Despite increased CD4+Foxp3+ cells within the infection site, BALB/c IL-4 receptor-deficient mice reveal CD4+Foxp3-negative T cells as a source of IL-10 in Leishmania major susceptibility.
BALB/c IL-4Ralpha(-/-) mice, despite the absence of IL-4/IL-13 signaling and potent Th2 responses, remain highly susceptible to Leishmania major substain LV39 due exclusively to residual levels of IL-10. To address the contribution of CD4(+)CD25(+) T regulatory (Treg) cells to IL-10-mediated susceptibility, we depleted CD4(+)CD25(+) cells in vivo and reconstituted IL-4Ralpha x RAG2 recipients with purified CD4(+)CD25(-) T cells. Although anti-CD25 mAb treatment significantly decreased parasite numbers in IL-4Ralpha(-/-) mice, treatment with anti-IL-10R mAb virtually eliminated L. major parasites in both footpad and dermal infection sites. In addition, IL-4Ralpha x RAG2 mice reconstituted with CD4(+) cells depleted of CD25(+) Treg cells remained highly susceptible to infection. Analysis of L. major-infected BALB/c and IL-4Ralpha(-/-) inflammatory sites revealed that the majority of IL-10 was secreted by the CD4(+)Foxp3(-) population, with a fraction of IL-10 coming from CD4(+)Foxp3(+) Treg cells. All T cell IFN-gamma production was also derived from the CD4(+)Foxp3(-) population. Nevertheless, the IL-4Ralpha(-/-)-infected ear dermis, but not draining lymph nodes, consistently displayed 1.5- to 2-fold greater percentages of CD4(+)CD25(+) and CD4(+)Foxp3(+) Treg cells compared with the BALB/c-infected dermis. Thus, CD4(+)Foxp3(-) T cells are a major source of IL-10 that disrupts IFN-gamma activity in L. major-susceptible BALB/c mice. However, the increase in CD4(+)Foxp3(+) T cells within the IL-4Ralpha(-/-) dermis implies a possible IL-10-independent role for Treg cells within the infection site, and may indicate a novel immune escape mechanism used by L. major parasites in the absence of IL-4/IL-13 signaling.
Department of Microbiology, Immunology and Tropical Medicine, George Washington University Medical Center, Washington, DC 20037, USA.
Hisashi
H
Nagase
Kathryn M
KM
Jones
Charles F
CF
Anderson
Nancy
N
Noben-Trauth
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D020405:Dermis / Q000276:immunology / Q000469:parasitology / Q000473:pathology; D004423:Ear / Q000469:parasitology / Q000473:pathology; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000276:immunology*; D020022:Genetic Predisposition to Disease / Q000235:genetics; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000469:parasitology / Q000473:pathology; D007371:Interferon-gamma / Q000276:immunology; D016753:Interleukin-10 / Q000037:antagonists & inhibitors / Q000276:immunology*; D018793:Interleukin-13 / Q000276:immunology; D018320:Leishmania major / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D008198:Lymph Nodes / Q000276:immunology / Q000469:parasitology / Q000473:pathology; D008212:Lymphocyte Depletion; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D011956:Receptors, Cell Surface / Q000172:deficiency* / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000473:pathology; D018418:Th2 Cells / Q000276:immunology*; D053662:Interleukin-4 Receptor alpha Subunit
D000911:Antibodies, Monoclonal; D051858:Forkhead Transcription Factors; D007371:Interferon-gamma; D016753:Interleukin-10; D018793:Interleukin-13; D011956:Receptors, Cell Surface; C498833:Foxp3 protein, mouse; C504002:Il4ra protein, mouse; D053662:Interleukin-4 Receptor alpha Subunit