Human lymphokine-activated killer cells develop syngeneic killing ability.

Lymphokine-activated killer (LAK)-cell therapy has emerged as a new strategy in designing protocols for the treatment of cancer. However, in its present clinical form, it has not fulfilled the early promise shown in murine models of human metastatic disease. In an attempt to gain understanding as to why this might be the case, we measured the ability of human LAK cells, generated in vitro for 4 days, to kill LAK cells from the same donor that had been exposed to IL-2 in vitro for 8 days, and vice versa. In eight separate experiments using different donors, 4-day ('early') LAK cells were able to kill syngeneic 8-day ('late') LAK cells, while late LAK cells were also able to kill early LAK cells. Strong killing was observed in both directions, which was almost total in one instance. In order to assess the development of this phenomenon, early LAK cells were tested for their ability to kill syngeneic LAK cells that were 1, 2, 3 or 4 days 'older' and the reciprocal experiment conducted using late LAK cells as effectors. The results illustrate a strong capacity for the development of syngeneic killing by human LAK cells. The possible implications of this phenomenon for the clinical administration of LAK cell/IL-2 therapy are discussed.