title: Phenotypic features and proliferative activity of B cell progenitors in X-linked agammaglobulinemia.
abstract: In this study, we applied mAb and heterologous antisera in double marker combinations to investigate the phenotype and the proliferative activity of immature B lineage cells in XLA. Bone marrow (BM) samples from eight male adult patients with no circulating B lymphocytes were studied. The proportions and the phenotype of the earliest identifiable B cell progenitors, expressing nuclear terminal deoxynucleotidyl transferase (TdT), cytoplasmic CD22, and membrane CD19 and CD10 were identical to those observed in normal BM. In XLA these cells represented 1.2% to 22% of BM mononuclear cells; 5% to 42% and 1% to 45% of such cells weakly expressed CD20 and CD37, respectively, and invariably lacked CD13 and CD33. Cytoplasmic mu+ sIg- pre-B cells were seen in low numbers (0.1% to 0.3%) in four samples and were undetectable in the remaining four. Consequently, the ratio TdT+/c mu+ was greater than 100 in five out of eight samples studied in contrast to the less than 10 values seen in normal individuals. The proliferative activity of B lineage progenitor cells was studied by using Ki67 and anti-bromodeoxyuridine mAb. Although the proliferation of TdT+ cells in XLA was comparable with that seen in normal BM samples (24% to 59% of TdT+ were Ki67+ and 11% to 27% incorporated bromodeoxyuridine), this was dramatically reduced in the c mu+ cells (no c mu+, Ki67+ seen in three samples where pre-B cells were observed). Thus, the abnormalities of B cell differentiation in XLA are first seen at the c mu+ pre-B stage and suggest a maturation block in the transition between TdT+, c mu- pre-pre-B cells and c mu+ pre-B cells. The severity of this block may be variable, allowing the generation of a near normal number of pre-B cells in some patients, which nevertheless have a defective proliferative activity. Finally, our study further supports the concept that the effects of the "XLA gene" are confined within the B lineage by demonstrating that the proportions of T cells bearing TCR-alpha beta and TCR-gamma delta in XLA are similar to those seen in normal individuals.
authors.affiliation: Department of Immunology, Royal Free Hospital School of Medicine, London, U.K.
authors.forename: D
authors.initials: D
authors.lastname: Campana
authors.forename: J
authors.initials: J
authors.lastname: Farrant
authors.forename: N
authors.initials: N
authors.lastname: Inamdar
authors.forename: A D
authors.initials: AD
authors.lastname: Webster
authors.forename: G
authors.initials: G
authors.lastname: Janossy
mesh_terms: D000361:Agammaglobulinemia / Q000503:physiopathology*; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000032:analysis; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D001402:B-Lymphocytes / Q000502:physiology*; D001854:Bone Marrow Cells; D002454:Cell Differentiation; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism; D006410:Hematopoiesis; D006801:Humans; D008213:Lymphocyte Activation; D008297:Male; D011948:Receptors, Antigen, T-Cell / Q000032:analysis; D014960:X Chromosome
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D011948:Receptors, Antigen, T-Cell; D004253:DNA Nucleotidylexotransferase