Peripheral immature CD2-/low T cell development from type 2 to type 1 cytokine production

Normal or reactive minor cell populations in bone marrow and peripheral blood mimic minimal residual leukemia by flow cytometry

BACKGROUND

Measurable residual disease (MRD) is a strong independent poor prognostic factor for acute leukemia. Multiparameter flow cytometry (FCM) is a commonly used MRD detection method. However, FCM MRD detection is not well standardized, and the interpretation is subjective. There are normal/reactive minor cell populations in bone marrow (BM) and peripheral blood (PB), which could be confused with MRD.

METHODS

The FCM data of 231 BM and 44 PB pediatric samples performed in a recent 15-month period were retrospectively reviewed. These samples were from 56 B-lymphoblastic leukemia (B-ALL) patients, 11 T-lymphoblastic leukemia (T-ALL) patients, 28 acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) patients, 44 cytopenia/leukocytosis patients, and five patients with mycosis fungoides.

RESULTS

There were over 10 normal or reactive minor cell populations identified with certain phenotypes mimicking MRD of acute leukemia. These mimickers included CD19+ NK cells, CD22+ basophils, CD22+ dendritic cells (DCs), and plasma cells for B-ALL MRD; CD4/8 double-negative T cells, CD4/8 double-positive T cells, cytoplasmic CD3+ NK cells, CD2- T cells, CD7- T cells, CD5- gamma delta T cells, CD56+ NKT cells for T-ALL MRD; CD33+ NK cells, CD117+ NK cells, basophils, plasmacytoid DCs, non-classical monocytes, CD56+ and/or CD61+ monocytes for AML MRD.

CONCLUSIONS

These data confirm the presence of a variety of normal/reactive minor cell populations that could mimic MRD of acute leukemia by FCM. Recognizing these MRD mimickers is important for correct FCM MRD interpretation.

Biomarkers and asthma management: analysis and potential applications

PURPOSE OF REVIEW

Asthma features a high degree of heterogeneity in both pathophysiology and therapeutic response, resulting in many asthma patients being treated inadequately. Biomarkers indicative of underlying pathological processes could be used to identify disease subtypes, determine prognosis and to predict or monitor treatment response. However, the newly identified as well as more established biomarkers have different applications and limitations.

RECENT FINDINGS

Conventional markers for type 2-high asthma, such as blood eosinophils, fraction of exhaled nitric oxide, serum IgE and periostin, feature limited sensitivity and specificity despite their significant correlations. More distinctive models have been developed by combining biomarkers and/or using omics techniques. Recently, a model with a positive predictive value of 100% for identification of type 2-high asthma based on a combination of minimally invasive biomarkers was developed.

SUMMARY

Individualisation of asthma treatment regimens on the basis of biomarkers is necessary to improve asthma control. However, the suboptimal properties of currently available conventional biomarkers limit its clinical utility. Newly identified biomarkers and models based on combinations and/or omics analysis must be validated and standardised before they can be routinely applied in clinical practice. The development of robust biomarkers will allow development of more efficacious precision medicine-based treatment approaches for asthma.

Expression of T-Bet, Eomesodermin, and GATA-3 Correlates With Distinct Phenotypes and Functional Properties in Porcine γδ T Cells

