Infiltration patterns of short- and long-term cultured A-NK and T-LAK cells following adoptive immunotherapy.

Direct contact between lymphokine-activated killer (LAK) cells and tumour cells is believed to be imperative for initiating tumour cell lysis in vitro as well as in vivo. In order to optimize adoptive immunotherapy (AIT) it is therefore desirable to identify the LAK cell subtype, which ensures maximal infiltration of tumours as well as a substantial cytotoxic reactivity. In this report we have compared short- and long-term cultured murine adherent natural killer (A-NK) cells and mitogen-stimulated, lymphokine-activated T-killer (T-LAK) cells with respect to their proliferative potential, cytotoxicity, requirement for interleukin-2 (IL-2) and ability to infiltrate B16 pulmonary metastases following adoptive transfer. We found that short-term (5 days) cultured A-NK and T-LAK cells both showed a substantial accumulation of tumour tissues. However, A-NK cells gradually lost this ability during in vitro culture whereas T-LAK cells cultured for as long as 20 days retained their ability to infiltrate metastases as efficiently as their short-term cultured counterparts. Moreover, the low requirement of IL-2 by T-LAK cells to achieve maximal infiltration of tumours sharply contrasted with the excessive doses necessary to ensure maximal infiltration by A-NK cells. In conclusion, these data demonstrate that short-term cultured LAK cells of both NK- and T-cell origin are able to infiltrate B16 pulmonary metastases effectively. Importantly, the T cells retain this ability for a considerably longer time and require much less IL-2 support than do A-NK cells, making T-LAK cells attractive for AIT.