IgA deficiency in children. Immunoglobulin-containing cells in the intestinal mucosa, immunoglobulins in secretions and serum IgA levels.

Twenty-eight children with IgA deficiency were investigated by studying immunoglobulin-containing cells in the jejunal and rectal mucosa by direct immunofluorescence and by measuring immunoglobulins in the intestinal juice and saliva. Serum IgA was measured by radioactive single radial immunodiffusion. IgM-containing cells were predominant in all biopsy specimens. Their number was not altered in three coeliac patients. The number of IgG-containing cells was elevated in the jejunal, but not in the rectal mucosa. The number of IgE-containing cells was not altered. Staining of the intestinal structures with anti-IgM serum had the same characteristics as observed with anti-IgA in normal children. IgM predominated in the intestinal juice. The salivary content of IgM was higher than in the controls, but it was surpassed by IgG. Traces of IgA were detected in the sera of eighteen patients. Most of these had a few IgA-containing cells in the intestinal mucosa and some had IgA in secretions. The study indicates that the deficient IgA is quantitatively replaced by IgM in the intestine of children with IgA deficiency. IgM in the intestine of IgA-deficient children has characteristics in common with IgA in normal children.