Extracellular proteases play a crucial role in the invasive behavior of normal and transformed leukocytes. Thus far, however, most of the attention has been focused on members of the family of matrix metalloproteinases. In this work, we show that lymphoma cells can express leukocyte elastase (LE) and recruit the enzyme at their surface via ICAM-1. The expression of LE by lymphoma cells was augmented significantly by stimulation with IL-6 and IL-13, both of which also induced the expression of MMP-9. Although LE and IL-13 transcripts were detected in several non-Hodgkin's lymphomas, immunohistochemical analysis of lymphoma tissues also showed that LE was strongly expressed in infiltrating leukocytes. Given the spectrum of key molecules that can be cleaved by LE and that LE and MMP-9 are involved in the invasive behavior of normal or transformed leukocytes, our results raise the hypothesis that LE plays a crucial role in the multistep processes of inflammation and lymphoma metastasis.