Effect of recombinant human interleukin 2 (rIL-2) on normal peripheral blood B cells and B lymphoblastoid cell lines

The role of interleukin 2 (IL-2) for growth and differentiation of normal and malignant B cells still remains controversial. We assessed normal peripheral blood B cells and cell lines derived from patients with B non-Hodgkin's lymphomas (NHLs) with respect to their responsiveness to recombinant human IL-2 (rIL-2). The NHL cell lines used in our experiments expressed the Tac antigen (CD25)--a compound of the IL-2 receptor (IL-2R)--in a percentage ranging from 28 to 57%. As measured in a [3H]thymidine uptake assay, the normal peripheral blood B cells demonstrated a dose-dependent proliferative response to rIL-2, whereas the NHL cells did not show any responsiveness to rIL-2. In a clonogenic culture assay we evaluated the colony formation of the NHL cells and found a decrease of 28 to 41% on average in the presence of rIL-2 (10-50 U/ml). This moderate inhibitory effect on the clonal growth of the NHL cells was not due to a differentiation inducing effect of rIL-2, as studied by measuring the Ig production under increasing doses of rIL-2 (1 to 100 U/ml). Thus, malignant NHL B cells may express the CD25 compound of the IL-2 receptor on their surface, demonstrating a different functional responsiveness to rIL-2 compared to normal peripheral blood B cells.