Leishmania mexicana promastigotes induce cytotoxic T lymphocytes in vivo that do not recognize infected macrophages

The question is addressed whether antigens of Leishmania, a parasite residing in the endosomal compartment of macrophages, can be presented in the context of major histocompatibility complex class I molecules. We used E. coli β-galactosidase as a model antigen which can be expressed in high levels in L. mexicana promastigotes (L. mexicana-gal). Infection of BALB/c mice with L. mexicanagal induces β-galactosidase-specific cytotoxic T cells (CTL), which can be isolated using a β-galactosidase-expressing mastocytoma line as an antigen-presenting cell. These CTL recognize epitopes of β-galactosidase in the context of H-2K^d; however, they do not recognize L. mexicanagal-infected macrophages even after killing of the intracellular amastigotes by drug treatment or macrophage activation by lymphokines, although class I-peptide interaction and the presentation of endogenously produced antigens is normal. It is concluded that parasite antigens can induce a CTL response in vivo but that these CTL cannot recognize infected macrophages because the relevant epitopes cannot gain access to class I molecules. The effect of priming in vivo may be explained by the well-known but ill-understood phenomenon of cross-priming.     

Correlations of the expression of γδ T cells and their co‐stimulatory molecules TIGIT,PD‐1, ICOS and BTLA with PR and PIBF in the peripheral blood and decidual tissues of women with unexplained recurrent spontaneous abortion

Semi‐allogeneic embryos are not rejected by the maternal immune system due to maternal–fetal immune tolerance. Progesterone (P) receptor (PR)‐expressing γδ T cells are present in healthy pregnant women. In the presence of P, these cells secrete an immunomodulatory protein called progesterone‐induced blocking factor (PIBF), which can facilitate immune escape and is important in preventing embryonic rejection. This work investigated the correlations of the expression of γδ T cells and their co‐stimulatory molecules T cell immunoglobulin and ITIM domain (TIGIT), programmed cell death 1 (PD‐1), inducible co‐stimulator (ICOS) and B and T lymphocyte attenuator (BTLA) with progesterone receptor (PR) and progesterone‐induced blocking factor (PIBF) in peripheral blood and decidual tissue in women with unexplained recurrent spontaneous abortion (URSA) and normal pregnant (NP) women. We confirmed that γδ T cell proportions and PIBF expression in the peripheral blood and decidua of URSA women decreased significantly, while PR expression in decidua decreased. However, TIGIT, PD‐1, ICOS and BTLA expression in γδ T cells in peripheral blood did not change, while TIGIT and PD‐1 expression in γδ T cells in decidua increased significantly. Under the action of PHA‐P (10 µg/ml), co‐blocking of TIGIT (15 µg/ml) and PD‐1 (10 µg/ml) antibodies further induced γδ T cell proliferation, but PIBF levels in the culture medium supernatant did not change. At 10^?10 M P, γδ T cells proliferated significantly, and PIBF concentrations in the culture medium supernatant increased. γδ T cells co‐cultured with P, TIGIT and PD‐1 blocking antibodies showed the most significant proliferation, and PIBF concentrations in the culture medium supernatant were the highest. These results confirm that P is necessary for PIBF production. The TIGIT and PD‐1 pathways participate in γδ T cell proliferation and activation and PIBF expression and play important roles in maintaining pregnancy.     

Type I interferon potentiates T‐cell receptor mediated induction of IL‐10‐producing CD4+ T cells

Type I interferons (IFNs) have the dual ability to promote the development of the immune response and exert an anti‐inflammatory activity. We analyzed the integrated effect of IFN‐α, TCR signal strength, and CD28 costimulation on human CD4⁺ T‐cell differentiation into cell subsets producing the anti‐ and proinflammatory cytokines IL‐10 and IFN‐γ. We show that IFN‐α boosted TCR‐induced IL‐10 expression in activated peripheral CD45RA⁺CD4⁺ T cells and in whole blood cultures. The functional cooperation between TCR and IFN‐α efficiently occurred at low engagement of receptors. Moreover, IFN‐α rapidly cooperated with anti‐CD3 stimulation alone. IFN‐α, but not IL‐10, drove the early development of type I regulatory T cells that were mostly IL‐10⁺ Foxp3^? IFN‐γ^? and favored IL‐10 expression in a fraction of Foxp3⁺ T cells. Our data support a model in which IFN‐α costimulates TCR toward the production of IL‐10 whose level can be amplified via an autocrine feedback loop.     

