Studies on the development and role of some cell-mediated immune responses in experimental toxocarosis in mice |
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Authors: | Natalia Wnukowska Tadeusz H Dzbeński |
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Institution: | (1) Department of Medical Parasitology, National Institute of Hygiene, Chocimska 24, 00-791 Warsaw, Poland |
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Abstract: | The studies were undertaken to investigate the development of some cell-mediated immune responses in experimental toxocarosis
in mice and to assess the influence of these responses on the course of infection. Mice were infected orally with 350 eggs
of Toxocara canis and reinfected with the same dose of parasites after 8 weeks. Groups of infected animals were killed each week of the experiments
to obtain spleens, livers and brains for further studies. Lymphocytes from removed spleens were analysed by flow-cytometry
for CD4 and CD8 expression and cultured in vitro to measure their responses to Concanavalin A and excretory-secretory (ES) antigen of T. canis in a lymphocyte transformation test. Pieces of livers were used to prepare paraffin sections to be stained later with haematoxylin
and eosin, whereas whole brains of the infected animals were examined for the presence of parasite larvae. The results of
the studies showed depression of T-cell responses to ConA in early stages of infection and significant increase in the blastogenic
responses to the ES antigen from week 4 following infection. The depression of T-cell responses was accompanied by lowered
CD4+/CD8+ ratio resulting from increased percentages of CD8+ T cells. Histopathological examination of liver sections revealed
trapping of larvae in T. canis reinfected mice. The intensity of infection as measured by larval recoveries from the brains of mice increased gradually
up to the 8th week of infection, but did not show significant changes after reinfection, testifying to the development of
long-lasting protective immunity during primary infection. |
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Keywords: | Toxocara canis CMI responses protective immunity |
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