In Vitro Differentiation from Naive to Mature E-Selectin Binding CD4 T Cells: Acquisition of Skin-Homing Properties Occurs Independently of Cutaneous Lymphocyte Antigen Expression

Molecular Markers Distinguishing T Cell Subtypes With TSDR Strand-Bias Methylation

Human regulatory CD4⁺CD25⁺FOXP3⁺ T cells (Treg) play important roles in the maintenance of self-tolerance and immune homeostasis in various disease settings and are also involved in the suppression of effective immune responses. These cells are heterogeneous in phenotype and function, and the ability to reliably distinguish between various FOXP3-expressing subpopulations can affect the development of successful therapies. This study demonstrates that hypomethylated CpG sites, present in four regions of the FOXP3 locus, CAMTA1 and FUT7 gene regions, can be used to distinguish several subsets of Treg from conventional CD4⁺ T lymphocytes (Tcon) in donors of both genders. We describe a previously unreported strand-bias hemimethylation pattern in FOXP3 promoter and TSDR in donors of both genders, with the coding strand being demethylated within promoter and methylated within TSDR in all CD4⁺ lymphocyte subtypes, whereas the template strand follows the previously described pattern of methylation with both regions being more demethylated in Treg subtypes and mostly methylated in Tcon. This strand-specific approach within the TSDR may prove to be instrumental in correctly defining Treg subsets in health and in disease.

Differing requirements for CCR4, E-selectin, and α4β1 for the migration of memory CD4 and activated T cells to dermal inflammation

CCR4 on T cells is suggested to mediate skin homing in mice. Our objective was to determine the interaction of CCR4, E-selectin ligand (ESL), and α(4)β(1) on memory and activated T cells in recruitment to dermal inflammation. mAbs to rat CCR4 were developed. CCR4 was on 5-21% of memory CD4 cells, and 20% were also ESL(+). Anti-TCR-activated CD4 and CD8 cells were 40-55% CCR4(+), and ∼75% of both CCR4(+) and CCR4(-) cells were ESL(+). CCR4(+) memory CD4 cells migrated 4- to 7-fold more to dermal inflammation induced by IFN-γ, TNF, TLR agonists, and delayed-type hypersensitivity than CCR4(-) cells. CCR4(+) activated CD4 cells migrated only 5-50% more than CCR4(-) cells to these sites. E-selectin blockade inhibited ∼60% of CCR4(+) activated CD4 cell migration but was less effective on memory cells where α(4)β(1) was more important. Anti-α(4)β(1) also inhibited CCR4(-) activated CD4 cells more than CCR4(+) cells. Anti-E-selectin reduced activated CD8 more than CD4 cell migration. These findings modify our understanding of CCR4, ESL, α(4)β(1), and dermal tropism. There is no strict relationship between CCR4 and ESL for skin homing of CD4 cells, because the activation state and inflammatory stimulus are critical determinants. Dermal homing memory CD4 cells express CCR4 and depend more on α(4)β(1) than ESL. Activated CD4 cells do not require CCR4, but CCR4(+) cells are more dependent on ESL than on α(4)β(1), and CCR4(-) cells preferentially use α(4)β(1). The differentiation from activated to memory CD4 cells increases the dependence on CCR4 for skin homing and decreases the requirement for ESL.

Cutaneous lymphocyte-associated antigen (CLA) T cells up-regulate P-selectin ligand expression upon their activation

Memory T cells expressing CLA occur in humans and accumulate in normal and inflamed skin. These cells uniformly bind to the vascular adhesion molecule E-selectin, yet only a subset binds to P-selectin. The latter cells are distinguished by the mAb CHO-131, and are enriched in psoriasis lesions. Activated T cells up-regulate CLA expression, but little is currently known about their binding to P-selectin. We observed that CLA(+) CD4(+) T cells derived from stimulated naive T cells uniformly express the CHO-131 epitope. This occurred as well upon the restimulation of memory CLA(+) CD4(+) T cells. The latter cells also expressed higher levels of PSGL-1 modified by P-selectin glycan ligands; C2GlcNAcT-1 mRNA, a glycosyltransferase critical for such glycan synthesis; and more uniformly bound to P-selectin. Our findings thus indicate that unlike memory CLA(+) CD4(+) T cells, when activated these cells can broadly bind to P-selectin, suggesting a more diverse tissue trafficking capacity.

