Selectins are attractive targets for specific anti-inflammatory therapies. Using human lymphocytes as well as an L-selectin-transfected pre-B-cell line in dynamic flow chamber experiments, we could demonstrate that the small-molecule compound efomycine M blocks L-selectin-mediated lymphocyte rolling on sialylated Lewis(X), an action that was confirmed by plasmon resonance spectroscopy. Recruitment of naive lymphocytes to peripheral lymph nodes depends on L-selectin-mediated adhesion to high endothelial venules. We performed intravital microscopy studying lymphocyte rolling in peripheral lymph nodes and showed a 53% reduction (P=0.0006) of lymphocyte rolling in mice treated with efomycine M or a function-blocking antibody against L-selectin. In addition, the number of lymph node-homing T cells was reduced by >60% using either efomycine M or L-selectin-blocking antibodies. As recruitment of naive lymphocytes is a prerequisite for sensitization in T-cell-mediated immune reactions and allergic responses, mice were treated with efomycine M or an L-selectin-specific antibody during contact sensitization with DNFB. After adoptive transfer of corresponding T cells into non-sensitized recipient mice, the capacity of these cells to induce contact hypersensitivity was significantly reduced (P=0.0002 and P=0.0001, respectively). Our data demonstrate that it is possible, in principle, to diminish T-cell-mediated allergic reactions through interference with L-selectin functions during the early sensitization phase.