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Low dose Leishmania major promotes a transient T helper cell type 2 response that is down-regulated by interferon gamma-producing CD8+ T cells.

Uzonna JE, Joyce KL, Scott P - J. Exp. Med. (2004)

Bottom Line: An unresolved issue in the field of T helper (Th) cell development relates to the findings that low doses of antigen promote Th2 cell development in vitro, whereas several classic in vivo studies suggest the opposite.In the absence of CD8+ T cells, the Th2 response was maintained.Thus, the discrepant results seen between in vivo and in vitro studies on the effects of antigen dose on Th cell differentiation may depend upon whether CD8+ T cells participate in the immune response.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia 19104, USA.

ABSTRACT
An unresolved issue in the field of T helper (Th) cell development relates to the findings that low doses of antigen promote Th2 cell development in vitro, whereas several classic in vivo studies suggest the opposite. Here we resolve this paradox by studying the early immune response in mice after infection with different doses of Leishmania major. We found that low parasite doses induced a Th2 response in C57BL/6 (B6) mice, whereas high doses induced a Th1 response. However, the Th2 response in low dose-infected mice was transient and the animals healed. The appearance of a Th1 response after low dose infection was dependent upon the concomitant activation of interferon gamma-producing CD8+ T cells. In the absence of CD8+ T cells, the Th2 response was maintained. However, either neutralization of interleukin (IL)-4 or administration of IL-12 promoted a Th1 response after low dose infection of CD8-deficient mice, indicating that the required role for CD8+ T cells was limited to modulation of CD4+ T cell responses. Thus, the discrepant results seen between in vivo and in vitro studies on the effects of antigen dose on Th cell differentiation may depend upon whether CD8+ T cells participate in the immune response.

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CD8+ T cells are required for downmodulation of low dose–induced Th2 responses and susceptibility to L. major. (A and B) L. major infection induces proliferation and IFN-γ production by CD8+ T cells in B6 (WT) mice. The dLN cells from B6 mice infected with low and high dose L. major for 3 wk were labeled with CFSE, stimulated with SLA for 5 d, and stained for intracellular IFN-γ. (A) Proliferation (gated on live CD8+ cells) and (B) IFN-γ production by CD8+ T cells was analyzed by flow cytometry. (C and D) CD8+ T cells are required for resistance to low dose, but are dispensable for high dose L. major infection. Course of lesion progression (C) and parasite burden (D) in the ear of WT, CD8, and β2m-deficient mice infected with low and high dose L. major. (E) In the absence of CD8+ T cells, the low dose–induced Th2 response is sustained. CD8-deficient mice infected with low and high doses of L. major were killed at 13 wk, the dLN cells were stimulated with SLA for 3 d, and the production of IFN-γ and IL-4 was measured by ELISA. Representative data from three experiments with similar results are presented.
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fig2: CD8+ T cells are required for downmodulation of low dose–induced Th2 responses and susceptibility to L. major. (A and B) L. major infection induces proliferation and IFN-γ production by CD8+ T cells in B6 (WT) mice. The dLN cells from B6 mice infected with low and high dose L. major for 3 wk were labeled with CFSE, stimulated with SLA for 5 d, and stained for intracellular IFN-γ. (A) Proliferation (gated on live CD8+ cells) and (B) IFN-γ production by CD8+ T cells was analyzed by flow cytometry. (C and D) CD8+ T cells are required for resistance to low dose, but are dispensable for high dose L. major infection. Course of lesion progression (C) and parasite burden (D) in the ear of WT, CD8, and β2m-deficient mice infected with low and high dose L. major. (E) In the absence of CD8+ T cells, the low dose–induced Th2 response is sustained. CD8-deficient mice infected with low and high doses of L. major were killed at 13 wk, the dLN cells were stimulated with SLA for 3 d, and the production of IFN-γ and IL-4 was measured by ELISA. Representative data from three experiments with similar results are presented.

