LARGE GRANULAR LYMPHOCYTE EXPANSIONS IN FELTYS-SYNDROME HAVE AN UNUSUAL PHENOTYPE OF ACTIVATED CD45RA+ CELLS

One-third of patients with Felty's syndrome (FS) have significant clon al expansions of CD3+ CD8+ large granular lymphocytes (LGLs) in their peripheral blood. The reasons for this are unclear, but one hypothesis is that they are activated antigen-specific cells of pathogenic relev ance. Cytofluorographic analysis of activation markers demonstrated th at the cell surface phenotype of these expansions was CD57+, HLA-DR+, IL-2R-, Leu-8+, CD69+, LFA-1+, ICAM-1+, VLA-4+, i.e. 'activated' T cel ls. However, they also expressed the phenotype CD45RA+, CD45RB(bright) , CD45RO-, usually associated with 'naive' cells. This could result fr om aberrant activation, malignant transformation or from a 'reversal' of CD45 phenotype following chronic antigenic stimulation. In three pa tients with RA and non-clonal LGL expansions, a more variable phenotyp e was found. In one of these patients, the expanded population was ide ntified in the peripheral blood, but not the synovial fluid. This may suggest that at least in this individual, any pathogenic effect is exe rted systemically.