Background and objectives: Imatinib mesylate inhibits ABL tyrosine kinase. This protein serves a complex role in cell cycling and is important in lymphopoiesis. We describe the immunologic findings in patients with chronic myeloid leukemia resistant to or intolerant of interferon (IFN) a who were treated with imatinib. This aspect could be of interest since patients with these characteristics may be exposed to this treatment for long periods.
Design and methods: Immunologic and hematologic evaluation (including immunoglobulin levels and parameters of autoimmunity), immunophenotyping analysis of peripheral blood and bone marrow, and cytogenetic bone marrow analysis were performed at sequential time points of the treatment (0, 3, 6, and 9 and 12 months). The relationships among immunologic variables, and between the immunologic findings and response, were investigated.
Results: Hypogammaglobulinemia IgG, IgA and IgM developed in 28%, 14% and 22% of the patients, respectively. Lymphocyte counts decreased significantly along the treatment. No correlation was found between Ig levels and lymphocyte counts or CD4, CD8 or CD19 subpopulations in peripheral blood, nor between Ig levels and bone marrow B-lineage precursors. No autoimmune phenomena were detected. Hypogammaglobulinemia had no clinical repercussions in patients who developed it. The percentage reductions of IgG, IgA and IgM levels were higher in patients with major genetic response to imatinib.
Interpretation and conclusions: Hypogammaglobulinemia can develop in as many as 20-25% of patients with chronic myeloid leukemia previously exposed to IFN a and who are then treated with imatinib. The reduction of Ig is greater in patients with a better cytogenetic response, perhaps reflecting that the efficacy of imatinib in blocking BCR-ABL kinase activity runs in parallel with ABL inhibition, leading to a dysregulation of B-lymphocyte function. Close immunologic evaluation is recommended in these patients.