing high-titred anti-IgA selectively impaired IgA synthesis in vitro as induced by direct and indirect polyclonal B-cell activators. These antibodies may play a role in the pathogenesis and/or the maintenance of IgA deficiency.     

Inadequacy of musocal IgM antibodies in selective IgA deficiency: Excretion of attenuated polio viruses is prolonged

A nationwide vaccination campaign with oral poliovirus vaccine was organized in Finland in 1985 in order to cease an outbreak of poliomyelitis. We followed eight IgA-deficient individuals and nine controls for poliovirus excretion in feces and for antibody responses in serum and saliva. Five weeks after oral poliovirus vaccination all eight IgA-deficient individuals were still excreting polioviruses, in contrast to one of nine controls. The concentration of polioviruses, as estimated by a semiquantitative immunofluorescent assay, was generally higher and the test was significantly more often positive in the samples from the IgA-deficient individuals. Although serum levels of antibodies to poliovirus type 3 were lower in IgA-deficient individuals before vaccination, both measurements showed that the two groups had similar antibody levels 4 weeks after vaccination. IgA-deficient individuals lacked salivary IgA antibodies to poliovirus types 1 and 3 but had increased levels of IgM antipolio antibodies, which were shown to carry secretory component. We conclude that the mucosal IgM antibodies of IgA-deficient individuals eliminate polioviruses less efficiently than do the IgA antibodies of normal individuals.     

Anti-IgA antibodies in selective IgA deficiency and in primary immunodeficient patients treated with gamma-globulin

Sera from 106 blood donors, 40 patients with primary immunodeficiencies (ID) treated with gamma-globulin, and 46 patients with selective IgA deficiency were analyzed by an enzyme-linked immunosorbent assay for anti-IgA antibodies. Increased levels of antibodies to IgA were found in 5.6% of the blood donors, 17.5% of the ID patients, and 36.8% of the isolated IgA deficiencies. The percentage was higher in patients with IgA and IgG2 deficiencies (50%). The percentage of patients having increased levels of anti-IgA antibodies was similar to the total prevalence of the 10 other autoantibodies studied. These anti-IgA antibodies were mainly of the IgG class, except from one blood donor with IgM antibodies, and two patients, one with isolated IgA deficiency and the other with common variable immunodeficiency who had anti-IgA antibodies of the IgE class. The latter patient developed a near fatal anaphylactic reaction when intravenous gamma-globulin was administered. Most of the patients with severe adverse reactions to gamma-globulin did not present anti-IgA antibodies. Our data suggest that at least in some immunodeficient patients the elevated amounts of anti-IgA antibodies are not related to the administration of exogenous IgA. The importance of measuring anti-IgA antibodies of the IgG and IgE isotypes in IgA-deficient patients as well as in patients in treatment with gamma-globulin is emphasized.     

The role of anti-IgA antibodies in causing adverse reactions to gamma globulin infusion in immunodeficient patients: a comprehensive review of the literature

Anaphylactic reactions to immunoglobulin infusions in immunodeficient patients with undetectable IgA have been attributed in several reports to IgG or IgE anti-IgA antibodies. However, other reports have not supported an association between such antibodies and the development of severe reactions. We have reviewed the articles reporting reactions to immunoglobulin products in IgA-deficient patients, as well as those describing the presence of such antibodies in the absence of reactions to infusions. A?variety of factors might influence the association of adverse reactions with anti-IgA antibodies, including the serum concentration and isotype (IgG or IgE) of the anti-IgA antibody, its specificity (class or subclass specific), the method of measurement, and the IgA content of the gamma globulin infusion and its route of administration. The role of anti-IgA antibodies in causing anaphylaxis in IgA-deficient patients receiving gamma globulin therapy is still controversial. Larger (multicenter) studies are needed to further evaluate this association.     

Immunoglobulin prophylaxis in patients with antibody deficiency syndromes and anti-IgA antibodies

Sera from three hundred five patients with immunoglobulin deficiencies were analyzed for the presence of anti-IgA antibodies by using indirect agglutination and enzyme-linked immunosorbent assay (ELISA). Anti-IgA antibodies were observed in 15 of 68 (22%) patients with hypogammaglobulinemia and 53 of 185 (29%) patients with selective IgA deficiency, both groups having serum IgA<0.05 g/liter. The highest frequency, 6 of 10 or 60%, was noted for patients with a combined IgA-IgG2 deficiency. No anti-IgA antibodies were detected in 25 patients with serum IgA between 0.05 and 0.27 g/liter and normal amounts of serum IgM and IgG or in 17 patients with hypogammaglobulinemia who had serum IgA of 0.05–0.7 g/liter. The anti-IgA antibodies were primarily of the IgG class, but IgD and IgM anti-IgA were occasionally found. IgE anti-IgA antibodies could not be detected with the presently used technique. The IgG anti-IgA antibodies were mainly of the IgG1 subclass but occasionally also of the subclasses IgG2, IgG3, and IgG4. Of eight patients with anti-IgA antibodies, seven tolerated Ig prophylaxis with a commercial immunoglobulin preparation low in IgA when given either intramuscularly or intravenously. The titers of anti-IgA in the sera of these patients did not rise in relation to the prophylaxis. Only one of the eight patients had a history of previous anaphylactic reactions to IgA-containing blood products. He tolerated six Ig infusions during 5 months with the IgA-depleted preparation without any adverse effects but showed increasing levels of anti-IgA antibodies and ultimately experienced a near-fatal reaction at the seventh infusion.     