Characteristics of Schistosoma japonicum infection induced IFN‐γ and IL‐4 co‐expressing plasticity Th cells

Schistosoma japonicum infection can induce granulomatous inflammation and cause tissue damage in the mouse liver. The cytokine secretion profile of T helper (Th) cells depends on both the nature of the activating stimulus and the local microenvironment (e.g. cytokines and other soluble factors). In the present study, we found an accumulation of large numbers of IFN‐γ⁺ IL‐4⁺ CD4⁺ T cells in mouse livers. This IFN‐γ⁺ IL‐4⁺ cell population increased from 0·68 ± 0·57% in uninfected mice to 7·05 ± 3·0% by week 4 following infection and to 9·6 ± 5·28% by week 6, before decreasing to 6·3 ± 5·9% by week 8 in CD4 T cells. Moreover, IFN‐γ⁺ IL‐4⁺ Th cells were also found in mouse spleen and mesenteric lymph nodes 6 weeks after infection. The majority of the IFN‐γ⁺ IL‐4⁺ Th cells were thought to be related to a state of immune activation, and some were memory T cells. Moreover, we found that these S. japonicum infection‐induced IFN‐γ⁺ IL‐4⁺ cells could express interleukin‐2 (IL‐2), IL‐9, IL‐17 and high IL‐10 levels at 6 weeks after S. japonicum infection. Taken together, our data suggest the existence of a population of IFN‐γ⁺ IL‐4⁺ plasticity effector/memory Th cells following S. japonicum infection in C57BL/6 mice.     

Carbon monoxide‐treated dendritic cells decrease β1‐integrin induction on CD8+ T cells and protect from type 1 diabetes

Carbon monoxide (CO) treatment improves pathogenic outcome of autoimmune diseases by promoting tolerance. However, the mechanism behind this protective tolerance is not yet defined. Here, we show in a transgenic mouse model for autoimmune diabetes that ex vivo gaseous CO (gCO)‐treated DCs loaded with pancreatic β‐cell peptides protect mice from disease. This protection is peptide‐restricted, independent of IL‐10 secretion by DCs and of CD4⁺ T cells. Although no differences were observed in autoreactive CD8⁺ T‐cell function from gCO‐treated versus untreated DC‐immunized groups, gCO‐treated DCs strongly inhibited accumulation of autoreactive CD8⁺ T cells in the pancreas. Interestingly, induction of β1‐integrin was curtailed when CD8⁺ T cells were primed with gCO‐treated DCs, and the capacity of these CD8⁺ T cells to lyse isolated islet was dramatically impaired. Thus, immunotherapy using CO‐treated DCs appears to be an original strategy to control autoimmune disease.     

IL‐10 interferes directly with TCR‐induced IFN‐γ but not IL‐17 production in memory T cells

IL‐10 is a potent immunoregulatory and anti‐inflammatory cytokine. However, therapeutic trials in chronic inflammation have been largely disappointing. It is well established that IL‐10 can inhibit Th1 and Th2 cytokine production via indirect effects on APC. Less data are available about the influence of IL‐10 on IL‐17 production, a cytokine which has been recently linked to chronic inflammation. Furthermore, there are only few reports about a direct effect of IL‐10 on T cells. We demonstrate here that IL‐10 can directly interfere with TCR‐induced IFN‐γ production in freshly isolated memory T cells in the absence of APC. This effect was independent of the previously described effects of IL‐10 on T cells, namely inhibition of IL‐2 production and inhibition of CD28 signaling. In contrast, IL‐10 did not affect anti‐CD3/anti‐CD28‐induced IL‐17 production from memory T cells even in the presence of APC. This might have implications for the interpretation of therapeutic trials in patients with chronic inflammation where Th17 cells contribute to pathogenesis.     