Unlike mice and humans, porcine γδ T cells represent a prominent subset of T cells in blood and secondary lymphatic organs. GATA-3, T-bet and Eomesodermin (Eomes) are transcription factors with crucial functions in T-cell development and functional differentiation, but their expression has not been investigated in porcine γδ T cells so far. We analyzed the expression of these transcription factors in γδ thymocytes, mature γδ T cells from blood, spleen, lymph nodes, and lung tissue as well as in vitro stimulated γδ T cells on the protein level by flow cytometry. GATA-3 was present in more than 80% of all γδ-thymocytes. Extra-thymic CD2⁻ γδ T cells expressed high levels of GATA-3 in all investigated organs and had a CD8α^−/dimCD27⁺perforin⁻ phenotype. T-bet expression was mainly found in a subset of CD2⁺ γδ T cells with an opposing CD8α^highCD27^dim/−perforin⁺ phenotype. Eomes⁺ γδ T cells were also found within CD2⁺ γδ T cells but were heterogeneous in regard to expression of CD8α, CD27, and perforin. Eomes⁺ γδ T cells frequently co-expressed T-bet and dominated in the spleen. During aging, CD2⁻GATA-3⁺ γδ T cells strongly prevailed in young pigs up to an age of about 2 years but declined in older animals where CD2⁺T-bet⁺ γδ T cells became more prominent. Despite high GATA-3 expression levels, IL-4 production could not be found in γδ T cells by intracellular cytokine staining. Experiments with sorted and ConA + IL-2 + IL-12 + IL-18-stimulated CD2⁻ γδ T cells showed that proliferating cells start expressing CD2 and T-bet, produce IFN-γ, but retain GATA-3 expression. In summary, our data suggest a role for GATA-3 in the development of γδ-thymocytes and in the function of peripheral CD2⁻CD8α^−/dimCD27⁺perforin⁻ γδ T cells. In contrast, T-bet expression appears to be restricted to terminal differentiation stages of CD2⁺ γδ T cells, frequently coinciding with perforin expression. The functional relevance of high GATA-3 expression levels in extra-thymic CD2⁻ γδ T cells awaits further clarification. However, their unique phenotype suggests that they represent a thymus-derived separate lineage of γδ T cells in the pig for which currently no direct counterpart in rodents or humans has been described.

Identification of airway mucosal type 2 inflammation by using clinical biomarkers in asthmatic patients

BACKGROUND

The Airways Disease Endotyping for Personalized Therapeutics (ADEPT) study profiled patients with mild, moderate, and severe asthma and nonatopic healthy control subjects.

OBJECTIVE

We explored this data set to define type 2 inflammation based on airway mucosal IL-13-driven gene expression and how this related to clinically accessible biomarkers.

METHODS

IL-13-driven gene expression was evaluated in several human cell lines. We then defined type 2 status in 25 healthy subjects, 28 patients with mild asthma, 29 patients with moderate asthma, and 26 patients with severe asthma based on airway mucosal expression of (1) CCL26 (the most differentially expressed gene), (2) periostin, or (3) a multigene IL-13 in vitro signature (IVS). Clinically accessible biomarkers included fraction of exhaled nitric oxide (Feno) values, blood eosinophil (bEOS) counts, serum CCL26 expression, and serum CCL17 expression.

RESULTS

Expression of airway mucosal CCL26, periostin, and IL-13-IVS all facilitated segregation of subjects into type 2-high and type 2-low asthmatic groups, but in the ADEPT study population CCL26 expression was optimal. All subjects with high airway mucosal CCL26 expression and moderate-to-severe asthma had Feno values (≥35 ppb) and/or high bEOS counts (≥300 cells/mm³) compared with a minority (36%) of subjects with low airway mucosal CCL26 expression. A combination of Feno values, bEOS counts, and serum CCL17 and CCL26 expression had 100% positive predictive value and 87% negative predictive value for airway mucosal CCL26-high status. Clinical variables did not differ between subjects with type 2-high and type 2-low status. Eosinophilic inflammation was associated with but not limited to airway mucosal type 2 gene expression.

CONCLUSION

A panel of clinical biomarkers accurately classified type 2 status based on airway mucosal CCL26, periostin, or IL-13-IVS gene expression. Use of Feno values, bEOS counts, and serum marker levels (eg, CCL26 and CCL17) in combination might allow patient selection for novel type 2 therapeutics.

Asthma and gender impact accumulation of T cell subtypes

BACKGROUND

The "Th2 hypothesis for asthma" asserts that an increased ratio of Th2:Th1 cytokine production plays an important pathogenic role in asthma. Although widely embraced, the hypothesis has been challenged by various empirical observations and has been described as overly simplistic. We sought to establish whether CD3+CD28-mediated and antigen-independent accumulation of type 1 and type 2 T cells differs significantly between nonasthmatic and asthmatic populations.

