basophils constitute less than 1% of blood leukocytes and their pathophysiological roles in human allergic reactions remain mostly unclear , although basophil infiltration into the skin has been demonstrated in some human skin diseases [ 1 , 2 , 3 ] . recent studies have demonstrated that basophils play a critical role in the development of ige - mediated chronic allergic reactions by functioning as an initiator in mice [ 4 , 5 ] ; basophils also promote t helper ( th ) 2 skewing by antigen presentation in helminthic infections and in response to protease allergens in an ige - independent manner in mice [ 6 , 7 ] . additionally , a recent study has interestingly demonstrated that basophils play an essential role in antibody - mediated acquired immunity against ticks in mice . however , it remains unknown whether basophil infiltration might be involved in the infestation of ticks in humans . herein , we have evaluated the infiltration of basophils into human skin lesions of tick bites . during a 3-year period ( 20092011 ) , we have examined 8 patients with tick bites ( 3 males and 5 females , mean age  standard deviation [ sd ] 41.5  17.1 years , range 1862 ) . skin biopsies from skin lesions with tick bites were examined by hematoxylin - eosin staining and immunostaining . staining for basophils were incubated with anti - human basophil antibody ( 2d7 ) ( biolegend , san diego , calif . , usa ) , followed by incubation with biotinylated horse anti - mouse serum and then with avidin - biotin - peroxidase complex ( abc - ap ; vector laboratories , burlingame , calif . this study was carried out in accordance with the declaration of helsinki and was approved by the ethics committee of kyoto university , japan . informed consent was obtained from all patients enrolled in the study . eosin - positive binuclear cells and 2d7-immunoreactive cells represent eosinophils and basophils , respectively ( fig . basophils were observed to infiltrate into the skin lesions of 3 patients , but not in the other 5 patients . the numbers of infiltrating eosinophils and basophils were enumerated in 5 high - power fields ( table 1 ) . there was no significant correlation between the numbers of eosinophils and basophils infiltrating into the skin . in this report , we have evaluated the presence of basophils in human skin lesions of tick bites . intriguingly , we found that some cases did not exhibit basophil infiltration in spite of the infiltration of eosinophils . in addition , the number of basophils in the skin and the ratio of tissue basophils / eosinophils varies among skin diseases . the ratio of basophils / eosinophils is approximately 0.1 in atopic dermatitis , 1 in prurigo , long - lasting urticaria , bullous pemphigoid and eosinophilic pustular folliculitis , and greater than 1 in henoch - schnlein purpura . in our study , the average ratio  sd was 0.06  0.09 , which is quite a low value compared to other skin diseases . reported the low value of 0.1 in atopic dermatitis in their study could be due to biased cytokine milieu toward th1 in chronic skin lesions . it was also reported that the infiltration of basophils at tick - feeding sites of mice occurred during the second , but not the first tick infestation . considering these findings , the difference in our study may or may not be derived from the differences between the first infestation . although the number of patients in this study is limited , the absence or presence of basophils in tick bite lesions suggest that basophils might be involved in the development of acquired resistance to tick bites . further investigations might shed a light on the protection from tick bites .
recently , it has been described that basophils play an essential role in antibody - mediated acquired immunity against ticks in mice . 
 however , it is still unknown whether basophil infiltration has any significance in the infestation with ticks in humans . in this report 
 , we have evaluated the infiltration of basophils into human skin lesions of tick bites .