Analysis of Spleen Cells in Susceptible and Resistant Mice with Experimental Lagochilascariosis

Lagochilascariosis is an emerging parasitic disease caused by the helminth Lagochilascaris minor. The experimental mouse model has been used to study the immune response against L. minor infection. In the present work, immunohistochemistry analysis of spleen cells populations was evaluated in susceptible (C57BL/6) and resistant (BALB/c) mice experimentally infected with L. minor. The BALB/c mice exhibited increased spleen cell indexes as follows: F4/80+ at 100 days after infection (DPI), CD4+ at 100 and 250 DPI, CD8+ at 35 and 100 DPI, and CD19+ at 100, 150, and 250 DPI. In the spleens of the infected C57BL/6 mice, increased indexes of the following spleen cells were observed: F4/80+ cells at 250 DPI, CD4+ cells at 150 DPI, CD8+ cells at 35, 150, and 250 DPI, and CD19+ cells at 150 to 250 DPI. The index of spleen cells confirmed the differences between the control and infected groups at several time points following the infection. These data demonstrate an association between a preferential increase in the number of CD4+ and CD19+ spleen cells and resistance to experimental lagochilascariosis in BALB/c mice and between a preferential increase in the number of CD8+ spleen cells and susceptibility in C57BL/6 mice. 1. Introduction Lagochilascariosis is caused by Lagochilascaris minor, which can be the aetiological agent of the human infection; eventually,？？it is also found in domestic animals, such as dogs and cats [1]. Although it does not constitute a public health problem, lagochilascariosis is an emerging disease in Brazil; 90% of the described cases worldwide occur in this country [2]. Lagochilascariosis is a chronic disease characterised by the presence of granulomatous lesions in the oronasopharyngeal region that cause exudative abscesses with the presence of eggs, larvae, and adult parasites and indicate the occurrence of an autoinfection. This infection can be fatal if the parasite invades the lungs and the central nervous system [3, 4]. The natural life cycle and mechanism of infection of L. minor are still unclear because little is known about the biology of this parasite. Wild animals, such as dogs, felines, and rodents, are considered to be likely natural reservoirs of L. minor [2, 5]. The experimental heteroxenic life cycle of the parasite was described using mice as intermediate hosts and domestic cats as definitive hosts [6, 7]. The extraordinary capacity of L. minor to migrate to different human tissues has also been observed in experimental models [8]. In mice inoculated with infective parasite eggs containing third-stage larvae (L3),