Immunological abnormalities in family members of patients with IgA nephropathy.

We examined several immunological parameters such as the number of T cells with CD4 antigen and the receptor for the Fc portion of IgA (T alpha cells), in vitro immunoglobulin production by peripheral blood lymphocytes with or without pokeweed mitogen and serum levels of immune complexes in 19 healthy family members of patients with IgA nephropathy (IgAN). It was shown that the levels of serum IgA, T4 cells, CD4/CD8 ratio of T cell subsets, T alpha cells, IgA circulating immune-complexes and spontaneous synthesis of immunoglobulins were significantly increased in family members of patients with IgAN. No family members had proteinuria or hematuria. It was concluded that immunological abnormalities, including abnormalities of T cells and B cells, were found not only in patients with IgAN but also in their healthy family members. It was suggested that some factors in addition to these immunological abnormalities may be involved in the development of IgAN.