METHODS

An ex vivo system was used to characterize the regulation of IFN-gamma-producing (type 1) and IL-13-producing (type 2) T cell accumulation in response to CD3+CD28 and IL-2 stimulation by flow cytometry.

RESULTS

IL-13-producing T cells increased in greater numbers in response to antigen-independent stimulation in peripheral blood lymphocytes from female atopic asthmatic subjects compared with male asthmatics and both male and female atopic non-asthmatic subjects. IFN-gamma+ T cells increased in greater numbers in response to either antigen-independent or CD3+CD28-mediated stimulation in peripheral blood lymphocytes from atopic asthmatic subjects compared to non-asthmatic subjects, regardless of gender.

CONCLUSIONS

We demonstrate that T cells from asthmatics are programmed for increased accumulation of both type 2 and type 1 T cells. Gender had a profound effect on the regulation of type 2 T cells, thus providing a mechanism for the higher frequency of adult asthma in females.

Regulation of T cells in airway disease by beta-agonist

It is widely recognized that Th2 cytokines derived from T cells play a major role in the development of allergic lung inflammation that causes most asthma. Beta-agonists are important rescue and maintenance therapies for asthma, yet our understanding of beta-agonist effects on T cell biology is surprisingly poor. Recent studies using both cell culture and more integrative models are beginning to reveal beta-agonist regulation of T cell signaling and function that may be important in the pathogenesis and treatment of asthma and possibly other inflammatory diseases. Here we provide a comprehensive review of the literature concerning beta-agonist effects on T cells, and discuss the relevance of emerging paradigms of beta-adrenergic receptor signaling to T cell function.

The PD-1/PD-L pathway is up-regulated during IL-12-induced suppression of EAE mediated by IFN-gamma

Experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), is mediated by autoantigen-specific T-helper1 (Th1) cells. IL-12, an inducer of Th1 cell development, exerts immunomodulatory effects in EAE. Programmed death-1 (PD-1) and PD-1 ligand (PD-L), new members of the B7 superfamily of costimulatory molecules, play a critical role in regulating EAE. Whether the interaction of IL-12 and the PD-1/PD-L pathway regulates EAE is unclear. We have previously shown that IL-12 suppresses EAE induced by MOG35-55 in C57BL/6 mice, but not in IFN-gamma-deficient mice, suggesting that IFN-gamma is required for the inhibitory effects of IL-12 on EAE. In the current study, PD-L1 expression is up-regulated following IL-12 treatment in wild-type mice, but not in IFN-(-deficient EAE mice. Similarly, IL-12 induces IFN-gamma and PD-L1 expression in cultured MOG-specific T cells from wild-type mice but not from IFN-gamma-deficient mice. Furthermore, PD-L1 expression increased specifically in CD11b+ antigen presenting cells (APCs) after IL-12 administration. These data suggest that one mechanism of IL-12 suppression of EAE is mediated by PD-1/PD-L signaling downstream of IFN-gamma induction in CD11b+ APCs. The regulation of PD-1/PD-L1 may have potential therapeutic effects for EAE and MS.

Beta-agonists modulate T-cell functions via direct actions on type 1 and type 2 cells

