Immunophenotypic characterisation of cord blood B-lymphocytes

The phenotypic analysis of human umbilical cord blood (CB) mononuclear cell s is important to study their maturity and differentiation regarding their transplantable capacity. In this work we have studied differential expressi on of B cell antigens on CDS-/HLA-DR+ B cells (B1b, B2) and CD5+/HLA-DR+ ce lls (Bla) from the CB (n=6) and adult peripheral blood (PB) (N=6). CDS-PE, HLA-DR-PerCP and FITC labelled anti-B cell MoAb panel of the 6(th) Internat ional Workshop on Human Differentiation Antigens were used for detection of B cell subpopulations. FacsCalibur (B-D) flow cytometer was used for evalu ation of samples. CB Bla (CD5/HLA-DR++) cells proved to be positive with CD 9, CD19, CD20, CD21, CD22, CD23, CD24, CD32, CD39, CD45RA, CD76, CD79, MHC- II, IgM and anti Ig light chains MoAbs. CB Bib (CD5-/HLA-DR+) cells reacted with CD9, CD19, CD20, CD21, CD22, CD23, CD24, CD32, CD39, CD45RA, CD79, MH C-H, and IgM MoAbs. PB B cells (B2) expressed CD19, CD20, CD21, CD22, CD24, CD32, CD37, CD39, MHC-II and CD79 Ags. Unlike to the PB the CB B lymphocyt es proved to be predominantly B1 cells representing a new-born B cell reper toire. Besides expressing many B cell antigens both the CB Bla and Bib cell s showed CD9+, CD45RA+, IgM+ immature, "naive" B cell phenotype. Functional ly, B1 cells are capable producing polyreactive IgM and natural autoantibod ies but not IgG. This antibody profile might be insufficient regarding the recipient humoral immune defense result in more severe immunodeficiency aft er CB transplantation.