An Explanation for the Heterogeneity in B Lymphocyte Ecto-5′-Nucleotidase Activity in Patients with Hypogammaglobulinemia

Abstract

A deficiency of lymphocyte ecto-5′-nucleotidase (ecto-5′-NT) ¹ activity in patients with common variable immunodeficiency (CVI), congenital X-linked agammaglobulinemia (CAG), severe combined immunodeficiency (SCID), and a variety of other immunodeficiency diseases is well described (1-6). Adult peripheral B cells have three- to five-fold higher ecto-5′-NT activity than peripheral T cells (3). Thus, any disease which causes a loss of surface immunoglobulin-positive (slg+) B cells from the peripheral blood, such as CAG, will cause a decrease in total lymphocyte ecto-5′-NT activity (3). Ecto-5′-NT deficiency may also be caused by decreased enzyme activity in T cells, B cells, or both (1,3,4). We have previously shown that decreased ecto-5′-NT activity in T cells of patients with CVI and CAG is due to decreased numbers of ecto-5′-NT+ cells from both the helper (0KT4-) and suppressor (0KT8+) subpopulations (4). Furthermore, increased percentages of ecto-5′-NT^- T cells in these patients appears to be correlated with an increased capacity for the suppression of pokeweed mitogen (PWM) driven immunoglobulin synthesis in vitro. Ecto-5′-NT- maternally engrafted T cells in a patient with SCID and maternal graft versus host disease also suppressed PWM-driven immunoglobulin synthesis (6). Thus, T cell ecto-5′-NT deficiency does not necessarily indicate T cell immaturity.