Persistent activation of CD8+ T-cells characterizes prediabetic twins

Decreased HLA-DQ expression on peripheral blood cells in children with varying number of beta cell autoantibodies

The risk for type 1 diabetes is strongly associated with HLA-DQ and the appearance of beta cell autoantibodies against either insulin, glutamate decarboxylase (GAD65), insulinoma-associated protein-2 (IA-2), or zinc transporter 8 (ZnT8). Prolonged exposure to autoantibodies may be related to T cell exhaustion known to occur in chronic infections or autoimmune disorders. It was hypothesized that autoantibody exposure may affect HLA-DQ expression on peripheral blood cells and thereby contribute to T cell exhaustion thought to be associated with the pathogenesis of type 1 diabetes. The aim of this study was to determine whether autoantibody exposure as an expression of autoimmunity burden was related to peripheral blood cell HLA-DQ cell surface expression in either 1) a cross-sectional analysis or 2) cumulative as area under the trajectory of autoantibodies during long term follow-up in the Diabetes Prediction in Skåne (DiPiS) study. Children (n = 67), aged 10–15 years were analyzed for complete blood count, HLA-DQ cell surface median fluorescence intensity (MFI), autoantibody frequency, and HLA genotypes by Next Generation Sequencing. Decreased HLA-DQ cell surface MFI with an increasing number of autoantibodies was observed in CD16⁺, CD14⁺CD16⁻, CD4⁺ and CD8⁺ cells but not in CD19⁺ cells and neutrophils. HLA-DQ cell surface MFI was associated with HLA-DQ2/8 in CD4⁺ T cells, marginally in CD14⁺CD16⁻ monocytes and CD8⁺ T cells. These associations appeared to be related to autoimmunity burden. The results suggest that HLA-DQ cell surface expression was related to HLA and autoimmunity burden.

•

PBMC HLA-DQ surface expression in beta cell autoimmunity is poorly understood.

•

Children, 10–15 years of age without or with beta cell autoantibodies were analyzed.

•

HLA-DQ cell surface expression decreased with increasing number of autoantibodies.

•

HLA-DQ cell surface expression was related to HLA and autoimmunity burden.

The Immunology of Glaucoma

The presence of specific antibodies and T cells that are specific in patients with glaucoma supports the idea that the immune system may play an important role in the initiation and/or sustainment of glaucomatous optic neuropathy, at least in some patients. At present, our understanding regarding immunological mechanisms associated with glaucomatous optic neuropathy is far from satisfactory. In this review, we examined evidence suggesting involvement of autoimmune responses in the pathogenesis of glaucoma. These include detection of autoantibodies and T cells and expression of cytokines and stress proteins in patients with glaucoma. Although immune responses are thought to be detrimental, some responses may exert a protective effect against neurodegenerative damage. Likely, the balance between positive and negative regulators determines the survival or demise of cells. It is vital that research continues to elucidate the roles of the immune system in glaucomatous neurodegeneration and the possibility of alternative modalities of treatment. These studies may also provide valuable molecular biomarkers for the diagnosis and identification of a specific cohort of patients with glaucoma, that is, those with normal-tension glaucoma.

The type of responder T-cell has a significant impact in a human in vitro suppression assay

Background

In type 1 diabetes (T1D), a prototypic autoimmune disease, effector T cells destroy beta cells. Normally, CD4⁺CD25^+high, or natural regulatory T cells (Tregs), counter this assault. In autoimmunity, the failure to suppress CD4⁺CD25^low T cells is important for disease development. However, both Treg dysfunction and hyperactive responder T-cell proliferation contribute to disease.

Methods/Principal Findings

We investigated human CD4⁺CD25^low T cells and compared them to CD4⁺CD25^- T cells in otherwise equivalent in vitro proliferative conditions. We then asked whether these differences in suppression are exacerbated in T1D. In both single and co-culture with Tregs, the CD4⁺CD25^low T cells divided more rapidly than CD4⁺CD25^- T cells, which manifests as increased proliferation/reduced suppression. Time-course experiments showed that this difference could be explained by higher IL-2 production from CD4+CD25^low compared to CD4+CD25- T cells. There was also a significant increase in CD4+CD25^low T-cell proliferation compared to CD4+CD25- T cells during suppression assays from RO T1D and at-risk subjects (n = 28, p = 0.015 and p = 0.024 respectively).