Although the beta2-adrenergic receptor (beta2AR) is the most extensively characterized G-protein-coupled receptor (GPCR), the effects of beta-agonists on T-cell subtype function remain poorly understood. In contrast to studies suggesting lack of beta2AR expression on type 2 T cells, we demonstrate that type 2 interleukin-13+ (IL-13+) T cells (CD4+ or CD8+) in human peripheral blood lymphocytes (PBLs) can respond directly to beta-agonist, with effects including induction of protein kinase A (PKA) activity and associated inhibition of CD3-stimulated CD25 expression; CD3-stimulated IL-13, interferon-gamma (IFN-gamma), and IL-2 production; and p38 mitogen-activated protein kinase (MAPK) phosphorylation. PGE2 was more efficacious than beta-agonist in activating PKA and inhibiting cytokine production. beta-agonist and PGE2 also inhibited phorbol myristate acetate (PMA) + calcimycin-stimulated IFN-gamma and IL-2 (but not IL-13) production, suggesting that upstream CD3-initiated signaling is not the sole locus of PKA actions. Differential regulation of PMA-stimulated p38, p42/p44, and NF-kappaB explained the capacity of PGE2 and beta-agonist to inhibit IFN-gamma but not IL-13 production. The inhibition of CD3 + CD28-stimulated IL-13 production by both beta-agonist and PGE2 was reversed at low agonist concentrations, resulting in enhanced IL-13, but not IFN-gamma or IL-2, production. These findings identify direct effects of beta2AR activation on T-cell subtypes and suggest a complex role for GPCRs and PKA activity in modulating T-cell functions.

Human peripheral CD2−/lo T cells: an extrathymic population of early differentiated, developing T cells

We previously reported that a subset of human peripheral blood CD3+ T cells expresses low-to-null CD2 levels (CD2-/lo), produces type 2 cytokines and is inducible to differentiate to functionally mature IFN-gamma+ cells. Multiple-color immunofluorescence analysis indicated that this population, representing <0.1% of the T cells in fresh lymphocytes, contains subsets that are phenotypically immature, including CD4-CD8- and CD3+TCR- cells. Ex vivo, the CD2-/lo cells can proliferate (carboxyfluorescein diacetate succinimidyl ester analysis) independently from exogenous stimulation, respond to CD3-mediated stimulation with significantly greater proliferation than the autologous mature cells and their subsets are inducible to undergo in vitro a developmental sequence similar to that reported for the phenotypically similar thymic populations. This is especially evident for the CD4+CD8+ subset. CD2-/lo T-cell populations exhibit a TCR repertoire (Vbeta chain distribution) that is complete but different (complementarity determining region R3 analysis) from that of the autologous CD2+ T cells. These characteristics distinguish peripheral CD2-/lo T cells as possible early differentiated T cells that may undergo extrathymic maturation, and potentially contribute to maintain the peripheral naive T-cell pool. These findings define the existence of phenotypically immature T cells in the periphery. Also, given the high numbers of CD2-/lo T cells generated, upon ex vivo culture, from peripheral lymphocytes of all adult and neonatal individuals tested, they have relevance to clinical applications for immune reconstitution of T cells, as well as myeloid cells, via myeloid colony-stimulating factors and type 2 cytokines.

Atopy, asthma, and experimental approaches based on the linear model of T cell maturation

The linear model of maturation of IFN-gamma-producing cells from a proliferative pool of type 2 cytokine-producing T cells represents a fundamental shift in interpreting how changes in cytokine production by T cell populations are regulated. A major tenet of this model is antigen-independent, bystander proliferation of type 2 T cells and their maturation to IFN-gamma+ cells. Both clinical observations and prevailing theories of immune system development in asthma are consistent with this highly interpretative in vitro model, which allows unambiguous characterization of the modulation of the intrinsic features of T cell proliferation and differentiation by environmental and genetic factors. Hypotheses based on the linear model of T cell maturation are readily testable and should lead to a greater understanding of not only allergen-specific responses, but also the non-specific, bystander effects associated with specific responses to allergens or pathogens. Topics to be discussed in the context of the linear model of T cell maturation in this review include: (1) allergic responses to an inciting allergen that may enhance sensitivity to subsequent yet different allergens; (2) dampening the preferential accumulation of type 2 T cells during a typical immune response against viral and bacterial pathogens; (3) allergen-independent sensitization in asthmatics: (4) the 'hygiene hypothesis' for the reported increased allergy development in industrialized countries; (5) elevated IFN-gamma levels in asthmatics, in addition to the expected high levels of type 2 cytokines; (6) testing the effects of inflammatory mediators, as well as various anti-inflammation therapies on T cell maturation; and (7) testing the influence of gene variation on T cell maturation.

