Selective IgG subclass deficiency: quantification and clinical relevance

Each of the four human IgG subclasses exhibits a unique profile of effector functions relevant to the clearance and elimination of infecting microorganisms. The quantitative response within each IgG subclass varies with the nature of the antigen, its route of entry and, presumably, the form in which it is presented to the immune system. This results in antibody responses to certain antigens being predominantly or exclusively of a single IgG subclass. An inability to produce antibody of the optimally protective isotype can result in a selective immunodeficiency state. This is particularly apparent for responses to certain bacterial carbohydrate antigens that are normally of IgG2 isotype. A failure to produce the appropriate specific antibody response may result in recurrent upper and/or lower respiratory tract infection. Careful patient investigation can identify such deficiencies and suggest appropriate clinical management. In this review we outline the biology and clinical relevance of the IgG subclasses and summarize current rational treatment approaches.

Variable expression of IgG2 deficiency

Sustained and significant reversal of antibody deficiencies is uncommon, although it has been noted in some cases during childhood and after viral infections. We report a case of reversal of IgG2 deficiency after splenectomy. A 46-year-old man who suffered recurrent sinusitis despite antibiotic therapy was noted to have IgG2 deficiency and cutaneous anergy. Replacement therapy with intravenous immunoglobulin ameliorated his symptoms. After 13 months of therapy, the patient had a diagnostic laparotomy and splenectomy because of portal hypertension, hypersplenism, and consideration of underlying malignancy. No evidence of malignancy or infection, including human immunodeficiency virus, active cytomegalovirus, or Epstein-Barr virus infection, was found. After splenectomy, the patient's serum IgG2 level normalized without replacement therapy. Subsequently, it fell, then normalized once more, and remains normal. The patient also demonstrated positive reactions to delayed hypersensitivity testing after splenectomy, but, subsequently, became anergic and remains anergic at the present time. Since the splenectomy he has remained clinically well without antibiotics or immunoglobulin replacement. In vitro analysis of his lymphocyte function demonstrated impaired T cell proliferation as well as an intrinsic B cell differentiation defect. This case demonstrates the potentially dynamic nature of IgG subclass deficiencies.

[Hypogammaglobulinemia G and A with hypergammaglobulinemia M. Apropos of 12 cases]

Hyper IgM with low IgG and IgA is a rare humoral immunodeficiency. We presently report 12 new observations which have been clinically and immunologically studied. On one occasion the syndrome was found to be associated with congenital rubella. Since 10/12 children were male, X-linked inheritance is suggested which has been confirmed in 2 cases. In most cases (9/12), the first infections occurred within the first year of life. The syndrome is causing upper and lower respiratory tract infections due to bacteria, as well as gut infections. Lymphoid organ hyperplasia has been noted in 11/12 patients. Polyclonal hyper IgM serum contrasts with low or absent IgG, IgA and IgE. In some instances, some IgM antibody response was detected. A dysfunction of cellular immunity was not detected. Autoimmunity was detected in 3 patients. Finally, transient neutropenia occurred in 50% of the patients. Intravenous immunoglobulin G substitution treatment resulted in a significant reduction in the occurrence of infections as well as in normalization of growth rate. Immunoglobulin infusion also frequently induced correction of hyper IgM and neutropenia.

[Intravenous immunoglobulin in the treatment of malignant epilepsy in children]

15 children with malignant epilepsy showing no response to conventional antiepileptic drugs or hormone therapy were administered intravenous immunoglobulin (Endobulin, Immuno) at a dosage of 400 mg/kg per day on the 1st and 15th day and subsequently every three weeks for 6 months. 7 of these 15 patients showed IgG2 subclass deficiency. A significant reduction in attacks, or even absence of attacks was observed in 10 out of 15 children after six months of intravenous immunoglobulin therapy. Apart from one patient with ringchromosomopathy, all the children with IgG2 subclass deficiency responded to this therapy. The reduction of attacks after i.v. immunoglobulin therapy correlates with the improvement or normalization of the EEG findings. At present, the authors consider the number of patients still too small to make a final assessment, but they believe that intravenous immunoglobulin holds an important position in the treatment of malignant epilepsy in childhood.

