Selective ablation of basophils in mice reveals their nonredundant role in acquired immunity against ticks
Takeshi Wada, … , Naohiro Watanabe, Hajime Karasuyama
Takeshi Wada, … , Naohiro Watanabe, Hajime Karasuyama
Published July 26, 2010
Citation Information: J Clin Invest. 2010;120(8):2867-2875. https://doi.org/10.1172/JCI42680.
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Research Article

Selective ablation of basophils in mice reveals their nonredundant role in acquired immunity against ticks

Abstract

Ticks are ectoparasitic arthropods that can transmit a variety of microorganisms to humans and animals during blood feeding, causing serious infectious disorders, including Lyme disease. Acaricides are pharmacologic agents that kill ticks. The emergence of acaricide-resistant ticks calls for alternative control strategies for ticks and tick-borne diseases. Many animals develop resistance to ticks after repeated infestations, but the nature of this acquired anti-tick immunity remains poorly understood. Here we investigated the cellular and molecular mechanisms underlying acquired resistance to Haemaphysalis longicornis ticks in mice and found that antibodies were required, as was IgFc receptor expression on basophils but not on mast cells. The infiltration of basophils at tick-feeding sites occurred during the second, but not the first, tick infestation. To assess the requirement for basophil infiltration to acquired tick resistance, mice expressing the human diphtheria toxin receptor under the control of the mast cell protease 8 (Mcpt8) promoter were generated. Diphtheria toxin administration to these mice selectively ablated basophils. Diphtheria toxin–mediated basophil depletion before the second tick infestation resulted in loss of acquired tick resistance. These data provide the first clear evidence, to our knowledge, that basophils play an essential and nonredundant role in antibody-mediated acquired immunity against ticks, which may suggest new strategies for controlling tick-borne diseases.

Authors

Takeshi Wada, Kenji Ishiwata, Haruhiko Koseki, Tomoyuki Ishikura, Tsukasa Ugajin, Naotsugu Ohnuma, Kazushige Obata, Ryosuke Ishikawa, Soichiro Yoshikawa, Kaori Mukai, Yohei Kawano, Yoshiyuki Minegishi, Hiroo Yokozeki, Naohiro Watanabe, Hajime Karasuyama

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Figure 4

Generation of Mcpt8DTR mice for selective and inducible ablation of basophils.

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Generation of Mcpt8DTR mice for selective and inducible ablation of baso...
(A) Schematic diagram of Mcpt8DTR targeting construct. Exons are shown as black boxes. The restriction sites indicated are as follows: E, EcoRV; S, SalI; A, AflII. A SalI site engineered in the 3' untranslated region of the Mcpt8 gene was used to clone the IRES-DTR-EGFP-loxP-Neo-loxP cassettes. Neo cassette was removed by Cre-mediated recombination after mating with CAG-cre deleter mice. (B) Flow cytometric analysis of GFP expression in immune cells from Mcpt8DTR (white histogram) or wild-type littermate (shaded histogram) mice. Data are shown for basophils, neutrophils, and eosinophils in the bone marrow; mast cells in the peritoneal cavity; and T cells, B cells, NK cells, macrophages, plasmacytoid DCs (pDCs), and conventional DCs (cDCs) in the spleen. (C–F) Mcpt8DTR mice were treated with DT (750 ng/20 g body weight) or vehicle (PBS). The percentage of basophils (as indicated by the numbers in the panels) in the bone marrow and mast cells in the peritoneum 3 days after the injection are shown in C. The change in percentage of basophils in the peripheral blood after the injection is plotted in D. The number of mast cells in the flank skin 3 days after the injection is shown in E. Data are shown as mean ± SEM, n = 3 each. (F) Mice were subjected to passive cutaneous anaphylaxis 3 days after the DT injection. Data are shown as mean ± SEM, n = 4 each. Data shown in B–F are representative of at least 3 repeated experiments. *P < 0.05.