No abstract

Low levels of single or multiple serum immunoglobulin G (IgG) subclasses is a common finding among patients with increased susceptibility to infections. In this investigation we summarize data from studies of 503 subclass-deficient individuals. Low IgG2 levels was the most common deficiency among children, and boys were more often deficient than girls. From the age of 16, females dominated, and the most frequent finding was low IgG3 levels. In vitro T or B lymphocyte dysfunction was demonstrated in 75% of the individuals, suggesting that low subclass levels may be indicators of an underlying defect at the B cell or possibly T cell level. Vaccinations and mucosal biopsies were performed to evaluate which patients may be helped by immunoglobulin substitution therapy.

No abstract

Persistent low serum levels of one or several immunoglobulin G (IgG) subclasses can be found in a high proportion of adult patients with increased susceptibility to infections. It is hard to envision that the low subclass level in itself is responsible for this susceptibility because healthy blood donors have been described who are completely devoid of certain subclasses in serum. This apparent discrepancy may be partly explained by the observation that most subclass‐deficient patients have underlying aberrations in T‐cell and B‐cell interaction and function that may impair their capacity to compensate for even minor deficiencies. A prospective blind crossover study of the effect of prophylactic Ig substitution therapy was done in 43 adult patients with IgG subclass deficiency. The patients were randomized to receive 1 year of therapy with intramuscular Ig 25 mg/kg/wk or 1 year of saline injections. A significant protective effect of the prophylactic Ig therapy was seen with a great reduction in the number of days of infection. In addition, several immunologic parameters were altered after 1 year of Ig therapy. Nineteen of the patients later were included in an open study using 50 mg/kg/wk of Ig. After 6 months of treatment, significant protection against infection was observed, with a reduction of 6.2 days in the number of days per month with infection. This marked effect of prophylactic Ig suggests that the Ig aberrations seen in IgG subclass‐deficient patients contributed to their susceptibility to infection. The effect of 25 mg/kg/wk was much less pronounced than that of 50 mg/kg/wk, and normal serum IgG subclass levels were not achieved even during the higher‐dose therapy. However, it seems likely that subcutaneous or intravenous administration of larger doses of Ig would allow for more efficient therapy.

No abstract