IgA and IgG Subclass Deficiency in a Poor Population in a Developing Country

The levels of IgG, IgG subclasses, IgM and IgA were determined in serum from 17 patients with IgA deficiency and severe or frequent infections, allergy and/or autoimmunity (median age 7 years, range 2–19), 11 healthy IgA-deficient adults and 35 controls (median age 7 years, range 2–19). In serum from all groups IgG, IgM and IgA antibodies were determined against β-lactoglobulin, E. coli O antigens and poliovirus type 1 antigen. In saliva of 15 IgA-deficient patients and 12 of the controls IgG, IgM and secretory component-carrying antibodies against E. coli O antigens and poliovirus type I were determined. The majority of the studied individuals lived under poor socio-economic conditions in Brazil, with consequent heavy microbial exposure. One IgA-deficient patient with rheumatoid arthritis also had IgG2 deficiency but no infectious problems. Four out of the 35 controls without any obvious infectious problems were found with IgA or IgG subclass deficiency. One of the 11 healthy IgA-deficient adults was low in the IgG2 subclass, one in IgGl and one in IgG3. Those with symptomatic IgA deficiency had significantly higher serum IgG than the controls, especially in the age group 6–11 years. This latter group also had significantly increased serum IgG 1 and IgG2 levels when compared with the age-matched controls. Salivary IgM antibodies to E. coli and poliovirus antigens were significantly higher among the symptomatic IgA-deficient individuals than among the controls. It is not clear at present whether these increased Ig levels are secondary to frequent infections and/or part of mechanisms that may compensate for the IgA deficiency.     

Long-term follow-up of anti-IgA antibodies in healthy iga-deficient adults

A follow-up study of anti-IgA antibodies in 159 healthy blood donors with severe deficiency of serum IgA (<0.05 mg/L) and in 45 donors with decreased serum IgA levels (0.05–799 mg/L), identified in 1971–1980, was carried out. Initially anti-IgA antibodies were determined by a hemagglutination (HA) method and two reexaminations were done in 1990–1992 by an enzyme immunoassay. The median follow-up period was 19 years, during which anti-IgA level was changed considerably in only four persons, increased in two, and high level antibodies (>1/1000 by HA) appeared in two. In reexaminations anti-IgA antibodies were found in 30 (19%) subjects with severe IgA deficiency and the antibody levels remained relatively constant in those who had high and medium antibody levels. Anti-IgA antibodies were not found in subjects with decreased, but detectable serum IgA. Thus it seems that only those healthy adults who have severe IgA deficiency develop anti-IgA antibodies and their anti-IgA levels remain fairly constant Of the 159 subjects with severe IgA deficiency, 66 had a history of IgA exposure, but no correlation to anti-IgA development was noted.Portions of the work have been presented in a poster form at the XXIIIrd Congress of the International Society of Blood Transfusion in Amsterdam, the Netherlands, July 2–9, 1994.     

Anti-IgA antibodies in epileptic patients with a low serum IgA concentration

Sera from 22 phenytoin-treated epileptic patients with a serum IgA less than 0.30 g/l were examined for anti-IgA antibodies using an ELISA. Only one patient had a complete IgA deficiency. Anti-IgA antibodies of restricted specificity were detected in serum from two of the patients. Their serum IgA concentrations were 0.03 and 0.27 g/l. The serum concentrations of IgM, IgG and the IgG subclasses were normal in both these patients. The frequency of this type of anti-IgA antibody is not higher in epileptic patients with a low serum IgA than in healthy controls, and class-specific anti-IgA antibodies are not a pathogenetic factor in the IgA deficiency occurring in epilepsy.     

Serum IgA deficiency and anti-IgA antibodies in pernicious anemia

Three pernicious anemia (PA) patients with selective IgA deficiency and anti-IgA antibodies in their sera were followed for over 3 years. After instituting therapy with cyanocobalamin there was a slight increase in the anti-IgA antibodies. After 1 year the titers of anti-IgA antibodies in the sera of these patients declined significantly as compared to the values before treatment (P less than 0.02), and after 2 years one patient had no measurable anti-IgA antibodies, yet no IgA appeared in the serum of any of the three. Further, in a medium with no anti-IgA the lymphocytes of these patients were not capable of producing IgA in vitro. Thus, the reason for the IgA deficiency in PA appears to be linked to the function of B cells rather than to anti-IgA antibodies.     

