Selective IgA deficiency and circulating immune complexes containing bovine proteins in a child with chronic graft versus host disease.

We have previously shown that a selective absence of serum and secretory immunoglobulin A (IgA) may lead to the development of circulating immune complexes which appear to contain bovine milk antigens. We report here that high levels of circulating immune complexes were found in the serum of a child who was treated for severe combined immunodeficiency by bone marrow transplantation but in whom the IgA-producing cells subsequently failed. As increasing amounts of complexes appeared over a two year period, the child had a parallel progression of an apparent chronic graft versus host disease including a Sjögrens syndrome and scleroderma. Very large amounts of complexes were eventually formed but the level fell 77 per cent after milk was excluded from the diet. Chemical studies on the complexes showed that the majority of complexes did contain bovine milk proteins, and fluorescence antibody staining of skin biopsy samples showed the presence of dense deposits of bovine casein in the dermis. The relationship between bovine protein-antigen antibody complexes and the chronic graft reaction remains uncertain.