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Clin Exp Immunol. 1991 Jun;84(3):389-94.

Are cord blood B cells functionally mature?

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  • 1Department of Medicine, Geneva University Hospital, Switzerland.


Very low immunoglobulin secretion occurs in pokeweed mitogen (PWM) stimulated cord blood mononuclear cells (MNC) and has been attributed to an 'immaturity' of both T and B cells of the newborn. The cord blood T cells are phenotypically 'naive' cells, in which suppressor activity for B cell function appears to dominate over helper activity. The cord blood B cells, in spite of their expression of different membrane immunoglobulin isotypes, secrete almost no IgG and IgA in the various B cell assays so far compared. We found that cord blood B cells are as competent as B cells from adults to generate clonal IgM, IgG and IgA responses in a culture system in which a cell contact with mutant EL-4 thymoma cells in conjunction with T cell supernatant leads to strong B cell activity. As regarding the possible causes of the low cord blood PWM response, we studied the role of transforming growth factor-beta 1 (TGF-beta 1), a potent inhibitor of lymphocyte functions. TGF-beta 1 sensitivity of B cells and TGF-beta 1 mRNA levels in MNC were found to be similar for adult and cord blood cells. A neutralizing anti-TGF-beta 1 antibody enhance the adult PWM response, but the immunoglobulin secretion in cord MNC remained very low. We conclude that suppression by endogenous TGF-beta 1 occurs in the PWM system but is not responsible for the low immunoglobulin response of cord blood MNC and that the newborn's B cell 'immaturity' can be overcome with potent T cell signals in vitro. This is consistent with the newborn's capacity to generate a T-dependent B cell response in vivo.

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