Peripheral NK cell phenotypes: multiple changing of faces of an adapting, developing cell

We have defined the existence of developmental relationships among human peripheral NK cells with distinct phenotypic and functional characteristics. These findings closely parallel the changes that occur in vivo during NK cell development, and in vitro in experimental culture systems supporting NK cell generation from hematopoietic progenitors. These new insights provide a simplified framework to understand NK cell immunobiology and the cellular bases for their roles in innate immunity, initiation and maintenance of immune responses via regulation of adaptive and accessory cell functions, and immune pathologies.

In vitro modulation of cytokine expression by enkephalin-derived peptides

OBJECTIVE

We have previously reported that low doses of [Met(5)]-enkephalin (YGGFM, met-enkephalin) and two of its derivatives (YGG and YG) enhanced and accelerated delayed-type hypersensitivity responses while much higher doses of these compounds suppressed these reactions. Since the underlying mechanisms by which this and other immunomodulatory effects occur have not been established, this report explores the in vitro modulation of Th1 and Th2 cytokine expression by these peptides.

METHODS

Murine splenocytes were stimulated with suboptimal concentrations of concanavalin A (ConA) in serum-free medium in the absence or presence of met-enkephalin, YGG, YG, [des-Tyr(1)]-met-enkephalin (GGFM), [D-Ala(2)], [D-Met(5)]-enkephalin or tyrosine (Y). Cell-conditioned supernatants were assayed for interferon-gamma (IFN-gamma), interleukin (IL)-2 and IL-4. Relative IFN-gamma and IL-2 mRNA levels were assessed by reverse transcription-polymerase chain reaction. The enhancing and suppressive effects of met-enkephalin and YG on IFN-gamma production were also tested in the presence of naloxone (Nx).

RESULTS

Met-enkephalin, YGG and YG modulated the in vitro production of IFN-gamma in a biphasic manner: stimulation at low doses and inhibition at high doses. At higher concentrations, met-enkephalin and YG also suppressed the production of IL-2 (type 1) and IL-4, a type 2 cytokine. Nx reversed the enhancing effect of met-enkephalin on IFN-gamma production without affecting its suppressive action or any of the immunomodulating effects of YG. The degradation-resistant analog [D-Ala(2)], [D-Met(5)]-enkephalin enhanced IFN-gamma production but did not suppress it.

CONCLUSIONS

YG, the minimal molecular requirement for enhancement and suppression of immune responses by these metabolites, appears to mediate exclusively an across-the-board suppression via low-affinity, nonclassical, nonopioid receptors.

Early administration of IL-12 suppresses EAE through induction of interferon-gamma

Recent findings have shown that IL-12, a key inducer of Th1 cell development, is not required in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) as severe CNS inflammatory demyelination can develop in the absence of IL-12 or IL-12 responsiveness. These data raised the possibility of an immunomodulatory action of IL-12 in this disease model. We show here that IL-12 suppresses MOG35-55-induced EAE in the C57BL/6 mouse when administered during the early induction phase of the disease. The inhibitory effect is interferon-gamma-(IFN-gamma)-dependent, as clearly shown by lack of suppression in IFN-gamma-deficient mice, and is also accompanied by inhibition of mRNA expression of the proinflammatory cytokine IL-17.

