Pre‐B Cells and B Lymphocytes in Human Cord Blood and Adult Peripheral Blood

The frequencies of pre‐B cells and B lymphocytes subpopulations were studied in 43 cord blood and 21 adult peripheral blood samples using a direct immunofluorescence double staining method. We found pre‐B cells in 40 out of 43 cord blood samples studied, a rate of 93%, and in 16 of 21 adult blood samples, a rate of 76%. The mean frequency of pre‐B cells in cord blood lymphocytes was 0.7%, while that in adult blood lymphocytes was 0.2%. The pre‐B cells in both groups were all small pre‐B cells. The mean frequency of B lymphocytes in cord blood was 11.4%, higher than that in adult blood (5.4%). The difference in B lymphocyte frequency between cord blood and adult blood was exclusively due to high frequency of surface IgM‐positive and IgD‐positive B lymphocytes in the cord blood.