FUNCTIONAL ASSESSMENT OF A B-CELL DEFECT IN PATIENTS WITH SELECTIVE IGA DEFICIENCY

  • 1 January 1979
    • journal article
    • research article
    • Vol. 35  (2) , 296-305
Abstract
The cellular basis of selective Ig[immunoglobulin]A deficiency was investigated by examining the terminal differentiation of B [bone marrow-derived] lymphocytes co-cultured with varying ratios of T [thymus-derived] lymphocytes in presence of pokeweed mitogen. Patients (8) were studied who had serum IgA concentrations < 0.05 mg/ml, salivary IgA < 0.01 mg/ml and 0.8-4% lymphocytes with surface IgA markers. Peripheral blood lymphocytes from patients and normal donors were separated into B cell (non-T cell) and T cell fractions by E[erythrocyte]-rosetting. Microcultures were established at 11 B cell to T cell ratios from 100% B cells to 100% T cells. After 7 days, Ig in the supernatant fluid was measured by radioimmunoassay. Cultures containing patients'' B cells and autologous or allogeneic T cells produced very low or undetectable amounts of IgA. Cultures from 6 of 8 patients contained cells with intracytoplasmic IgA. Secretion of IgM by the patients'' B cells was identical to that of normal donors. IgG production by patients'' B cells was less than that produced by normal B cells especially in the mid-range ratios of the microcultures. Production of IgA, IgG and IgM by normal B cells from peripheral blood or tonsils was very similar in the presence of normal T cells or patients'' T cells. In cultures containing optimal ratios of normal B cells, the patients'' T cells did not suppress IgA production and gave normal help for IgA production. A defect in patients with selective IgA deficiency was the functional inability of their B cells to produce normal amounts of IgA in vitro even when provided with normal allogeneic T cell help.