TGF‐β downregulates KLRG1 expression in mouse and human CD8+ T cells

The inhibitory receptor killer cell lectin‐like receptor G1 (KLRG1) and the integrin α_E (CD103) are expressed by CD8⁺ T cells and both are specific for E‐cadherin. However, KLRG1 ligation by E‐cadherin inhibits effector T‐cell function, whereas binding of CD103 to E‐cadherin enhances cell–cell interaction and promotes target cell lysis. Here, we demonstrate that KLRG1 and CD103 expression in CD8⁺ T cells from untreated and virus‐infected mice are mutually exclusive. Inverse correlation of KLRG1 and CD103 expression was also found in human CD8⁺ T cells‐infiltrating hepatocellular carcinomas. As TGF‐β is known to induce CD103 expression in CD8⁺ T cells, we examined whether this cytokine also regulates KLRG1 expression. Indeed, our data further reveal that TGF‐β signaling in mouse as well as in human CD8⁺ T cells downregulates KLRG1 expression. This finding provides a rationale for the reciprocal expression of KLRG1 and CD103 in different CD8⁺ T‐cell subsets. In addition, it points to the limitation of KLRG1 as a marker for terminally differentiated CD8⁺ T cells if lymphocytes from tissues expressing high levels of TGF‐β are analyzed.     

Sympathetic neural signaling via the β2‐adrenergic receptor suppresses T‐cell receptor‐mediated human and mouse CD8+ T‐cell effector function

Postganglionic sympathetic neurons innervate secondary lymphoid organs and secrete norepinephrine (NE) as the primary neurotransmitter. NE binds and signals through five distinct members of the adrenergic receptor family. In this study, we show elevated expression of the β2‐adrenergic receptor (ADRB2) on primary human CD8⁺ effector memory T cells. Treatment of both human and murine CD8⁺ T cells with NE decreased IFN‐γ and TNF‐α secretion and suppressed their cytolytic capacity in response to T‐cell receptor (TCR) activation. The effects of NE were specifically reversed by β 2‐specific antagonists. Adrb2^?/? CD8⁺ T cells were completely resistant to the effects of NE. Further, the ADRB2‐specific pharmacological ligand, albuterol, significantly suppressed effector functions in both human and mouse CD8⁺ T cells. While both TCR activation and stimulation with IL‐12 + IL‐18 were able to induce inflammatory cytokine secretion, NE failed to suppress IFN‐γ secretion in response to IL‐12 + IL18. Finally, the long‐acting ADRB2‐specific agonist, salmeterol, markedly reduced the cytokine secretion capacity of CD8⁺ T cells in response to infection with vesicular stomatitis virus. This study reveals a novel intrinsic role for ADRB2 signaling in CD8⁺ T‐cell function and underscores the novel role this pathway plays in adaptive T‐cell responses to infection.     

IL‐15 modulates the balance between Bcl‐2 and Bim via a Jak3/1‐PI3K‐Akt‐ERK pathway to promote CD8αα+ intestinal intraepithelial lymphocyte survival

IL‐15 is an essential survival factor for CD8αα⁺ intestinal intraepithelial lymphocytes (iIELs) in vitro and in vivo. However, the IL‐15‐induced survival signals in primary CD8αα⁺ iIELs remains elusive. Although Bcl‐2 level in CD8αα⁺ iIELs positively correlates with IL‐15Rα expression in the intestinal epithelial cells, overexpression of Bcl‐2 only moderately restores CD8αα⁺ γδ iIELs in Il15^?/? mice. Here, we found that IL‐15 promptly activated a Jak3‐Jak1‐PI3K‐Akt pathway that led to the upregulation of Bcl‐2 and Mcl‐1. This pathway also induced a delayed but sustained ERK1/2 activation, which not only was necessary for the maintenance of Bcl‐2 but also resulted in the phosphorylation of extra‐long Bim at Ser⁶⁵. The latter event facilitated the dissociation of Bim from Bcl‐2 without affecting Bim abundance in IL‐15‐treated CD8αα⁺ iIELs. Using an adoptive cell transfer approach, we found that either overexpression of Bcl‐2 or removal of Bim from CD8αα⁺ iIELs promoted their survival in Il15ra^?/? mice. Taken together, IL‐15 promotes CD8αα⁺ iIEL survival by both increasing Bcl‐2 levels and dissociating Bim from Bcl‐2 through activation of a Jak3‐Jak1‐PI3K‐Akt‐ERK1/2 pathway, which differs from a previously reported IL‐15‐induced survival signal.     

