Possible Role of Interleukin‐10 in Autoantibody Production and in the Fate of Human Cord Blood CD5+ B Lymphocytes

Mononuclear cell subsets in 25 human umbilical cord blood samples and 10 healthy adults were studied. We found a decreased percentage of CD3+ cells, CD8+ cells and gammadelta T cells in cord blood compared with blood from healthy adults. The CD16+56+ and CD19+CD5+ phenotypes were overexpressed in cord blood. We then measured spontaneous gene expression and the production of interleukin-10 in mononuclear cells from cord blood and adult subjects. Although we found no difference between cord blood cells and those from healthy adults, a tendency towards spontaneous interleukin-10 production was observed in cord blood. Phorbol 12-myristate 13-acetate stimulation revealed that, among lymphocytes, cord blood B cells are the main cellular source of interleukin-10. Finally, we found no evidence of augmented spontaneous apoptosis but an increased bcl-2 gene expression in non-T cells from cord blood. Interleukin-10 might protect CD19+CD5+ B cells from apoptosis by inducing bcl-2 and promoting autoantibody production in this B-cell subpopulation.