Expression of multidrug resistance P-glycoprotein on peripheral blood mononuclear cells of patients with granular lymphocyte-proliferative disorders.

The immunological findings and clinical course of 33 patients with granular lymphocyte-proliferative disorders (GLPD) are presented. Based on the surface phenotypes of peripheral blood granular lymphocytes (GL), the GLPD were divided into two groups, namely CD3+ T cell-lineage GLPD (T-GLPD) and CD3- CD16+ NK cell-lineage GLPD (NK-GLPD). Twenty-one patients had T-GLPD, and 12 had NK-GLPD. One patient with T-GLPD and two patients with NK-GLPD had progressive clinical courses and died of the disease despite receiving combination chemotherapy. Among eleven patients analysed for the expression of multidrug resistance P-glycoprotein, six of eight patients with T-GLPD and all three patients with NK-GLPD clearly expressed P-glycoprotein. Since patients with immature NK-GLPD appear to undergo a progressive clinical course, we suggest that therapeutic trials using P-glycoprotein blockers in addition to chemotherapy might be beneficial for such patients.