Characterization of human granular lymphocyte subpopulations expressing HNK‐1 (Leu‐7) and Leu‐11 antigens in the blood and lymphoid tissues from fetuses, neonates and adults

Three subpopulations of human granular lymphocytes from blood and lymphoid tissues were characterized using combinations of the monoclonal antibodies (mAb) HNK‐1 (Leu‐7), Leu‐11 and VEP13. Each subpopulation was confirmed to possess natural killer (NK) cell functional capability, but a different level of cytotoxic efficiency (HNK‐1⁺Leu‐11⁻ HNK‐1⁺Leu‐11⁺ < HNK‐1⁺Leu‐11⁺). In adult from 23 healthy donors, the subpopulations with HNK‐1⁺Leu‐11⁻, HNK‐1⁺Leu‐11⁺ and HNK‐1⁺Leu‐11⁺ phenotypes comprised 4.7 ± 3.0, 8.0 ± 6.4 and 3.9 ± 3.5% of mono‐nuclear cells, respectively. Despite their distinct surface marker phenotypes and NK functional ability, all 3 subpopulations exhibited granular lymphocyte morphology. One of these subpopulations, HNK‐1⁺Leu‐11⁻, also expressed the pan‐T cell antigen Leu‐4. Different patterns were observed in fetal bone marrow and cord blood, where the vast majority of HNK‐1⁺ cells lacked the Leu‐11 antigen (HNK‐1⁺ Leu‐11⁻ cells). The HNK‐1 antigen was not expressed on granulocytes and their precursors, whereas both Leu‐11 and VEP13 antigens were expressed on these myeloid cells from fetal bone marrow and cord blood as well as adult bone marrow and spleen. Cell lines of granular lymphocytes cultured in the presence of interleukin 2 all possessed the HNK‐1⁺Leu‐4⁺ phenotype and NK functional capability but lacked the Leu‐11 and VEP13 antigens on their surface after 15 days of culture. Although granular lymphocytes expressing the Fc receptors reacting with the mAb Leu‐11 and VEP13, are the most functionally active NK cells, the HNK‐1⁺ subpopulation lacking the Leu‐11 and VEP13 antigens appears to be an important population (possibly an immature form of granular lymphocytes) for delineating the cell lineage(s) and differentiation of human granular lymphocytes. Although none of the currently available mAb react both inclusively and exclusively with human granular lymphocytes, the combination usage of these antibodies permits a more precise and comprehensive analysis of these subsets.