Abnormalities of IgA specific B cell and suppressor T cell functions in a patient with selective IgA deficiency and systemic lupus erythematosus

Selective IgA dificiency can be detected about 0.006% of the population of blood donors in Japan. The deficiency can often be associated with autoimmune disorders. We have examined in vitro immunoglobulin synthesis in a SLE patient with IgA deficiency. The patient, a female aged 31, had high fever and polyarthralgia at the age of 20-year-old and since then she has been taking medicine at intervals. During this period, she has been suffered from tonsillitis, appendicitis, otitis media and pneumonia. The patient was hospitalized under the diagnosis of SLE. The quantitative immunoglobulin levels were IgG 2190, IgA 0, IgM 269 (mg/dl). Peripheral lymphocyte counts were normal and T: B ratio was 65: 35. Immunofluorescent examination revealed that Ig bearing cells were present in normal number on peripheral blood smear. Immunoglobulin biosynthesis in the patient's peripheral blood lymphocytes was measured in vitro. As a consequence, IgG and IgM were synthesized at a normal level, but IgA at an extremely low rate. Coculture of T cells from normal and B cells from the patient resulted in reduced synthesis of IgA, and moreover combination of the patient T cells and normal B cells also resulted in reduced synthesis of IgA. However co-culture of X-ray irradiated T cells from the patient and B cells from normal resulted in sufficient production of IgA. Thus, pathogenesis of IgA deficiency in the patient was demonstrated to be due to B cell insufficiency and hyperfunction of suppressor T cells.