[Selective deficiency of IgA]

The selective deficit of IgA is the most frequently acquired immunodeficiency. It is important because of this and the variability of the clinical presentation, which might be non-symptomatic or simply show several clinical features. The prognosis depends on the associated clinical affliction. There is no substitute treatment for this immunodeficiency, in which the immunoglobulins administration produces a paradoxical antibody formation against this, and adverse immunological reactions. We reviewed the immunodeficiency in this paper, highlighting the frequency, pathogenia, clinical diversity and therapy.

Patients with Igg subclass and/or selective antibody deficiency to polysaccharide antigens: initiation of a controlled clinical trial of intravenous immune globulin

Selective IgG subclass deficiencies and/or selectively impaired antibody responses to bacterial capsular polysaccharide antigens have been increasingly reported. In this report, 13 children with recurrent infections and deficient antibody responses to polysaccharide antigens are described. Serum IgG2 subclass concentrations were normal in all the patients, and two children had low IgG3 levels. Mean serum antibody concentrations to the capsular polysaccharide antigens of Streptococcus pneumoniae and Haemophilus influenzae were significantly decreased after immunizations, but antibody responses to diphtheria and tetanus toxoids were normal. The identification of children with selective antibody deficiencies and recurrent infections has prompted a multicenter, double-blind, placebo-controlled study to evaluate the efficacy and safety of intravenous immune globulin therapy in these patients.

Selective IgG subclass deficiencies in patients with recurrent sinopulmonary infections: report of two cases

Two patients with recurrent sinopulmonary infections and normal total serum immunoglobulin levels were found to have selective deficiencies in IgG subclasses. The serum of one patient contained abnormally low IgG2 and IgG4; and the other was deficient in IgG4. Both patients responded to the treatment with high dose intravenous immunoglobulin. The experiences on these two cases strongly suggest that IgG subclasses should be checked in patients with recurrent sinopulmonary infections in face of normal total immunoglobulins.

New and controversial uses of intravenous gamma-globulin

During the last few years the use of intravenous immunoglobulin (IVIG) has attracted increasing interest for the treatment of patients who do not have a classical humoral antibody deficiency syndrome. In certain situations this approach has revolutionized medical management, e.g. in immune thrombocytopenia. In other areas, such as in Kawasaki's syndrome, IVIG therapy have been shown to be highly beneficial in preventing long term disease sequelae by some investigators, but the field remains controversial. Conditions under which IVIG therapy has been shown to be of potential benefit are: (1) intractable childhood epilepsy; (2) autoimmune diseases, e.g. myasthenia gravis, systemic lupus erythematosus, idiopathic thrombocytopenic purpura, idiopathic neutropenia and aplastic anemia; (3) atopic allergy with IgG subclass deficiency including bronchial asthma; (4) in severe infections in combination therapy with antibiotics and as an antipyretic; (5) in Kawasaki's disease; (6) in multiple myeloma and chronic lymphocytic leukemia. Oral and intraventricular administration of IVIG have also been tried, the former for severe diarrhea and the latter to try to rescue the central nervous system from damage by a pathogen. Carefully controlled clinical trials are needed to establish the efficacy of gamma-globulin therapy in these and other conditions.

Intravenous immunoglobulin prophylaxis causing liver damage in 16 of 77 patients with hypogammaglobulinemia or IgG subclass deficiency

