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 gamma delta 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.