Defective regulatory T cells in patients with severe drug eruptions: timing of the dysfunction is associated with the pathological phenotype and outcome

Toxic epidermal necrolysis (TEN) and drug-induced hypersensitivity syndrome (DIHS) represent two ends of a spectrum of severe drug eruptions: DIHS is unique in that severe epidermal damage seen in TEN is absent, sequential reactivations of herpesviruses occur, and autoimmunity often ensues. To investigate whether changes in regulatory T (Treg) cell function would contribute to variability in the clinical manifestations, we examined the frequency, phenotype, and function of Treg cells both during the acute stage and again long after clinical resolution of both diseases. Dramatic expansions of functional Treg cells were found in the acute stage of DIHS. In contrast, Treg function was profoundly impaired in TEN, although present in normal frequency. Skin homing addressins were more preferentially expressed on Treg cells in DIHS than in TEN. Indeed, Treg cells were more abundantly present in the skin lesions of DIHS. Surprisingly, Treg cells contracted upon resolution of DIHS became functionally deficient, whereas their functional defects in TEN were restored upon recovery. These findings indicate that a transitory impairment in their function during the acute stage of TEN may be related to severe epidermal damage, while a gradual loss of their function after resolution of DIHS may increase the risk of subsequently developing autoimmune disease.

Varied levels of reactivity by different E-selectin/Fc constructs with cutaneous lymphocyte-associated antigen (CLA)(+) CD4(+) T cells

T cells utilize the vascular adhesion molecule E-selectin to enter inflamed skin. T cells identified by the mAb HECA-452 [cutaneous lymphocyte-associated antigen (CLA) T cells] are enriched in E-selectin ligand expressing cells. However, the proportion of CLA(+) T cells reactive with an E-selectin/Fc chimeric construct, as determined by flow cytometry, can vary considerably between studies. One important variable in these studies has been the E-selectin/Fc chimera used to assess ligand expression. We therefore compared the reactivity of mouse, rat, and human E-selectin/Fc from the same widely used commercial source with peripheral blood CLA(+) CD4(+) T cells, neutrophils, and the promyelocytic cell line HL-60 by flow cytometry and by shear flow assays. We observed that the binding activities of the different E-selectin/Fc chimeras were considerably different. Mouse E-selectin/Fc demonstrated the highest binding activity with human neutrophils and HL-60 cells by both assay approaches, whereas human E-selectin/Fc demonstrated the lowest binding activity. In addition, mouse E-selectin/Fc binding increased essentially in a linear manner with increasing expression of CLA by CD4(+) T cells, whereas human and rat E-selectin/Fc binding occurred with only a subset of CLA(+) CD4(+) T cells. We conclude that there is substantial variability in the reactivity of different E-selectin/Fc constructs, thus caution should be used when assessing E-selectin ligand expression with these reagents. For instance, the discordance in expression of CLA and E-selectin ligands by T cells may in part be due to the E-selectin/Fc construct being used.

Innate immune responses to herpes simplex virus type 2 influence skin homing molecule expression by memory CD4+ lymphocytes

Herpes simplex virus (HSV) infections of humans are characterized by intermittent, lytic replication in epithelia. Circulating HSV-specific CD4 T cells express lower levels of preformed cutaneous lymphocyte-associated antigen (CLA), a skin-homing receptor, than do circulating HSV-specific CD8 T cells but, paradoxically, move into infected skin earlier than CD8 cells. Memory CD4 T cells develop strong and selective expression of CLA and E-selectin ligand while responding to HSV antigen in vitro. We now show that interleukin-12, type I interferon, and transforming growth factor beta are each involved in CLA expression by memory HSV type 2 (HSV-2)-specific CD4 T cells in peripheral blood mononuclear cells (PBMC). A reduction of the number of monocytes and dendritic cells from PBMC reduces CLA expression by HSV-2-responsive CD4 lymphoblasts, while their reintroduction restores this phenotype, identifying these cells as possible sources of CLA-promoting cytokines. Plasmacytoid dendritic cells are particularly potent inducers of CLA on HSV-reactive CD4 T cells. These observations are consistent with cooperation between innate and acquired immunity to promote a pattern of homing receptor expression that is physiologically appropriate for trafficking to infected tissues.