The potential role of allergen-specific sublingual immunotherapy in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease associated with increasing prevalence, morbidity, and cost in developed Western countries. Frequently associated with respiratory allergy during adulthood, atopic dermatitis often represents the first phenotypic appearance of atopy in early childhood when the allergic 'march' starts and progressively moves toward food allergy, asthma, and rhinitis. At present, a consistent body of evidence supports the view that atopic dermatitis may represent the skin compartmentalization of a systemic allergic inflammation. Lymphocytes infiltrating early lesional skin express a T helper (Th) 2 pattern of cytokine secretion (increased levels of interleukin [IL]-4 and/or IL-13 and decreased levels of interferon-gamma) as well as the typical Th2-type chemokine receptor CCR4, specific to the thymus and activation-regulated chemokines. Keratinocytes from patients with atopic dermatitis produce thymic stromal lymphopoietin, a novel cytokine that supports the early lymphocyte development in mouse models, and activates dendritic cells involved in the pathogenesis of allergic diseases in humans. Increased levels of circulating hemopoietic precursor cells have been reported in atopic dermatitis, as in allergic asthma and rhinitis. Furthermore, the recognition of CD34+ hemopoietic precursor cells, and evidence for cellular differentiation/maturational events occurring within atopic dermatitis skin lesion infiltrates, are consistent with the recent reinterpretation of the Th2/Th1 paradigm, where Th2 cells appear to belong to the early stages and Th1 to the ultimate stages of a linear, rather than divergent, pattern of lymphoid differentiation. This more detailed understanding of the immunologic derangements contributing to the atopic dermatitis pathogenesis has led to growing interest in allergen-specific immunotherapy for the disease. Due to the complexity intrinsic to atopic dermatitis and the lack of consensus-based guidelines for standardized outcome measure, only eight studies are available in the literature for a qualitative evaluation of this treatment approach. Two of these studies were double blind and placebo controlled, and six were cohort studies. Immunotherapy was found to be effective in one controlled study and five observational reports. Uncertain results were provided by one low-powered, controlled study, and negative outcomes were raised by a unique study performed with oral immunotherapy, which is not an effective route of mucosal allergen administration. Thus, more efficacy studies are required before immunotherapy could be recommended for the routine treatment of atopic dermatitis. Allergen-specific sublingual immunotherapy, given its excellent safety profile and ability to interfere with the systemic aspects of allergic inflammation, appears a good potential candidate for the pathogenetic treatment of the disease.

The IL-12 Signature: NK Cell Terminal CD56+high Stage and Effector Functions

We report that human peripheral NK cells expressing high CD56 levels (CD56(+high)) are terminally differentiated cells indistinguishable from mature NK cells recently activated in the presence of IL-12, and not a functionally distinct NK-cell subset or progenitors to mature CD56(+low) NK cells. CD56(+high) NK cells coexpress all differentiation Ags constitutive or inducible in mature (CD56(+)) NK cells, except CD16, present at lower level than on most mature NK cells. Also, activation markers, activating receptors and adhesion molecules, and most inducible receptors are expressed exclusively and constitutively and are inducible at higher levels on CD56(+high) than on CD56(+low) NK cells. Consistent with their activated phenotype, many CD56(+high) NK cells are cycling and mediate heightened effector functions (proliferation, IFN-gamma and IL-10 but not IL-13 production) in response to IL-12 and other NK cell-specific stimuli. Conversely, IL-12 induces on CD56(+low) NK cells all markers constitutively expressed on the CD56(+high) NK cells, concomitantly preventing the IL-2 (and IL-15)-inducible expression of NKp44 and CD16 re-expression after immune complex-induced down-modulation, and CD56(-/+low) NK cells acquire a CD56(+high) NK cell phenotype in short term in vitro culture with IL-12. The significance of these findings to the NK cell-mediated regulation of immune responses and NK cell development is discussed.

NKT and T cells: coordinate regulation of NK-like phenotype and cytokine production

A maturation-dependent change in phenotype and cytokine production from relatively immature CD161(-) or CD161(+), IL-13(+)IL-4(+), IFN-gamma(-), to mature CD161(+)CD56(+) IFN-gamma(+) cells occurs in primary human alpha-galactosyl ceramide-reactive CD1d-restricted natural killer T (NKT) cells under the control of IL-12 and other monokines. Modulation of this process upon alpha-galactosyl ceramide stimulation explains the opposite roles of NKT cells to drive type 1 and type 2 immune responses. Because the same developmental changes occurred and were similarly regulated in T cells, the data establish that NKT cells should no longer be considered a functionally unique regulatory subset. However, the results of their analysis can be taken as a model for immunotherapeutic approaches with T cells for which a nominal or surrogate antigen is defined.