Conclusions/Significance

The in vitro dual suppression assays proposed here could highlight the impaired sensitivity of certain responder T cells to the suppressive effect of Tregs in human autoimmune diseases.

Activated T cell subsets in human type 1 diabetes: evidence for expansion of the DR+ CD30+ subpopulation in new-onset disease

An important limitation in T cell studies of human autoimmune (type 1) diabetes is lack of direct access to cells infiltrating the pancreas. We hypothesized that cells recently released from the pancreas into the blood might express a characteristic combination of markers of activation. We therefore examined the recently activated circulating T cell population [CD3+, human leucocyte antigen D-related (HLA-DR+)] using cytokine production and 10 additional subset markers [CD69, CD25, CD122, CD30, CD44v6, CD57, CD71, CCR3 (CD193), CCR5 (CD195) or CXCR3 (CD183)], comparing newly diagnosed adult (ND) (age 18-40 years) patients (n=19) to patients with diabetes for >10 years [long-standing (LS), n=19] and HLA-matched controls (C, n=16). CD3+ DR+ cells were enriched by two-step immunomagnetic separation. No differences in basal or stimulated production of interleukin (IL)-4, IL-10, IL-13 or interferon (IFN)-gamma by CD3+ DR+ enriched cells were observed between the different groups of subjects. However, among the CD3+ DR+ population, significant expansions appeared to be present in the very small CD30+, CD69+ and CD122+ subpopulations. A confirmatory study was then performed using new subjects (ND=26, LS=15), three-colour flow cytometry, unseparated cells and three additional subset markers (CD38, CD134, CD4/CD25). This confirmed the expansion of the CD3+ DR+ CD30+ subpopulation in ND subjects. We conclude that a relative expansion in the T cell subpopulation with the activated phenotype CD3+ DR+ CD30+ is seen in the peripheral blood of subjects with newly diagnosed type 1 diabetes. This subpopulation represents less than 0 x 7% of circulating T cells and may provide a rich source of disease-specific T cells that can be isolated from blood.

Lymphocyte sub-populations in gestational diabetes

PROBLEM

We hypothesize that the normal immunologic responses by the maternal immune system during pregnancy are not as well-regulated in gestational diabetes (GD) patients as in healthy pregnant women.

METHOD OF STUDY

Using two-color flow cytometry we evaluated frequencies of peripheral blood lymphocytes in 20 GD patients being treated with insulin; 43 GD patients treated with dietary therapy but no insulin; 44 women experiencing normal pregnancies; and 48 non-pregnant women.

RESULTS

When compared with healthy pregnant women, both GD cohorts showed higher percentages CD4(+)CD25(+) (P < 0.05), CD4(+)CD45RO(+) (P < 0.05) and CD4(+)CD29(+) (P < 0.01) but lower percentages of CD4(+)CD45RA(+) (P < 0.05). Higher percentages of the activated phenotypes CD8(+)CD25(+) and CD8(+)HLA-DR(+) cells in the diet-treated cohort and CD4(+)HLA-DR(+) cells in insulin-treated GB cohort, were observed compared with healthy pregnant subjects (P < 0.05).

CONCLUSIONS

Expanded populations of activated peripheral blood T cells are associated with GD, suggesting that normal maternal immunosuppression is less effective in GD-afflicted women.

T cell homeostasis in tolerance and immunity

The size of the peripheral T cell pool is remarkably stable throughout life, reflecting precise regulation of cellular survival, proliferation, and apoptosis. Homeostatic proliferation refers to the process by which T cells spontaneously proliferate in a lymphopenic host. The critical signals driving this expansion are "space," contact with self-major histocompatibility complex (MHC)/peptide complexes, and cytokine stimulation. A number of studies have delineated an association between T cell lymphopenia, compensatory homeostatic expansion, and the development of diverse autoimmune syndromes. In the nonobese diabetic mouse model of type 1 diabetes, lymphopenia-induced homeostatic expansion fuels the generation of islet-specific T cells. Excess interleukin-21 facilitates T cell cycling but limited survival, resulting in recurrent stimulation of T cells specific for self-peptide/MHC complexes. Indeed, data from several experimental models of autoimmunity indicate that a full T cell compartment restrains homeostatic expansion of self-reactive cells that could otherwise dominate the repertoire. This review describes the mechanisms that govern T cell homeostatic expansion and outlines the evidence that lymphopenia presents a risk for development of autoimmune disease.

