An attempt to explain disordered immunity and hypogammaglobulinemia in B-CLL.

Most CLL cases correspond to proliferation of a B-cell clone characterized by: low amounts of surface Ig (SIg); presence of receptors for mouse red blood cells; expression of a 67 Kd antigenic determinant (CD5) initially described to be a pan-T cell antigen. These peculiar characteristics differentiate the CLL B lymphocyte from B lymphocytes proliferating in other B-cell malignancies. These so-called CD5 + B cells constitute a minority of B cells in adults, although they predominate during foetal life. This latter fact induced a majority of authors to assume that CLL B lymphocytes correspond to proliferation of an immature B-cell clone. However, this hypothesis does not explain the particular high frequency with which hypogammaglobulinemia and autoimmune phenomena directed against blood cell components are found in B-CLL, as well as the difficulty to include CD5 antigen in most differentiation pathways of B-cells. In this work, we shall discuss the available evidence coming from Ly 1-B cells (mouse counterpart of CD5 B cells), indicating that these cells correspond to a separate B lineage. We shall also discuss the evidence for hypogammaglobulinemia being mainly a B cell defect caused by dilution or inhibition of normal CD5 negative B cells and disordered autoimmunity as a consequence of a disturbance of the idiotypic network, which normally antagonizes autoimmune clones.