Alteration in mononuclear cell subpopulations in dogs immunized with gentamicin-attenuated Leishmania infantum

The impact of immunization with gentamicin-attenuated Leishmania infantum (H-line) on the immunophenotypic profile of popliteal lymph node (PLN) and peripheral blood mononuclear cells (PBMCs) of dogs was assessed by flow cytometry and immunohistochemistry. Compared with the dogs infected with L. infantum wild-type (Group WT), there was a significantly higher percentage of CD4+, CD44+ T cells and CD14+, MHC-II+ cells and a lower percentage of CD4+ CD25+ regulatory T cells in PLN of the immunized dogs with L. infantum H-line (Group H). The percentage of CD4+ and CD8+ T cells in PBMCs of immunized dogs was higher than that in dogs of Group WT. The CD4:CD8 ratio in PLN of dogs of Group H was significantly higher than that in dogs of Group WT. A significantly higher percentage of CD21+ B cells and a lower percentage of CD79b+ cells were found in PLN of the immunized dogs compared with dogs of Group WT. Immunohistochemical investigation showed no parasites in the PLN of immunized dogs whereas there were parasites in the PLN of 60% of dogs infected with L. infantum WT. In this study, the immunophenotypic profile of mononuclear cells of the immunized dogs correlates with cellular immunity.