Heat shock proteins, immunity and glaucoma

Glaucoma is no longer viewed simply as elevated intraocular pressure (IOP) that damages the optic nerve. In addition to high IOP, evidence is rapidly accumulating that suggests damage to the optic nerve may be initiated or sustained by any number of factors including ischemia, excitotoxicity, neurotrophin insufficiency, peroxynitrite damage or others not yet defined. These different harmful influences then likely act through common final pathways that eventually activate the cellular proteases that accompany neuronal programmed cell death. We believe aberrant immune signal processing may also result in retinal ganglion cell death. We hypothesized that one form of glaucoma may be an autoimmune neuropathy in which an individual's immune system is not only inappropriately regulated, but a cytotoxic effect is rendered by the very system which normally serves to protect it against stress. We propose that the family of proteins termed "heat shock proteins" are critical modulators of both the homeostatic/cytoprotective as well as pathogenic/neurodegenerative arms of the immune system in retinal ganglion cells or glial cells and are thus integral to glaucomatous neurodegeneration.

Evidence from twins for acquired cellular immune hyperactivity in type 1 diabetes

Type 1 diabetes has been associated with an increased frequency of activated T cells and T-cell hyperactivity to non-specific and disease-specific stimuli including the islet autoantigen glutamic acid decarboxylase 65 (GAD). To address whether T-cell hyperactivity is genetic or acquired we measured whole blood cytokines in vitro in response to GAD or tetanus in 18 identical twin pairs, nine discordant for type 1 diabetes. In addition, the activity of 2', 5' oligoadenylate synthetase (OAS) in blood mononuclear cells was measured as a marker of viral infection. Interleukin-2 (IL-2) basally and IL-2 and interferon-gamma (IFN-gamma) in response to GAD, were detected more frequently and at higher levels in diabetic compared to non-diabetic twins. IL-10 was not different between groups. OAS activity was increased in diabetic compared to non-diabetic twins and showed a correlation with basal IL-2 and GAD-stimulated IFN-gamma and IL-10. These findings suggest that T-cell hyperactivity in type 1 diabetes is an acquired trait and could reflect persisting virus expression.

Acute activation of peripheral lymphocytes during treatment of diabetic ketoacidosis

Activated peripheral T-lymphocytes are increased in both pre-insulin-dependent diabetes mellitus (IDDM) patients and in recently diagnosed IDDM patients, as well as in various forms of acute stress. We studied the in vivo T-lymphocyte activation in six patients in severe diabetic ketoacidosis (DKA) prior to treatment, after 24 h of treatment and > or =5 days after admission. Five of the six patients showed an increased percentage of activated T-lymphocytes based on the expression of HLA-DR at 24 h of treatment when compared to the admission percentage of activation (P<.05). There was no correlation to the admission serum glucose, osmolality, or electrolytes. Serum pH showed a trend toward an inverse correlation, but was not statistically significant. We speculate that T-lymphocyte activation plays a role in the progression of the acute complications of subclinical brain edema and interstitial pulmonary edema of DKA. This process could also be another factor in the progression of the chronic complications of IDDM in addition to the well-established effects of hyperglycemia and hypertension.

T cell subsets and sIL-2R/IL-2 levels in patients with glaucoma

PURPOSE

We hypothesize that cellular immunity may have a previously unrecognized role in glaucomatous optic neuropathy. The purpose of this study is to analyze subsets of T cells and the levels of cytokine IL-2 and the soluble IL-2 receptor in peripheral blood from patients with normal pressure glaucoma (NPG) or primary open angle glaucoma (POAG) in comparison to age-matched control subjects.

METHODS

In this study, 38 patients (20 NPG; 18 POAG) and 19 controls were included. sIL-2R and IL-2 were assayed by ELISA. T cell subsets were analyzed by flow cytometry and lymphocyte proliferation was used to measure the reactive ability of T cells to phytohemagglutinin (PHA).

