Lymphocyte subpopulations in the neonate: Identification of an immature subset of OKT8-positive, OKT3-negative cells

T cell subpopulations of lymphocytes from cord blood (CBL) of 24 newborns and from peripheral blood (a-PBL) of 24 healthy adult volunteers were assessed in T cell-enriched, T cell depleted and unseparated lymphocyte fractions by using OKT3, 4, 6, and 8 monoclonal antibodies. The results show that T cell-enriched CBL include adult numbers of OKT3 ⁺, OKT4 ⁺, OKT6 ⁺ and OKT8 ⁺ lymphocytes whereas the T cell-depleted fraction consists of a high percentage of OKT8 ⁺, OKT3 ^-, non-E rosette-forming cells bearing a PNA receptor. The presence of the PNA receptor and the lack of the OKT3 ⁺ antigen strongly support the hypothesis that the subset of OKT8 ⁺ cells in cord blood includes immature T lymphocytes that may represent an intermediate stage between thymocytes and mature peripheral T cells.