T-cell dynamics of inflammatory skin diseases

The migration of memory T-cells to sites of inflammation is a multistep process controlled by an array of specific receptor-ligand pairs. Chemokines and their receptors represent a central paradigm of the molecular basis of the skin-homing of T-cells. Although CCR4 and CCR10 are both associated with conventionally defined skin-homing T-cells, the association is not necessarily perfect. Interaction between E-selectin and its ligand may represent more specific targets for therapeutic intervention. Although fucosyl transferase?VII is essential for generating E-selectin ligands necessary for T-cell homing to skin, fucosyltransferase-IV, another fucosyltransferase expressed to a significant degree in T-cells, can also generate E-selectin ligands. The induction and upregulation of both enzymes can be co-ordinately regulated depending on their state of activation and differentiation and the cytokine milieu. The dynamic balance between the two enzymes is a major check point for the regulation of skin-homing T-cell differentiation. Polarized T-cells regulate their adhesions on a minute-to-minute basis depending on the cytokine environment. Soluble adhesion molecules found to be increased in chronic inflammatory skin diseases may serve to limit the duration or magnitude of T-cell recruitment. In addition to T-cells migrating from the circulation, T-cells indigenously residing in the tissue itself, such as skin-resident T-cells, would also be responsible for tissue damage. It should also be appreciated that T-cell recruitment to the skin is critical for host defense and that no definitive means exist to distinguish protective regulatory T-cells from pathogenic T-cells.

Trafficking pathways and characterization of CD4 and CD8 cells recruited to the skin of humans experimentally infected with Haemophilus ducreyi

T-cell homing to infected skin is not well studied in humans. We examined sites experimentally infected with Haemophilus ducreyi by immunohistochemistry and flow cytometry for expression of receptors and ligands involved in cutaneous T-cell homing and determined the phenotypes of the T cells that trafficked to skin. Endothelial cells expressed E-selectin in infected but not uninfected skin, while peripheral node addressin (PNAd) was minimally expressed in all samples. CC chemokine ligand 27 (CCL27) was expressed in the epidermis and endothelium of both infected and uninfected skin. Interestingly, CCL21, a chemokine thought to be associated principally with T-cell trafficking in the lymphatic compartment, was highly expressed on the endothelium of infected skin. Few naive cells were present in experimental lesions, emphasizing the combined role of PNAd and CCL21 in trafficking of this subset. Memory cells (CD45RA-) dominated both CD4 and CD8 T-cell populations at the site of infection. Effector memory (CD45RA- CD27-) CD4+ and CD8+ T cells were enriched in lesions. Although the CC chemokine receptor 7-positive (CCR7+) population of both central memory (CD45RA- CD27+) and effector memory cells was not enriched in the skin compared to peripheral blood, CCR7+ cells were not precluded from entering infected skin. Taken together with our previous work (D. Soler, T. L. Humphreys, S. M. Spinola, and J. J. Campbell, Blood 101:1677-1683, 2003), these studies led us to propose a model of memory T-cell trafficking to skin in response to experimental H. ducreyi infection.

Homing in on the cellular immune response to HSV-2 in humans

PROBLEM

Genital herpes simplex infections are generally limited to epithelia and neurons. Vaccines have had activity in herpes simplex virus (HSV)-seronegative women only. Understanding how HSV-specific T cells traffic to infected sites may assist in vaccine design.