Recurrent extended HLA haplotypes in children with selective IgA deficiency

HLA supratypes as well as serum IgG, IgA and IgM levels were determined in 44 children and adolescents with severe IgA deficiency (serum IgA less than 5 mg/dl) and in first degree relatives. Frequencies of the HLA alleles B14, DR1, DQW1, C4A2 and C4B2 were significantly higher in the IgA-deficient patients than in the controls. The most recurrent haplotype among patients was B14, DR1 (p less than 10(-4) preferentially associated with A33, A28 or A blank. The supratype B14, Bfs, C4A2, C4B2, DR1, DQW1 was present in a 14-fold higher frequency than in the controls, and strongly suggests the presence of a gene in the HLA region involved in the deficiency of IgA. The fact that this supratype was not always associated with IgA deficiency in the parents and that not all IgA-deficient subjects had this supratype is discussed. Severe IgA deficiency was found in four mothers (two of the four mother-child pairs shared the B14, DR1 haplotype); three other relatives (one father and two brothers) had partial IgA deficiency and did not have the B14, DR1, DQW1 haplotype.     

Serum IgE levels in patients with selective IgA deficiency.

In this study serum IgE levels were measured by a double-antibody radioimmunoassay in 31 patients with serum IgA concentration less than 0.01 mg/ml who were followed in the arthritis and allergy clinics. On a group basis there was no significant difference in mean serum IgE levels between the IgA deficient patients and normal subjects of the same age. However, in the absence of atopic disease, IgA deficient patients had significantly lower serum IgE levels. When atopy was associated with IgA deficiency IgE levels were the same as in the normal subjects but significantly lower than those of atopic non-IgA deficient patients. IgE levels in those with recurrent respiratory tract infection were not different. Adults with anti-IgA antibodies had significantly lower IgE values. IgE levels in patients with RA, JRA or SLE were not significantly different. Selective IgA deficient patients may have a relative deficiency of serum IgE depending on the comparison group.     

The transformation of human lymphocytes by monkey antisera to human immunoglobulins

Cultures of human peripheral leucocytes were stimulated to incorporate tritiated thymidine when incubated with monkey antisera to human immunoglobulins. Twenty-five of forty-four monkey antisera were active and stimulated 90 per cent of leucocyte (WBC) cultures to incorporate a small but significantly greater amount of tritiated thymidine (TdR³H) than that incorporated by controls. This stimulation of TdR³H uptake correlated with an increase from 2 to 8 per cent lymphoblasts in the cultures. Leucocytes washed free of serum immunoglobulins responded to a greater degree to the anti-immunoglobulin sera than when they were cultured in the presence of human serum. Prior absorption of antisera with either whole serum or homologous immunoglobulin blocked antiserum stimulation completely. The anti-IgG and anti-IgM antisera were consistently more effective than anti-IgA, anti-κ and anti-λ chain antisera. Sequential stimulation by antisera against two different immunoglobulins was not significantly different from those stimulated by only one of the two. Lymphocytes from three asymptomatic subjects with low or absent serum IgA levels transformed as well with anti-IgA as did lymphocytes from subjects with normal serum IgA levels. Antisera were cytotoxic to the lymphocytes only in the presence of complement. Presumably the transformation of human lymphocytes was due to a reaction of anti-immunoglobulin antisera with specific immunoglobulin antigenic determinants present on or in the circulating lymphocytes.     

Review: IgA anaphylactic transfusion reactions. Part I. Laboratory diagnosis, incidence, and supply of IgA-deficient products

Despite yielding a definitive diagnosis in fewer than 20 percent of anaphylactic transfusion reactions, investigation for IgA deficiency and the presence of presumably pathogenic IgG anti-IgA is useful in patient management. Individuals with demonstrated anti-IgA are thereafter committed to receiving IgA-depleted cellular products or IgA-deficient plasma and derivatives to prevent recurrent severe reactions. Unfortunately, in populations of IgA-deficient individuals screened for anti-IgA, the predictive value of the test in the absence of a prior reaction is quite low. Anti-IgA testing is complex and limited to a few reference laboratories, many of which still employ a labor-intensive hemagglutination assay developed in the late 1960s. Timely decisions regarding further transfusion management of patients experiencing anaphylaxis often rely upon more rapidly obtained assays of the IgA concentration as an indicator of the likelihood of subsequent demonstration of anti-IgA. The scarcity of IgA-deficient banked plasma products and dedicated plateletpheresis donors has led to the development of American Rare Donor Program policies designed to appropriately allocate these precious resources. The test methods used to establish the diagnosis of IgA deficiency and identify the approximately one third of these individuals with anti-IgA are discussed, along with the incidence of abnormal tests in various populations. Also presented are testing recommendations for the identification of an IgA-mediated mechanism for transfusion-associated anaphylaxis and qualification of patients to receive rare IgA-deficient plasma-containing products.     

Familial selective IgA deficiency with circulating anti-IgA antibodies: a distinct group of patients?

Two families were investigated in which the mothers had selective IgA deficiency and circulating class-specific anti-IgA antibodies. Both gave birth to two children who were found to be IgA deficient. Three of these children developed anti-IgA antibodies before puberty. In vitro immunoglobulin production studies performed in the children of both families revealed an IgA B cell defect combined with IgA-specific excessive T suppressor function in all four. The mechanisms by which transplacental passage of maternal anti-IgA antibodies could have interfered with the developing IgA system in the offspring are discussed.