T‐cell homeostasis in chronic HCV‐infected patients treated with interferon and ribavirin or an interferon‐free regimen

Direct‐acting antiviral has replaced pegylated interferon‐α and ribavirin‐based treatment in the treatment of chronic hepatitis C virus (HCV) infection. While interferon‐α is immune modulating and causes lymphopenia, interferon‐free regimens seem to be well‐tolerated. This study aimed to compare T‐cell homeostasis before, during, and after HCV treatment with or without interferon‐α in patients with chronic HCV infection. A total of 20 patients with chronic HCV infection were treated with pegylated interferon‐α and ribavirin, and six patients were treated with an interferon‐free regimen. All patients were treated for a minimum of 12 weeks. Interferon‐α treatment caused an increase in the density of the receptor for IL‐7 (IL‐7Rα) during treatment, while interferon‐free regimens caused a decrease in IL‐7Rα density. After a sustained viral response, proportions of IL‐7Rα+ T cells and IL‐7Rα density decreased compared to prior treatment values. Finally, a proportion of CD8+ effector memory was lower while proportion of apoptotic T cells was higher after sustained virologic response compared to prior treatment. Despite lymphopenia during interferon, alterations in T‐cell homeostasis during treatment were relatively similar in patients receiving interferon‐based treatment and in patients receiving interferon‐free treatment, and alterations during and after treatment seem to illustrate a reduced need for high levels of T cells aimed at controlling infection.     

Regulatory Τ‐cell Differentiation Between Maternal and Cord Blood Samples in Pregnancies with Spontaneous Vaginal Delivery and with Elective Cesarian Section

Citation Bili H, Fleva A, Pados G, Argyriou T, Tsolakidis D, Pavlitou A, Tarlatzis BC. Regulatory T‐cell differentiation between maternal and cord blood samples in pregnancies with spontaneous vaginal delivery and with elective cesarian section. Am J Reprod Immunol 2011; 65: 173–179 Problem The immunological mechanisms preventing fetal antigenic rejection during normal pregnancy and the extent to which the type of delivery influences lymphocyte reactions are elusive. Method of study Maternal peripheral blood and neonatal umbilical cord blood (CB) was collected upon labor after vaginal delivery or cesarian section. Leukocytes were analyzed with flow cytometry, focusing on regulatory and γ/δ T‐cells. Results In CB from neonates delivered by vaginal delivery, natural killer cells were increased. On the other hand, in maternal blood, γ/δ T‐cells were increased, and activated T‐cells (cluster of differentiation [CD]4+/25^dim/122+ cells) were decreased. Moreover, maternal blood presented increased levels of T regulatory cell subsets like CD4+/25^high/45RO+, CD4+/25^high/DR+, CD4+/25^high/CD38+ and CD4+/25^high/71+. In CB, CD19+, CD4+/25^high/45RA+ and CD4+/25^high/122+ cells were increased. Conclusion The effect of delivery type on lymphocyte immunophenotype was minimal. Mothers’ and neonates’ lymphocyte subsets differed significantly. Mothers’ phenotype comprised significantly of lymphocytes involved in tolerance (memory and activated regulatory T‐cells, γ/δ T‐cells).     

