Human antibody reacts with a B-cell subset in man to induce B-cell differentiation.

Abstract

The events leading to B-cell differentiation and maturation into plasma cells in man are still poorly defined. Human B-cell differentiation has mainly been studied after triggering by nonspecific mitogens which react with unknown B-cell-surface structures. T cells and T-cell factors play an important part in this B-cell activation1. It is therefore interesting that we found that some patients with the rare immunodeficiency disease, the Wiskott–Aldrich (WA) syndrome, possess an IgM antibody which reacts only with a subset of human B-cells from the peripheral blood and tonsils and which is able to induce B cells to differentiate into plasma cells in vitro. This triggering is largely independent of T cells and in certain conditions occurs in the absence of detectable B-cell proliferation. In view of certain recent findings in some immunologically defective strains of mice such as CBA/N, genetic immunodeficiencies in man may represent useful models for investigating human B-cell subsets and the process of B-cell activation. We have therefore looked for B-cell antibodies in the serum of WA patients because, in addition to an immune defect of poorly understood mechanism2, these patients have major thrombocytopenia and are therefore multi-transfused. We found that the serum of seven of nine W A patients contained an antibody reacting by cytotoxicity and immunofluorescence tests with a subset of both normal human and, unexpectedly, of the patients' own B cells.