Cellular immune reconstitution after subcutaneous alemtuzumab (anti-CD52 monoclonal antibody, CAMPATH-1H) treatment as first-line therapy for B-cell chronic lymphocytic leukaemia

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Abstract
Little information is available on long-term immune reconstitution after therapy with alemtuzumab in B-CLL patients. We present long-term follow-up data for blood lymphocyte subsets analysed by flow cytometry in previously untreated B-CLL patients who received alemtuzumab subcutaneously as first-line therapy. All lymphoid subsets were significantly (P+, CD8+, CD3-56+ (natural killer (NK)), CD3+56+ (NK–T) and CD19+5- (normal B) cells were 43, 20, 4, 1 and 8 cells/l, respectively. The median cell count of all subsets remained at 9 months post-treatment. CD4+ and CD8+ levels in blood had reached >100 cells/l in >50% of the patients at 4 months after the end of treatment. One patient had a cytomegalovirus reactivation and one patient developed Pneumocystis carinii pneumonia during therapy. No opportunistic or other major infections were recorded during unmaintained, long-term follow-up. There was no correlation between the cumulative dose of alemtuzumab and the severity or length of immunosuppression. CD52- T-cell subsets occurred during the treatment and comprised >80% of all CD4+ and CD8+ cells in the blood at the end of therapy. These subpopulations declined gradually during unmaintained follow-up. The relationship between these observations and the safety/antitumour effects of alemtuzumab is discussed.