Mentions: Because the Th2 response induced by low dose infection was transient, we explored the possibility that non-CD4+ T cells responding to Leishmania antigen may regulate Th cell responses. We found that both high and low dose L. major infections were associated with a robust CD8+ T cell proliferative response (Fig. 2 A), and a significant percentage of these CD8+ T cells produced IFN-γ (Fig. 2 B). Therefore, we hypothesized that CD8+ T cells might contribute to reversing the early Th2 response seen in low dose L. major infection. Consistent with this idea was a recent finding that CD8+ T cells are required for healing a low dose infection with L. major (13). However, this contrasts with several previous studies demonstrating that CD8+ T cells are not required for control of a primary infection (19–21). To determine if the discrepancy in these results was related to infection dose, and whether IFN-γ–producing CD8+ T cells were involved in modulating the initial Th2 response, we infected CD8+ T cell–deficient mice, both CD8 and β2m KO animals, with low or high doses of L. major. Similar to infected WT mice, at 3 wk after infection cells from low dose–infected CD8 T cell–deficient mice produced more IL-4 and less IFN-γ, whereas those from high dose–infected mice produced no IL-4, but high levels of IFN-γ (unpublished data). Neither CD8 nor β2m-deficient mice were able to resolve disease after low dose infections, whereas high dose infection was associated with disease resolution in both strains of mice (Fig. 2, C and D). Consistent with a role for CD8+ T cells in down-regulation of Th2 responses, at 13 wk IL-4 production by cells from low dose–infected CD8-deficient mice was significantly greater than that produced by cells from WT mice (Fig. 2 E). Correspondingly, the IFN-γ response in low dose–infected CD8-deficient animals remained low relative to either low dose–infected WT mice or either mouse strain infected with a high dose of parasites (Fig. 2 E). These results strongly implicate CD8+ T cells as important for down-regulating the early Th2 response in low dose–infected mice.


Low dose Leishmania major promotes a transient T helper cell type 2 response that is down-regulated by interferon gamma-producing CD8+ T cells.

Uzonna JE, Joyce KL, Scott P - J. Exp. Med. (2004)

CD8+ T cells are required for downmodulation of low dose–induced Th2 responses and susceptibility to L. major. (A and B) L. major infection induces proliferation and IFN-γ production by CD8+ T cells in B6 (WT) mice. The dLN cells from B6 mice infected with low and high dose L. major for 3 wk were labeled with CFSE, stimulated with SLA for 5 d, and stained for intracellular IFN-γ. (A) Proliferation (gated on live CD8+ cells) and (B) IFN-γ production by CD8+ T cells was analyzed by flow cytometry. (C and D) CD8+ T cells are required for resistance to low dose, but are dispensable for high dose L. major infection. Course of lesion progression (C) and parasite burden (D) in the ear of WT, CD8, and β2m-deficient mice infected with low and high dose L. major. (E) In the absence of CD8+ T cells, the low dose–induced Th2 response is sustained. CD8-deficient mice infected with low and high doses of L. major were killed at 13 wk, the dLN cells were stimulated with SLA for 3 d, and the production of IFN-γ and IL-4 was measured by ELISA. Representative data from three experiments with similar results are presented.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2211781&req=5

