Extravascular natural cytotoxicity in man: Anti-K562 activity of lymph-node and tumour-infiltrating lymphocytes.

A major distinction is reported between the cytolytic activity of peripheral blood lymphocytes (PBL) and that of lymph-node and tumour-infiltrating lymphocytes (TIL) against targets of the NK-sensitive K562 cell line in short-term 51Cr release assays. In the PBL of normal donors and lung cancer patients in whom disease was advanced anti-K562 reactivity, though variable, was consistently detectable and this activity could be augmented to a similar extent in patients and controls by treatment of effectors with exogenous interferon (IF). By contrast anti-K562 activity in lymph-node cells (LNC) and TIL was virtually absent and significant levels could not be induced by exposure to IF. This activity was not attributable to coexistent suppressor cells for NK function since admixture of LNC and TIL with normal PBL failed to modulate K562 killing by the latter. The results imply that K562-reactive NK cells and their precursors may frequently be present at sub-threshold levels in the lymph nodes of tumour-bearing patients and a similar explanation could account for the inactivity of TIL. However, in the latter situation, actively-induced NK dysfunction in situ incapable of regeneration by IF, and attributable to as yet undefined tumour-associated factors, may also be involved.