Lymphocyte subpopulations in the neonate: High percentage of circulating B73.1⁺, HNK-1^- cells

The reactivity of B73.1 monoclonal antibody was evaluated on unseparated and on T cell-depleted and T cell-enriched fractions of both cord blood lymphocytes (CBL) and adult peripheral blood lymphocytes (a-PBL). The reactivity of this monoclonal antibody with the E^-, OKT3^-, OKT8⁺, HNK-1^- subset of CBL, previously demonstrated to have NK activity, was also studied. The data show that B73.1⁺ cells were present in similar percentage in CBL and a-PBL while HNK-1⁺ cells were very low in CBL. In addition the B73.1 monoclonal antibody reacted with about 50% of the E^-, OKT3^-, OKT8⁺, HNK-1^- CBL and within this subset the majority of the B73.1⁺ cells were PNA^-. These data support the hypothesis that part of this neonatal subpopulation, belongs to the NK cell lineage. Moreover the results obtained by double-labelling with B73.1 monoclonal antibody and PNA suggest that the E^-, OKT3^-, OKT8⁺, HNK-1^- CBL include either different subsets or various differentiation stages of the same subset.