Clinical application of a rapid, functional assay for multidrug resistance based on accumulation of the fluorescent dye, fluo-3

A rapid and simple functional assay for P-glycoprotein (Pgp) using flow cytometry to measure the accumulation of the flurophore fluo-3 has been applied to samples from patients with B-cell chronic lymphocytic leukaemia (B-CLL). Peripheral blood lymphocytes from 37 patients with B-CLL were studied for Pgp. Pgp expression, using MRK-16, a monoclonal antibody recognising an external surface epitope of Pgp, was detected in 92% of patients with B-CLL. The functional assays for Pgp expression were positive in 78 and 59% of patients using the fluo-3 and doxorubicin (dox) assays, respectively. When compared with the MRK-16 assay, the fluo-3 assay had a sensitivity of 82% compared to a sensitivity of 56% for the dox assay (P = 0.004). The specificity of the fluo-3 and dox assays could not be evaluated because of the low number of MRK-16 negative CLL cells.

Autoreactive platelet antibody in post transfusion purpura

Post transfusion purpura in a DR3, DRw52 positive, PlA1 negative woman rapidly responded to high-dose intravenous gammaglobulin therapy. Using the platelet immunofluorescence test (PIFT) high titre IgG and IgM alloantibodies were detected in the patient's acute serum. These alloantibodies had PlA1 specificity and the patient's serum produced a broad, 100 kDa band on Western Blot with PlA1 positive platelets. Acute phase serum also contained an IgG antibody which reacted in the PIFT with the patient's own platelets, and PlA1 negative platelets. When tested by Western Blot with PlA1 negative and Glanzmann's Thrombasthenia platelets, the acute serum produced bands at 180 and 200 kDa. The autoreactive antibody was not detected once the platelet count returned to normal. These findings provide evidence for the hypothesis that the mechanism of autologous platelet destruction in PTP is autoimmune.

Lesch-Nyhan syndrome: evidence for abnormal adrenergic function

Subjects with the Lesch-Nyhan syndrome (hypoxanthine-guanine phosphoribosyltransferase deficiency with self-mutilation) exhibit an apparently unique pattern of adrenergic dysfunction characterized by elevated plasma dopamine beta-hydroxylase activity and an absence of pressor response to acute sympathetic stimulation. Patients with a partial deficiency of hypoxanthine-guanine phosphoribosyltransferase without self-mutilation do not exhibit these abnormalities of adrenergic function.