Correlation of immunoregulatory function with cell phenotype in cord blood lymphocytes

The strong suppressor activity of cord T lymphocytes contrasts markedly with their mainly CD4 (helper) rather than CD8 (suppressor) phenotype. We studied the phenotype of cord CD3, CD4 and CD8 cells compared to adult cells using the monoclonal antibodies, 2H4, 4B4, and UCHL1. Almost all cord CD4 lymphocytes carried the suppressor-inducer marker 2H4, whereas 4B4+ UCHL1+ helper-inducer cells were virtually absent; CD8 cord cells were also of the 2H4+ 4B4- UCHL1- phenotype. In contrast in adult peripheral blood, half of the T cells, whether CD4 or CD8, were 2H4+ and half 4B4/UCHL1+. The suppressor-inducer phenotype of cord T cells was shown, in parallel functional experiments, to correlate with their enhanced proliferation to lectin and poor production of immunoglobulin and with the ability of cord mononuclear cells to suppress proliferation and immunoglobulin production by adult cells in co-culture experiments. These results indicate that the major imbalance in the cord CD4 subset in favour of 2H4 cells can explain many of the functional differences from adult cells. However, involvement of other cell types, in particular of the monocyte lineage, is necessary to explain other properties of immunocompetent cord cells.