Diagnosis and monitoring in patients with hairy cell leukemia using the monoclonal antibody anti-HC2.

Overview

Immunofluorescent staining of peripheral blood mononuclear cells with the monoclonal antibody anti-HC2 combined with phase microscopic examination identified leukemic hairy cells in nine of 13 patients (69%) evaluated at Memorial Hospital prior to treatment with recombinant alpha-interferon (rIFN-alpha A). The remaining four patients required further studies of bone marrow or peripheral blood cytospin samples for diagnosis. In some cases a low percentage of cells staining with anti-HC2 could be significantly increased by depleting T cells from the sample using sheep red blood cell rosetting. These 13 patients represent a subgroup of patients treated on a phase II rIFN-alpha A study at Memorial Hospital. Ten patients (77%) achieved a partial response in a median of 128 days (range, 64-234). One patient achieved a minor response and two patients failed treatment. Nonhematologic toxicity, consisting of fever and malaise, was transient in all patients. Serial determinations of HC2-positive cells in the peripheral blood closely paralleled disease activity in the bone marrow in one patient treated for 4 years with various therapeutic modalities. The antibody anti-HC2 may play a significant role in the diagnosis and monitoring of hairy cell leukemia using peripheral blood sampling.