title: Phenotypic analysis of splenic lymphocytes and immunohistochemical study of hepatic granulomas after a murine infection with Salmonella abortusovis.
abstract: Infection in mice with an attenuated strain of Salmonella abortusovis (SAO), a specific pathogen for sheep, was used as a convenient model to understand further the induced immunity against SAO. The hypovirulent Rv6 strain, subcutaneously inoculated in salmonella-susceptible BALB/cby (Itys) mice, colonized the spleen and the liver in less than 6 days post-infection (PI) to be cleared after Day 28 PI. Simultaneously, an increase in spleen cell numbers, splenomegaly and hepatic granulomatous lesions developed to a maximum level on Day 9 PI. In spleen of uninfected mice, the number of Thy-1.2+ cells represents twice the number of surface immunoglobulin-positive cells (sIg+). Cytofluorometric analysis of the spleen lymphoid cell subsets showed a significant increase (10 times, P less than 0.05) in the number of sIg+ cells from Day 6 to Day 28 PI compared to control values. The number of Thy-1.2+ cells also significantly increased, to a lesser degree than the sIg+ cells, on Day 2 and on Day 16 PI (twice control values, P less than 0.05), but decreased on Day 6 PI compared to Day 2 PI. The highest L3T4+:Lyt-2+ ratio was observed on Day 2 PI and the lowest on Day 9 PI. On Day 28 PI, the number of sIg+ cells was still greater than the number of Thy-1.2+ cells. The granulomatous lesions were observed in the liver as early as Day 2 PI and their frequency was maximal on Day 9 PI. Immunohistochemical analysis of the granulomatous lesions showed that macrophages (F4/80+, Mac1+) were the basic cells and that L3T4+ cells were the predominant T cells. In well-developed granulomas observed on Day 9 PI, macrophages were in the centre whereas L3T4+ T cells were preferentially located at the periphery. T cells expressing Lyt-2 antigen were rarely detected. Variations in the proportion of lymphoid cells in the spleen and in hepatic granulomatous lesions suggest different and complementary effector mechanisms in induced immunity against SAO.
authors.affiliation: Unité de Pathologie Infectieuse et Immunologie, Institut National de la Recherche Agronomique (INRA), Nouzilly, France.
authors.forename: L
authors.initials: L
authors.lastname: Guilloteau
authors.forename: D
authors.initials: D
authors.lastname: Buzoni-Gatel
authors.forename: F
authors.initials: F
authors.lastname: Blaise
authors.forename: F
authors.initials: F
authors.lastname: Bernard
authors.forename: M
authors.initials: M
authors.lastname: Pépin
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000032:analysis; D005260:Female; D005455:Fluorescent Antibody Technique; D006099:Granuloma / Q000276:immunology*; D008099:Liver / Q000382:microbiology; D008107:Liver Diseases / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D012475:Salmonella / Q000254:growth & development; D012481:Salmonella Infections, Animal / Q000276:immunology* / Q000382:microbiology; D013154:Spleen / Q000276:immunology* / Q000382:microbiology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000954:Antigens, Surface