The relationship of HNK-1 (Leu 7) and VEP13 antigens on human cells mediating natural killing.

The NK cell associated antigens defined by the two monoclonal antibodies, HNK-1 (anti-Leu 7) and VEP13, were investigated for their mutual expression on peripheral blood lymphocytes of healthy donors. In double labelling experiments only 6 +/- 3.9% of peripheral blood lymphocytes (PBL) were found to carry both markers. When VEP13+ cells were enriched by rosette formation using VEP13 coated ox red blood cells all the NK activity was recovered in the VEP13+ cell preparation, whereas the VEP13- subset was devoid of it, despite of the fact that there was a remainder (7-13%) of HNK-1+ cells. These VEP13- HNK-1+ cells were found to also bear the T3 antigen but lack the M1 antigen. Thirty-eight to sixty-eight per cent of VEP13+ enriched cell population expressed the HNK-1 antigen too. When these cells were further separated into HNK-1+ and HNK-1- cells by means of the FACS thus yielding the VEP13+ HNK-1+ and VEP13+HNK-1- subsets, it could be demonstrated that both populations were able to mediate natural killing against K-562 target cells thus indicating existence of an HNK-1- natural killer cell population. Investigating lymphocytes from a patient suffering from a leukaemia in which 75% of cells were of LGL morphology, 32% of cells were found to be HNK-1+ while 76% of cells were shown to bear the VEP13 antigen, thus revealing a similar phenotype as observed in normal individuals. Our results indicate the existence of a HNK-1- VEP13+ natural killer cell population.