LAK1 antigen defines two distinct subsets among human tumour infiltrating lymphocytes.

Both lymphokine activated killer (LAK) cells and specific cytotoxic T lymphocytes appear to play a role in tumour immunity. Tumour infiltrating lymphocytes (TIL) which display a CD56+ phenotype (both CD3+ and CD3-) are also likely to possess anti-tumour activity. We have previously described a 120 kDa surface antigen, termed LAK1, expressed on a subset of human peripheral blood lymphocytes (20-50%) with both NK and LAK activity. The aim of the present study was to determine whether LAK1 antigen is able to distinguish among TIL two populations of effector cells displaying either specific or non MHC-restricted (NK/LAK) activity. We showed that about 25% of freshly derived TIL were weakly stained with anti-LAK1 monoclonal antibody and most of them were also CD3+ CD56-. After culture in recombinant interleukin-2 the majority of TIL were CD3+ CD56- and the percentage of LAK1+ cells increased up to 50%. Among cloned TIL, only those lacking LAK1 antigen displayed a specific cytotoxicity against the autologous tumour, whereas the non-lytic clones were able to produce both tumour necrosis factor and gamma-interferon. Moreover, when TIL from a renal cell carcinoma were fractionated into LAK1- and LAK1+ populations, the specific lytic activity was mainly evident when LAK1- lymphocytes were used as effector cells. Conversely, LAK activity was confined to the LAK1+ subset.