IMMUNOPHENOTYPIC IDENTIFICATION OF SEZARY CELLS IN PERIPHERAL-BLOOD

Despite anecdotal literature that Sezary cells express the CD4+ CD7- i mmunophenotype, no formal validation has been published establishing t he use of this immunophenotype for clinical or experimental purposes. Consequently, the only method presently available for Sezary cell iden tification is nuclear contour analysis, a labor-intensive procedure no t generally available at most major medical centers. In this study, th e accuracy of CD4+ CD7- subset quantitation for the identification of Sezary cells was examined. The study found that the percentage of CD4 CD7- cells is elevated in many Sezary syndrome/MF patients relative t o normal, healthy individuals, In addition, CD4+ CD7-; enumeration cor relates with enumeration by nuclear contour analysis in most patients (11 of 15) with elevated CD4/CD8 ratios. The CD4+ CD7- subset also cor relates with the expression of other aberrant immunophenotypes, such a s CD3(low) or CD41(low). Lastly, CD4+ CD7- subset quantitation correla tes with the number of clonal T lymphocytes, as measured using V beta- specific T-cell receptor monoclonal antibodies. The study found this m ethod to be exceptionally accurate, with two caveats: (1) the absence of an expanded CD4+ CD7- subset in patients with a normal CD4/CD8 rati o is uninformative; and (2) in approximately 25% of patients with an e levated CD4/CD8 ratio, the Sezary cells are CD7+.