Absolute and Relative Blood Lymphocyte Subset Counts before and during Treatment of Patients with Thrombotic Thrombocytopenic Purpura (TTP).

Background. Although the discovery of autoantibody-mediated ADAMTS-13 deficiency has contributed to the understanding of acquired TTP, the pathogenesis of TTP is not fully elucidated. We analyzed absolute and relative counts of T-, B- and natural killer (NK) cells during treatment and in relation to ADAMTS-13 activity.

Material and methods. Nine consecutive patients (pts; 3 male, 6 female; median age 53, range 22–76 years) with acquired TTP were included. All pts had daily therapeutic plasma exchange (TPE) with fresh frozen plasma (FFP). The median number of TPE was 14 (range 3–38). Observation time was 53 months (median; range 3–71). All pts achieved clinical remission, however 2 pts still have dialysis at follow-up (no 2 and 8). One pat relapsed (no 8), but responded to 22 TPE. ADAMTS-13 activity was analyzed before start of TPE and twice during the following month. Inhibitory antibodies to ADAMTS-13 was analyzed in pts with ADAMTS-13 activity <15%. Lymphocyte subsets (CD3, CD4, CD8, CD19/20, CD56) were analyzed on whole blood by flow cytometry using repeated analyses during the first month of treatment (median 4 analyses; range 3–5).

Results. See tables 1 and 2.

Conclusions. Five of nine (56%) pts had severe autoantibody-mediated ADAMTS-13 deficiency. These five pts had other autoantibodies in addition. Increased CD19/20 and decreased CD3 relative lymphocyte counts pretreatment were found in six pts, among them four with severe ADAMTS-13 deficiency. All but one normalized these counts during treatment. Further studies are needed in order to evaluate disturbancies in the relation of lymphocyte subsets in acquired TTP.