RESULTS

The frequency of CD8(+)HLA-DR(+) lymphocytes were increased in patients with NPG (P = 0.008), and CD3(+)CD8(+) lymphocytes increased in both NPG (P = 0.03) and POAG patients (P = 0.0004). CD5(+) lymphocytes were higher only in POAG patients (P = 0.0012). In comparison to controls, the ratio of CD4(+)/CD8(+) lymphocytes was similar in both groups. The mean concentrations of sIL-2R in NPG (P = 0.011) and POAG (P = 0.0023) patients were higher than that found in control subjects although IL-2 concentrations were similar in these groups. In addition, the reactive ability of T lymphocytes to the non-specific reagent (PHA) was reduced significantly in NPG (P = 0.02) and POAG patients (P=0.04).

CONCLUSION

The alterations of the cellular immune system in patients with glaucoma support our hypothesis that the immune system may play an important role in the initiation and/or sustainment of glaucomatous optic neuropathy in some patients.

Rational design of cytotoxic T-cell inhibitors

This study describes the use of the CD8/major histocompatibility complex (MHC) class I crystal structure as a template for the de novo design of low-molecular-weight surface mimetics. The analogs were designed from a local surface region on the CD8 alpha-chain directly adjacent to the bound MHC class I, to block the protein associations in the T-cell activation cluster that occur upon stimulation of the cytotoxic T lymphocytes (CTLs). One small conformationally restrained peptide showed dose-dependent inhibition of a primary allogeneic CTL assay while having no effect on the CD4-dependent mixed lymphocyte reaction (MLR). The analog's activity could be modulated through subtle changes in its side chain composition. Administration of the analog prevented CD8-dependent clearance of a murine retrovirus in BALB/c mice. In C57BL/6 mice challenged with the same retrovirus, the analog selectively inhibited the antiviral CTL responses without affecting the ability of the CTLs to generate robust allogeneic responses.

Twins: mirrors of the immune system

Twin studies are a powerful tool to assess genetic and nongenetic factors in multifactorial, immune-mediated diseases. Here, Marco Salvetti and colleagues review important results from such studies and highlight their potential value. Future developments that should help to realize the potential of twin studies are discussed.

Role of autoreactive CD8+ T cells in organ-specific autoimmune diseases: insight from transgenic mouse models

There is now convincing evidence that autoreactive CD8+ T cells can contribute to the pathogenesis of organ-specific autoimmune diseases. In the non-obese diabetic mouse, there is direct evidence that beta-islet cell-specific CD8+ cytotoxic T cells have a pathogenic effect. In human diseases such as autoimmune diabetes and multiple sclerosis, indirect evidence also suggests a role for CD8+ T cells in tissue damage, although their antigen specificity is unknown. Transgenic mouse models as well as the use of knockout mice have been instrumental in the identification of the role of autoreactive CD8+ T cells. Spontaneous models of CD8+ T-cell-mediated autoimmunity generated through transgenesis should help delineate the effector mechanisms leading to tissue destruction. The study of autoreactive CD8+ T cells and the characterization of their antigenic specificity should help unravel the pathophysiology of organ-specific autoimmune diseases, help identify exacerbating foreign antigens, and allow the design of antigen-specific immunotherapy targeting the pathogenic autoreactive T cells.

Molecular mechanisms of CD8+ T cell-mediated delayed hypersensitivity: implications for allergies, asthma, and autoimmunity

Delayed-type hypersensitivity (DTH) is defined as the recruitment of T cells into tissues to be activated by antigen-presenting cells to produce cytokines that mediate local inflammation. CD8+ T cells are now known to mediate DTH responses in allergic contact dermatitis, drug eruptions, asthma, and autoimmune diseases. This inflammatory effector capability of CD8+ cytotoxic T cells was previously poorly recognized, but there is now considerable evidence that these diseases may be mediated by CD8+ DTH. The difference between CD8+ T cells and CD4+ T cells mediating DTH relates to the molecular mechanisms by which antigens are processed and presented to the T cells. Antigens external to the cell are phagocytosed and processed for presentation on MHC class II molecules (eg, HLA-DR) to CD4+ T cells. In contrast, internal cytoplasmic antigens are processed by the endogenous pathway for presentation on MHC class I molecules (eg, HLA-A, -B, and -C) to CD8+ T cells. External allergens can also enter the endogenous pathway to be presented to CD8+ T cells. These include many contact sensitizers, chemical and protein respiratory allergens, viral antigens, metabolic products of drugs, and autoantigens. The resulting CD8+ T-cell response explains the role of CD8+ T-cell DTH mechanisms in allergic contact dermatitis, asthma, drug eruptions, and autoimmune diseases.

