Leucoagglutinin induces differential proliferation of lymphocyte subsets

Abstract

In this study we have established culture conditions that allow the preferential and rapid expansion of either T cell receptor (TCR)⁺/CD3⁺16⁻ T lymphocytes or TCR⁻/CD3⁻16⁻ natural killer (NK) cells, or the non-selective outgrowth of both subsets. Optimal proliferation of lymphocytes was obtained using a combination of irradiated allogeneic peripheral blood lymphocytes (PBL) and irradiated Epstein Barr virus (EBV) transformed lymphoblastoid B cell lines (B-LCL). Addition of 1μg/ml leucoagglutinin to the culture medium induced a preferential outgrowth of TCR⁻/CD3⁻16⁻ T lymphocytes. The proportion of TCR⁻/CD3⁻16⁻ NK cells was decreased to 5% or less, although still a 2000-fold multiplication of TCR⁻/CD3⁻16⁻ NK cells was obtained at day 13. Without leucoagglutinin a 1000-fold increase of about 70% pure TCR⁻/CD3⁻16⁻ NK cells was obtained at day 13. Intermediate concentrations of leucoagglutinin (0.1–0.3μg/ml) resulted in a non-selective expansion of both NK cells and T cells. Irrespective whether leucoagglutinin was added or not, the number of TCR⁺/CD3⁺8⁺ lymphocytes increased more rapidly relative to the TCR⁺/CD3⁺4⁺ lymphocytes resulting in an increased TCR⁺/CD3⁺8⁺ population size.

Also under limiting dilution conditions leucoagglutinin increased the frequency of proliferating cells. In contrast to the preferential outgrowth of TCR⁺/CD3⁺8⁺ lymphocytes in bulk cultures, approximately 80% of the clones generated was TCR⁺/CD3⁺4⁺, demonstrating a growth promoting effect of TCR⁺/CD3⁺4⁺ lymphocytes on TCR⁺/CD3⁺8⁺ lymphocytes in PBL bulk cultures.