Differential effects of a murine and chimeric mouse/human anti-interleukin-2 receptor antibody on human T-cell proliferation.

The preference for interleukin-2 receptor (IL-2R) expression on activated, compared with resting T lymphocytes makes the IL-2R a promising target for selective immunosuppressive therapy. To increase the potential therapeutic effectiveness of anti-IL-2R monoclonals, a chimeric mouse/human variant was constructed from Ig genes isolated from a murine anti-human IL-2R hybridoma cell line, designated AHT54. AHT54 binds to the same or spatially related epitope as IL-2 on the p55 protein that constitutes the low- and high-affinity forms of IL-2R. Although the murine and chimeric AHT54 antibodies inhibited cell-surface binding of IL-2 to the same extent, the chimeric antibodies containing a human IgG1 constant region had substantially more anti-proliferative activity than their murine IgG1 counterparts. Our results indicated that the human constant region of the chimeric antibodies interacted more efficiently than the murine constant region with effector components present in peripheral blood mononuclear cells (PBMC).