BACKGROUND: Atopy is defined as excess allergen-specific IgE (A-IgE). IgE is produced by plasma cells that differentiate from allergen-specific B cells. B cells are known to be killed by chemotherapy; however, it is not known whether A-IgE-secreting plasma cells are killed or inhibited by chemotherapy. If yes, serum A-IgE levels would be expected to decrease after chemotherapy. OBJECTIVES: We aimed to determine whether A-IgE levels in atopic individuals (serum A-IgE ≥0.35 kUA/L) decrease into the nonatopic range (< 0.35 kUA/L) after chemotherapy. METHODS: In 105 patients undergoing chemotherapy for acute leukemia, we measured serum A-IgE before and after chemotherapy. In a subset of these patients, we also measured B cell counts before and after chemotherapy. RESULTS: Of the 105 patients, 36 were atopic. In these patients, median A-IgE level before chemotherapy was 1.6 kUA/L whereas the median level after chemotherapy was 0.6 kUA/L (p < 0.001). In 12/36 (33%) patients, A-IgE levels decreased into the nonatopic range. In nonatopic patients (n = 69), the median A-IgE level also dropped: from 0.04 kUA/L before to 0.03 kUA/L after chemotherapy (p = 0.001). Among the total patients (n = 105), the median pre:post-chemotherapy A-IgE ratio was 1.8 (2.6 in atopic and 1.5 in nonatopic patients). In contrast, the median ratio of pre:post-chemotherapy B cell counts was 87.6. CONCLUSIONS: A-IgE levels decrease after chemotherapy but markedly less than B cell counts. Thus, at least some A-IgE plasma cells appear to survive chemotherapy.

Calgary Laboratory Services Calgary Alberta Canada

Department of Medicine University of Calgary Calgary Alberta Canada

Institute of Hematology and Blood Transfusion Prague Czech Republic

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