fig2: CD8+ T cells are required for downmodulation of low dose–induced Th2 responses and susceptibility to L. major. (A and B) L. major infection induces proliferation and IFN-γ production by CD8+ T cells in B6 (WT) mice. The dLN cells from B6 mice infected with low and high dose L. major for 3 wk were labeled with CFSE, stimulated with SLA for 5 d, and stained for intracellular IFN-γ. (A) Proliferation (gated on live CD8+ cells) and (B) IFN-γ production by CD8+ T cells was analyzed by flow cytometry. (C and D) CD8+ T cells are required for resistance to low dose, but are dispensable for high dose L. major infection. Course of lesion progression (C) and parasite burden (D) in the ear of WT, CD8, and β2m-deficient mice infected with low and high dose L. major. (E) In the absence of CD8+ T cells, the low dose–induced Th2 response is sustained. CD8-deficient mice infected with low and high doses of L. major were killed at 13 wk, the dLN cells were stimulated with SLA for 3 d, and the production of IFN-γ and IL-4 was measured by ELISA. Representative data from three experiments with similar results are presented.
Mentions: Because the Th2 response induced by low dose infection was transient, we explored the possibility that non-CD4+ T cells responding to Leishmania antigen may regulate Th cell responses. We found that both high and low dose L. major infections were associated with a robust CD8+ T cell proliferative response (Fig. 2 A), and a significant percentage of these CD8+ T cells produced IFN-γ (Fig. 2 B). Therefore, we hypothesized that CD8+ T cells might contribute to reversing the early Th2 response seen in low dose L. major infection. Consistent with this idea was a recent finding that CD8+ T cells are required for healing a low dose infection with L. major (13). However, this contrasts with several previous studies demonstrating that CD8+ T cells are not required for control of a primary infection (19–21). To determine if the discrepancy in these results was related to infection dose, and whether IFN-γ–producing CD8+ T cells were involved in modulating the initial Th2 response, we infected CD8+ T cell–deficient mice, both CD8 and β2m KO animals, with low or high doses of L. major. Similar to infected WT mice, at 3 wk after infection cells from low dose–infected CD8 T cell–deficient mice produced more IL-4 and less IFN-γ, whereas those from high dose–infected mice produced no IL-4, but high levels of IFN-γ (unpublished data). Neither CD8 nor β2m-deficient mice were able to resolve disease after low dose infections, whereas high dose infection was associated with disease resolution in both strains of mice (Fig. 2, C and D). Consistent with a role for CD8+ T cells in down-regulation of Th2 responses, at 13 wk IL-4 production by cells from low dose–infected CD8-deficient mice was significantly greater than that produced by cells from WT mice (Fig. 2 E). Correspondingly, the IFN-γ response in low dose–infected CD8-deficient animals remained low relative to either low dose–infected WT mice or either mouse strain infected with a high dose of parasites (Fig. 2 E). These results strongly implicate CD8+ T cells as important for down-regulating the early Th2 response in low dose–infected mice.

Bottom Line: An unresolved issue in the field of T helper (Th) cell development relates to the findings that low doses of antigen promote Th2 cell development in vitro, whereas several classic in vivo studies suggest the opposite.In the absence of CD8+ T cells, the Th2 response was maintained.Thus, the discrepant results seen between in vivo and in vitro studies on the effects of antigen dose on Th cell differentiation may depend upon whether CD8+ T cells participate in the immune response.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia 19104, USA.

ABSTRACT
An unresolved issue in the field of T helper (Th) cell development relates to the findings that low doses of antigen promote Th2 cell development in vitro, whereas several classic in vivo studies suggest the opposite. Here we resolve this paradox by studying the early immune response in mice after infection with different doses of Leishmania major. We found that low parasite doses induced a Th2 response in C57BL/6 (B6) mice, whereas high doses induced a Th1 response. However, the Th2 response in low dose-infected mice was transient and the animals healed. The appearance of a Th1 response after low dose infection was dependent upon the concomitant activation of interferon gamma-producing CD8+ T cells. In the absence of CD8+ T cells, the Th2 response was maintained. However, either neutralization of interleukin (IL)-4 or administration of IL-12 promoted a Th1 response after low dose infection of CD8-deficient mice, indicating that the required role for CD8+ T cells was limited to modulation of CD4+ T cell responses. Thus, the discrepant results seen between in vivo and in vitro studies on the effects of antigen dose on Th cell differentiation may depend upon whether CD8+ T cells participate in the immune response.

Show MeSH
Related in: MedlinePlus