METHOD OF STUDY

Herpes simplex virus epitopes recognized by HSV-specific CD8 T cells were identified and used to make fluorescent human leukocyte antigen (HLA)-peptide tetramers. Molecules related to lymphocyte rolling adhesion were studied by flow cytometry and cell binding. HSV-specific CD4 T cells identified ex vivo by cytokine accumulation or activation marker expression, or detected in vitro by 5-(and-6)-carboxyfluorescein diacetate, succinimidyl ester (CFSE) dilution, were similarly investigated.

RESULTS

Herpes simplex virus-specific T cells are 10- to 100-fold more prevalent in lesional skin compared with blood and greatly enriched in lesions compared with normal skin. Diverse viral antigens are recognized by HSV-specific T cells. Functionally active E-selectin ligand, and cutaneous lymphocyte antigen (CLA), are expressed by circulating HSV-2-specific CD8 cells. CD4 cells display lower levels of CLA that are dramatically up-regulated upon re-stimulation with antigen.

CONCLUSIONS

Herpes simplex virus-2-specific CD8 and CD4 T cells differ in constitutive expression of skin homing molecules. Vaccines designed to induce proper homing are postulated to have increased efficacy.

Alpha4beta1 and alpha4beta7 CD4 T cell numbers increase and CLA CD4 T cell numbers decrease in systemic sclerosis

We studied the expression of adhesion molecules affecting recirculation and homing on peripheral blood CD4(+) T cells of patients with systemic sclerosis (SSc), in order to evaluate whether the distribution of tissue targeted subsets could reflect the participation of internal organs or the extent of cutaneous involvement [i.e. limited cutaneous (lc) and diffuse cutaneous (dc)]. Peripheral blood mononuclear cells (PBMC) from 51 patients with SSc and 19 sex- and age-matched controls were investigated by cytofluorimetric analysis for lymphocyte subpopulations carrying the following surface molecules: CD3, CD4, CLA, alpha4beta7 and alpha4beta1. Standard routine biochemistry and clinical examinations were also performed in all patients. We found that both alpha4beta1(+) and alpha4beta7(+) cells within the CD4(+) T cell population were significantly increased, while CLA(+) CD4(+) T cells were significantly reduced in SSc, compared to healthy donors. Significantly lower absolute numbers of alpha4beta7(+) cells were found in lc- compared to dc-SSc. Patients with oesophageal involvement had high numbers of alpha4beta7(+) cells, while those with nephritis also showed low levels of CLA(+) cells. Lung involvement was related directly to alpha4beta1(+) cell numbers and inversely to alpha4beta7(+) CD4 cell numbers. Taken together, our findings demonstrate that distinct CD4(+) T cell populations with selective homing properties show changes from normal distribution in SSc, and such changes are related to clinical expression and organ involvement in the course of the disease.

Expression of cutaneous lymphocyte-associated antigen and E-selectin ligand by circulating human memory CD4+ T lymphocytes specific for herpes simplex virus type 2

Virus-specific memory T lymphocytes traffic to sites of viral infection. Herpes simplex virus (HSV) type 2-specific CD4(+) and CD8(+) T lymphocytes differ with regard to their homing kinetics to infected tissues. We studied the expression of cutaneous lymphocyte-associated antigen (CLA) and E-selectin ligand (ESL) by HSV-2-specific CD4(+) T lymphocytes. Virus-reactive T lymphocytes were identified ex vivo by CD154 or interferon-gamma up-regulation. We detected selective expression of CLA by HSV-2-reactive CD4(+) T lymphocytes, but at levels lower than those we previously observed for CD8(+) T lymphocytes. Short-term HSV-2-reactive CD4(+) lines generated from peripheral-blood mononuclear cells preferentially express CLA, compared with cytomegalovirus- or influenza-specific cells. CLA is expressed by HSV-2-reactive cells that are initially CLA negative before restimulation. Short-term culture-expanded HSV-2-specific CD4(+) T lymphocytes also selectively express ESL. These findings have implications for the optimization of vaccines for HSV and other cutaneous pathogens.