A CD4(-1() PROLIFERATION OF LARGE GRANULAR LYMPHOCYTES EXPRESSES THE PROTEASE ACTIVATED RECEPTOR)

The platelet-type thrombin receptor was the first member to be identif ied in a family of protease activated receptors (PARs) and has been de signated PAR-1. We recently reported that the large granular lymphocyt es (LGLs) in patients with proliferations of CD8(+) cells co-expressed PAR-1 and the expression of PAR-1 correlated with the expression of C D57. Here we show, by three-colour immunofluorescence, that the LGLs f rom a patient with a rare CD4(+) CD57(+) monoclonal expansion also exp ressed PAR-1. Northern blot analysis confirmed the presence of high le vels of mRNA for PAR-1 in these LGLs.