In this study, we have evaluated 14 large granular lymphocyte (LGL) expansions, 11 of which were CD8+. Analysis of the membrane expression of the α and β chains of the CD8 antigen, using specific monoclonal antibodies (MoAbs), has shown that LGL expansions with the CD3+, CD4+, CD8+, CD57+ T-cell receptor (TcR) αβ phenotype bear the CD8α/α isoform, while the CD3+, CD4-, CD8+, CD57+ TcR αβ samples were positive for both the CD8α and CD8β chains. These data were confirmed also by messenger RNA analysis. One additional case, with a peculiar phenotype (CD3-, CD2-, CD4-, CD8+, CD57-) and a germline configuration of the TcR β and γ chain genes, expressed only the CD8α chain. After additional phenotypic analysis with a wider panel of MoAbs, it was found that the β chain of the interleukin-2 receptor was constitutively expressed on the majority of the samples tested, and that most of the monoclonal samples coexpressed CD45RA/R0 antigens. Using MoAbs directed against the variable regions of the TcR β chain, we could show a preferential Vβ region restriction in the CD8+ monoclonal cases. This more extensive characterization of CD8+ LGL expansions has further documented the marked heterogeneity within this rare condition and allowed a better phenotypic dissection between the monoclonal and polyclonal cases.
|Number of pages||9|
|Publication status||Published - Oct 1 1992|
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