The purpose of this study was to evaluate the binding of a panel of monoclonal antibodies to human pre-B cells present in fetal, pediatric, and adult bone marrow. The antibodies included BA-1, BA-2, BA-3 (anti-CALLA), anti-B1, L243 (anti-HLA-DR), and T101. Binding of the monoclonal antibodies to pre-B cells was evaluated at the single-cell level by double fluorochrome analysis. Percentages of BA-1+ and anti-B1+ pre-B cells were independent of age group. BA-1 bound to approximately 80% of fetal, pediatric, and adult bone marrow pre-B cells, whereas anti-B1 bound to approximately 50%. BA-2 bound to 55% of fetal pre-B cells, but this percentage decreased to 32% in pediatric and 16% in adult bone marrow. CALLA was expressed on less than 10% of fetal, pediatric, and adult bone marrow pre-B cells, and HLA-DR was expressed on greater than 95% of fetal, pediatric, and adult pre-B cells. Although T101 (an anti-T-cell monoclonal antibody) did not bind to pre-B cells, it did bind to approximately 25% of the sIgM+ cells in fetal bone marrow. These results suggest a predominant phenotype of L243 (anti-HLA-DR)+, BA-1+, BA-3 (anti-CALLA)-, T101- for the human pre-B cell while phenotypic heterogeneity exists for anti-B1 and BA-2.

A 2.5-yr-old girl was evaluated for seizurelike episodes and psychomotor and growth retardation. Cytogenetic study showed a ring 14 chromosome in most cells, with some cells having monosomy 14. Rarely, a cell showed a double ring chromosome 14. Both parents had normal chromosomes. Because serum immunoglobulins have been mapped to the distal portion of 14q, we attempted to correlate Ig levels with the deletion involved in the formation of this ring. No decrease in IgG, IgM, IgA, IgE, and IgD serum levels was observed. The normal serum Ig levels found in the proposita are compatible with the suggestion that the Ig loci are not located on the terminal portion of 14q but more proximally in band 14q32. However, because Gm and Am allotyping was not available mapping was not conclusive.