Cytomegalovirus vector expressing RAE‐1γ induces enhanced anti‐tumor capacity of murine CD8+ T cells

Designing CD8⁺ T‐cell vaccines, which would provide protection against tumors is still considered a great challenge in immunotherapy. Here we show the robust potential of cytomegalovirus (CMV) vector expressing the NKG2D ligand RAE‐1γ as CD8⁺ T cell‐based vaccine against malignant tumors. Immunization with the CMV vector expressing RAE‐1γ, delayed tumor growth or even provided complete protection against tumor challenge in both prophylactic and therapeutic settings. Moreover, a potent tumor control in mice vaccinated with this vector can be further enhanced by blocking the immune checkpoints TIGIT and PD‐1. CMV vector expressing RAE‐1γ potentiated expansion of KLRG1⁺ CD8⁺ T cells with enhanced effector properties. This vaccination was even more efficient in neonatal mice, resulting in the expansion and long‐term maintenance of epitope‐specific CD8⁺ T cells conferring robust resistance against tumor challenge. Our data show that immunomodulation of CD8⁺ T‐cell responses promoted by herpesvirus expressing a ligand for NKG2D receptor can provide a powerful platform for the prevention and treatment of CD8⁺ T‐cell sensitive tumors.     

Epitope‐specific CD4+, but not CD8+, T‐cell responses induced by recombinant influenza A viruses protect against Mycobacterium tuberculosis infection

Tuberculosis remains a global health problem, in part due to failure of the currently available vaccine, BCG, to protect adults against pulmonary forms of the disease. We explored the impact of pulmonary delivery of recombinant influenza A viruses (rIAVs) on the induction of Mycobacterium tuberculosis (M. tuberculosis)‐specific CD4⁺ and CD8⁺ T‐cell responses and the resultant protection against M. tuberculosis infection in C57BL/6 mice. Intranasal infection with rIAVs expressing a CD4⁺ T‐cell epitope from the Ag85B protein (PR8.p25) or CD8⁺ T‐cell epitope from the TB10.4 protein (PR8.TB10.4) generated strong T‐cell responses to the M. tuberculosis‐specific epitopes in the lung that persisted long after the rIAVs were cleared. Infection with PR8.p25 conferred protection against subsequent M. tuberculosis challenge in the lung, and this was associated with increased levels of poly‐functional CD4⁺ T cells at the time of challenge. By contrast, infection with PR8.TB10.4 did not induce protection despite the presence of IFN‐γ‐producing M. tuberculosis‐specific CD8⁺ T cells in the lung at the time of challenge and during infection. Therefore, the induction of pulmonary M. tuberculosis epitope‐specific CD4⁺, but not CD8⁺ T cells, is essential for protection against acute M. tuberculosis infection in the lung.     

The choice of adjuvant determines the cytokine profile of T cells in proteoglycan‐induced arthritis but does not influence disease severity

Rheumatoid arthritis (RA) is a debilitating autoimmune disease characterized by chronic inflammation of the synovial joints. Collagen‐induced arthritis (CIA) and proteoglycan‐induced arthritis (PGIA) are mouse models of inflammatory arthritis; CIA is a T helper type 17 (Th17) ‐dependent disease that is induced with antigen in complete Freund's adjuvant, whereas PGIA is Th1‐mediated and is induced using antigen in dimethyldioctadecyl‐ammonium bromide (DDA) as an adjuvant. To investigate whether the type of adjuvant determines the cytokine profile of the pathogenic T cells, we have compared the effect of CFA and DDA on T‐cell responses in a single arthritis model. No differences in incidence or disease severity between aggrecan‐T‐cell receptor transgenic mice immunized with aggrecan in either CFA or DDA were observed. Immunization with CFA resulted in a higher proportion of Th17 cells, whereas DDA induced more Th1 cells. However, the levels of interleukin‐17 (IL‐17) produced by T cells isolated from CFA‐immunized mice after antigen‐specific stimulation were not significantly different from those found in DDA‐immunized mice, indicating that the increased proportion of Th17 cells did not result in significantly higher ex vivo IL‐17 levels. Hence, the choice of adjuvant can affect the overall proportions of Th1 and Th17 cells, without necessarily affecting the level of cytokine production or disease incidence and severity.