Increased CD69 and human leukocyte antigen-DR expression on T lymphocytes in insulin-dependent diabetes mellitus of long standing

To better define prevailing activation of circulating T cell subsets in insulin-dependent diabetes mellitus (IDDM) of recent onset (DM; n = 31; median age +/- SD, 28 +/- 6.9 yr) and of long standing (DML; n = 27; age, 33 +/- 10.4 yr; median duration of disease, 105 months), CD4+ and CD8+ T cells were analyzed to determine their naive and memory subsets as well as their expression of human leukocyte antigen (HLA)-DR, interleukin-2 receptor alpha-chain (CD25), and CD69 by three-color flow cytometry. Twenty-six healthy subjects (HS; age, 32.0 +/- 8.2 yr) served as controls. No deviation was seen in either IDDM group compared to HS in CD25 expression on CD4+ or CD8+ cells or in their CD45RA+ or CD45RA- subsets. HLA-DR expression, however, was increased (P < 0.05) in total CD8+ cells and CD45RA+ cells, with CD45RA- CD8+ cells joining the prevailing pattern only in DML. Among CD4+ cells, increased expression of HLA-DR molecules was restricted to total and CD45RA- cells in DML. CD69 expression did not differ between IDDM and HS, but differed between DML (CD4+, CD8+, and CD45RA- CD4+) and DM only. In conclusion, our data demonstrate that HLA-DR expression in IDDM is restricted to memory cells (CD45RA-) among CD4+ cells in DML and is more markedly confined to naive (CD45RA+) than to memory CD8+ cells, whereas the early activation antigen CD69 is more readily expressed in DML than in DM. The observed activation of circulating T cells suggests an ongoing immune process in IDDM both at clinical manifestation and after long duration.

Elevated CD69 expression on naive peripheral blood T-cells in hyperthyroid Graves' disease and autoimmune thyroiditis: discordant effect of methimazole on HLA-DR and CD69

This study investigated T-cell activation markers HLA-DR and CD69 in both naive (CD45RA+) and memory (CD45RA-) CD4+ as well as CD8+ T cells in peripheral blood of patients with autoimmune thyroiditis (AT, N = 28) or hyperthyroid untreated Graves' disease (GDH, N = 34) using three-color flow cytometry. It was demonstrated that patients with AT, but not those with GDH, expressed increased amounts of HLA-DR antigen compared to healthy subjects (HS, N = 26) on total CD4+ (AT: 14.1%; GDH: 11.3%; HS: 10.9%) and CD8+ cells (AT: 31.9%; GDH: 23.5%; HS: 19.4%) as well as on CD45RA- CD4+ cells (AT: 11.2%; GDH: 7.7%; HS: 7.9%). In GDH (+71%) and AT (+91%) only the proportion of HLA-DR+ CD45RA+ CD8+ cells was increased vs HS. Furthermore, euthyroid GD patients on methimazole (GDE, N = 22) displayed greater HLA-DR+ expression on total and CD45RA- cells within both CD4+ (+37 and 40%, respectively) and CD8+ cells (+47 and 93%, respectively) than GDH. In addition, total and CD45RA+ CD4+ and CD8+ cells were increased vs HS. In contrast, proportions of CD69 positive T cells were increased in AT and GDH on total CD4+ (+97 and 74%, respectively) and CD8+ (+95 and 68%, respectively) cells and all subsets thereof (except for CD45RA- cells in GDH), but normalized upon thyrostatic treatment. We conclude that patients with autoimmune thyroid disease harbor an almost twofold greater proportion vs HS of (a) HLA-DR+ CD45RA+ CD8+ T cells, and of (b) CD69 on total CD4+ and CD8+ cells, and an even more marked elevation on their CD45RA+ subset in AT and untreated GD. In addition, (c) thyrostatic treatment by methimazole in GD is accompanied by a further increase in circulating HLA-DR+ CD4+ and CD8+ cells and their CD45RA- subsets, but decreased CD69 expression. These data suggest association of HLA-DR expression with ongoing autoimmunity, while increased CD69 expression relates in part also to elevated thyroid hormone concentration in GDH.