Azithromycin modulates immune response of human monocyte-derived dendritic cells and CD4 + T cells

ABSTRACT Immunity to Toxoplasma gondii at early stages of infection in C57BL/6 mice depends on gamma interferon (IFN-γ) production by NK cells, while at later stages it is primarily mediated by CD8 T cells. We decided to explore the requirement for CD4 T cells during T. gondii infection in Batf3−/− mice, which lack CD8α+ dendritic cells (DCs) that are necessary for cross-presentation of cell-associated antigens to CD8 T cells. We show that in this immunodeficient background on a BALB/c background, CD4 T cells become important effector cells and are able to protect Batf3−/− mice from infection with the avirulent strain RHΔku80Δrop5. Independently of the initial NK cell activation, CD4 T cells in wild-type and Batf3−/− mice were the major source of IFN-γ. Importantly, memory CD4 T cells were sufficient to provide protective immunity following transfer into Batf3−/− mice and secondary challenge with the virulent RHΔku80 strain. Collectively, these results show that under situations where CD8 cell responses are impaired, CD4 T cells provide an important alternative immune response to T. gondii. IMPORTANCE Toxoplasma gondii is a widespread parasite of animals that causes zoonotic infections in humans. Although healthy individuals generally control the infection with only moderate symptoms, it causes serious illness in newborns and those with compromised immune systems such as HIV-infected AIDS patients. Because rodents are natural hosts for T. gondii, laboratory mice provide an excellent model for studying immune responses. Here, we used a combination of an attenuated mutant strain of the parasite that effectively vaccinates mice, with a defect in a transcriptional factor that impairs a critical subset of dendritic cells, to studying the immune response to infection. The findings reveal that in BALB/c mice, CD4 memory T cells play a dominant role in producing IFN-γ needed to control chronic infection. Hence, BALB/c mice may provide a more appropriate model for declining immunity seen in HIV-AIDS patients where loss of CD4 cells is associated with emergence of opportunistic infections.

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CCL19 and CCL21 Chemokines Induce Endocytosis and Augment Antigen Presentation in Human Mature Dendritic Cells.

Blood ◽

10.1182/blood.v104.11.2651.2651 ◽

2004 ◽

Vol 104 (11) ◽

pp. 2651-2651

Author(s):

Masahiro Ogasawara ◽

Junji Tanaka ◽

Masahiro Imamura ◽

Masaharu Kasai

Keyword(s):

T Cells ◽

Dendritic Cells ◽

Antigen Presentation ◽

Cd4 T Cells ◽

Leukemia Cell ◽

Human Monocyte ◽

Blood Monocytes ◽

Gm Csf ◽

Cell Lysate ◽

Cytokines And Chemokines

Abstract Dendritic cells (DCs) are potent antigen presenting cells capable of regulating immune responses. DCs lose the ability to capture and process antigens during maturation. In the present study, we examined the effects of CCR7 ligands, CCL19 and CCL21, on endocytosis and antigen presentation in human mature dendritic cells. Immature DCs were generated from peripheral blood monocytes by culturing with GM-CSF and IL4 for 2–3 days. For maturation, immature DCs were cultured with the addition of TNFα, IL1β, IL6 and prostaglandin E2 for another 24 hours. Immature or mature DCs were incubated with FITC-dextran with or without CCL19. Immature DCs internalized FITC-dextran efficiently independent of the presence of CCL19 after 1 hour incubation. On the other hand, mature DCs scarcely internalized FITC-dextran without CCL19. In the presence of CCL19, however, mature DCs internalized FITC-dextran significantly (approximately 60% positive). The effect of CCL19 on the uptake of FITC-dextran in mature DCs was dose and time dependent. CCL21 exerted a similar effect on mature DCs. Next, we examined whether CCL19 facilitates antigen presentation in mature dendritic cells. CD4+ T cells were cultured with irradiated autologous mature DCs which had been incubated with leukemia cell lysate with or without CCL19. Marked proliferation of CD4+ T cells occurred only when these cells were cultured with mature DCs loaded with leukemia cell lysate in the presence of CCL19. This is the first demonstration that chemokines have a pivotal role in endocytosis and antigen presentation by human monocyte-derived dendritic cells to the best of our knowledge. These results demonstrated that generation of potent antigen-loaded mature DCs in relatively short term culture using various cytokines and chemokines may have an important clinical implication to facilitate DC-based immunotherapy.

