Heterogeneous lymphokine-activated killer cell precursor populations

Abstract

We developed a monoclonal antibody (mAb) 211, which recognizes the precursors in peripheral blood of lymphokine-activated killer cells (LAK) induced by recombinant interleukin-2 (rIL-2). In conjunction with complement mAb 211 also eliminates natural killer cells (NK) and a majority of the cytotoxic T lymphocytes. B cells and monocytes do not express the 211 antigen. Since mAb 211 recognized such a large percentage of peripheral blood lymphocytes we examined which 211⁺ subpopulation was the predominant precursor of rIL-2-induced LAK cells using two-color fluoresence-activated cell sorting (fluorescein-conjugated 211 mAb plus phycoerythrin-CD11b). This method identified the 211⁺/ CD11b⁺ population as the predominant phenotype of the rIL-2-induced LAK precursor. In addition, we directly compared the phenotype of the LAK precursor induced by delectinated T-cell growth factor (TCGF) to that induced by rIL-2. The 211-depleted population, which was devoid of NK cells and LAK precursors (inducible by rIL-2), was capable of generating LAK activity when TCGF was used as the source of lymphokine. LAK cells induced by TCGF from the 211-depleted population lysed a fresh sarcoma and an NK-resistant cultured melanoma tumor target but not the Daudi cell line, which was lysed by rIL-2-induced LAK cells. Lymphoid subpopulations, depleted using NKH1a mAb, behaved similarly, generating high levels of lysis against the two solid tumor targets when cultured with TCGF but not with rIL-2. CD 3-depleted populations showed enrichment for LAK precursors using either rIL-2 or TCGF. These results indicate that while rIL-2-induced LAK precursors cannot be separated from cells with NK activity, TCGF-induced LAK cells can be generated from populations of peripheral blood mononuclear cells without NK activity.