Sixteen of 77 patients (21 percent) with common variable immunodeficiency or IgG subclass deficiency contracted non-A, non-B hepatitis in association with intravenous infusions of immunoglobulin. The hepatitis seemed to run a more severe course in these patients than in non-immunodeficient patients. Twelve patients had clinical symptoms, and five died with hepatitis being the cause of death in two and a contributing factor in three. Liver biopsy specimens showed early chronic active hepatitis and cirrhosis. In addition to increases in liver enzymes, 13 patients had increases in alkaline phosphatase levels. All but two patients who contracted hepatitis had been given 50 mg/kg per week or more of intravenous immunoglobulin. Lymphocyte counts, T/B cell ratios, and T-lymphocyte function did not differ between those in whom hepatitis developed and those in whom it did not develop. The hepatitis was associated with more than one batch of a Swedish intravenous immunoglobulin, the immunoglobulin being derived from United States sources as well as from European plasma. Three previous brief reports in the literature have also associated non-A, non-B hepatitis with the intravenous infusion of various immunoglobulins. Biologic materials given to patients, including immunoglobulin, should, whenever possible, be prepared so as to ensure absence of viruses.

[Clinical relevance of immunoglobulin subclasses in children with chronic pulmonary diseases]

In 52 children (age 4-19.5 years; 17 female, 35 male) with chronic chest symptoms IgG-Subclass levels were measured by radial immunodiffusion techniques. Thirteen children had proven bronchiectasis, 22 chronic bronchitis and 17 steroid dependent asthma bronchiale. Cystic fibrosis, alpha-1-antitrypsin deficiency, tuberculosis and chronic foreign bodies were excluded in each patient; all of them showed normal levels of total IgG. Four children (3 with bronchiectasis, one with steroid dependent asthma bronchiale) had a complete lack if IgG4. In two children with chronic bronchitis one showed fluctuating levels of IgG2 and IgG4 and another deficiency of IgG3. All patients with an isolated IgG4 deficiency were treated with immunoglobulins. Of 3 patients with bronchiectasis one improved, two remained unchanged as shown by positive sputum cultures and of chronic chest symptoms. One patient with steroid dependent asthma bronchiale markedly improved during immunoglobulin therapy. It is concluded, that early screening of IgG subclass deficiency is indicated in all children with chronic chest symptoms.

The use of intravenous immunoglobulin for the treatment of infection: an overview

Immunoglobulin replacement therapy in the form of intravenous immunoglobulin (IVIgG) is clearly of benefit in primary hypogammaglobulinaemia and related disorders involving antibody deficiency. However, its use in the prevention of infection in other conditions is controversial and needs to be clarified. IVIgG therapy may be of benefit in selected patients with IgG subclass deficiency, and with a proven history of recurrent upper respiratory tract infections. IVIgG therapy may also benefit infants with AIDS and recurrent bacterial infections, but is only rarely of value in cases of adult AIDS. The use of 'normal' IVIgG from unselected blood donors to treat viral infections, infections due to gram negative organisms, or to neutralise endotoxin, is probably not indicated on theoretical and practical grounds, and because of the high cost. IVIgG preparations derived from plasma donations selected for high specific antibody levels to the relevant microorganism will probably be of greater benefit than normal IVIgG in patients with specific infections.

An investigation into the effect of the IgG antibody system on the susceptibility of IgA-deficient patients to respiratory tract infections

Serum IgG subclass concentrations and IgG-tetanus toxoid antibody (IgG-TTab) responses were measured in IgA-deficient patients with severe respiratory tract infections (n = 11), mild respiratory tract infections (n = 5) or no increased susceptibility to respiratory tract infections (n = 15). The severe infection group had lower IgG2 concentrations than the patients without infections (P less than 0.02) and was the only group with IgG2-deficient patients (36%). The number of sera in which IgG4 was not detected was higher in patients with severe infections than in both normal controls (45% vs 10%, P less than 0.01) and the other IgA-deficient patients (45% vs 20%), in part explained by a strong association with IgG2 deficiency. Subnormal IgG-TTab responses were demonstrated in 45% of patients with severe infections but in only one patient from each of the other two groups. Five patients with IgG2 deficiency and/or subnormal IgG-TTab responses were treated with gammaglobulin and apparently improved. There was a high serum concentration of IgG1 in 35% and IgG3 in 19% of the 31 patients, predominantly in those without severe infections. Thus a proportion of IgA-deficient patients have additional defects of IgG; IgG1 and IgG3 antibody responses may compensate for the IgA deficiency in asymptomatic patients.