In vitro development of lymphocytes that function as progenitors for mucus-secreting lymphokine-activated killer (LAK) cells.

Abstract

Two different types of cultures developed when two different interleukin 2 (IL-2) preparations were introduced into cultures of lymph node cells of nu/nu (nude) mice maintained on an embryonic fibroblast monolayer. In the first, human recombinant IL-2 (rIL-2) stimulated the generation of colonies of large cytotoxic cells identified as lymphokine-activated killer (LAK) cells that, when grown on mesenchyme fibroblastoid monolayers prepared from 16- to 18-day embryos, could be triggered to synthesize and secrete flowing mucoid material. In the second culture, crude supernatant from cultures of rat spleen cells stimulated by concanavalin A stimulated the appearance and multiplication of blast cells that, after 20 days, differentiated into lymphocytes. This population was homogeneously composed of "wandering" lymphocytes and could be kept in a stable resting form for at least 2 months without loss of viability. When exposed to rIL-2, this whole lymphocyte population underwent a transformation into blast cells that, on the fourth day, generated granules, became cytotoxic, and differentiated into granular mucus-secreting LAK cells. When low numbers of these transformed premitotic blast cells were plated on mitomycin C-treated embryonic fibroblast monolayers, one cell out of 15 to 20 generated a clone of LAK cells. The study demonstrates that both effector and "memory" arms of differentiation can be stimulated in vitro.