Cutting edge: Antigen-driven lymphocyte recruitment to the lung is diminished in the absence of urokinase-type plasminogen activator (uPA) receptor, but is independent of uPA

The requirement for urokinase plasminogen activator (uPA) and uPA receptor (uPAR) in T lymphocyte migration is unknown. uPA(-/-) mice have fewer pulmo nary lymphocytes in response to certain infections, but its unknown whether this is due to diminished recruitment. Primed, recipient mice were IT inoc ulated with Ag. Three days later, fluorescently labeled lymphobIasts from b ackground-matched control wild-type (WT), uPA(-/-), or uPAR(-/-) donor mice were injected i.v., and their recruitment was determined. Approximately tw ice the number of uPA(-/-) compared with WT lymphoblasts were recruited to the lungs of WT recipients. This difference was eliminated when uPA(-/-) an d WT lymphoblasts were injected into uPA(-/-) recipients. Thus, the reduced number of lung lymphocytes in infected uPA(-/-) mice is not due to reduced recruitment. However, uPAR is critically involved in recruitment. Markedly fewer uPAR(-/-) compared with WT lymphobIasts were recruited to the lung. These findings suggest that uPAR may be a novel target for immune modulatio n in T lymphocyte-mediated disorders.