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Suppression of the Immune Response to Human FVIII with FVIII Transgene Modified Tolerogenic Dendritic Cells in Hemophilic Mice

Blood ◽

10.1182/blood.v112.11.591.591 ◽

2008 ◽

Vol 112 (11) ◽

pp. 591-591

Author(s):

Rui-Jun Su ◽

Angela Epp ◽

Xiaoping Wu ◽

Neil Josephson

Keyword(s):

Immune Response ◽

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Regulatory T Cells ◽

Regulatory T Cell ◽

Cd4 T Cells ◽

Hemophilia A ◽

Tolerogenic Dendritic Cells

Abstract The development of anti-factor VIII (FVIII) inhibitory antibodies is currently the most significant complication of FVIII replacement therapy in the management of patients with hemophilia A. Infusion of in vitro generated tolerogenic dendritic cells (tDCs) loaded with foreign antigen has been shown to promote durable antigen-specific tolerance in vivo through mechanisms that involve the induction of regulatory T cells. In this study we evaluated the ability of tDCs transduced with a human B domain deleted FVIII transgene-expressing foamy virus (FV) vector to modulate the immune response to human FVIII in both naïve and pre-immunized hemophilia A mice. The tDCs were generated by flow sorting the population of CD11clowCD45RBhigh cells produced in culture of lineage negative bone marrow cells in RPMI1640/10%FBS supplemented with IL-10 and the neural peptides VIP and PACAP38. Expression of co-stimulatory molecules CD80 and CD86 and MHC Class II was negative or low on the generated tDCs and these cells remained un-activated even after stimulation with LPS or transduction by FV vectors. These tDCs produced low levels of IL-6 and TNF-α, and high level of IL-10. Furthermore, co-culture of the vector transduced tDCs with FVIII stimulated effector T cells (Teffs) resulted in decreased proliferation of Teffs and reduced secretion of IFN-γ and IL-2. In the cultures with the transduced tDCs there was also an increase in the number of apoptotic Teffs. Naïve Balb/c hemophilia A mice were treated with 2 weekly infusions of FVIII vector transduced tDCs (tDC-F8), control tDCs (tDCs-Ctrl), or no cells (Neg-Ctrl) prior to being challenged with four weekly intravenous doses of 0.2 μg rhFVIII. Following immunization the total cellularity and weights of spleens harvested from tDC-F8 mice were consistently half that of spleens from either tDC-Ctrl or Neg-Ctrl mice. Furthermore, inhibitor titers in tDC-F8 mice were 60–61% lower than either Neg-Ctrl or tDC-Ctrl mice (p < 0.05 compared to both controls). The regulatory T cell related markers FOXP3, CD25, CD103, CTLA4 and GITR were all up-regulated on splenic CD4+ T cells from tDC-F8 mice and the CD4+ T cell proliferation response to FVIII stimulation in splenocytes from tDC-F8 mice was suppressed by approximately 90%. Moreover, the rate of apoptosis in splenic T cells from tDC-F8 mice was 33% higher than splenic T cells from either Neg-Ctrl or tDC-Ctrl mice. In pre-immunized mice, treatment with 4 weekly infusions of FVIII vector transduced tDCs lowered inhibitor titers by 54% compared to no treatment controls (p < 0.05). In contrast, treatment with untransduced tDCs had no significant effect on the inhibitor titers of pre-immunized mice. Importantly, adoptive transfer of CD4+ T cells from tDC-8 mice produced suppression of the immune response to FVIII in subsequently immunized naïve secondary recipients.. In summary, these data indicate that FVIII vector transduced tDCs are useful in suppressing the immune response to FVIII in hemophilia A mice and suggest that regulatory T cells play a role in the induced immune modulation. More in vivo studies are in progress to confirm the durability of these effects. Future studies will also focus on isolating and characterizing the regulatory T cell populations induced by in vivo administration of transgene modified tDCs.

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