Peripheral blood IFN-gamma-secreting Valpha24+Vbeta11+ NKT cell numbers are decreased in cancer patients independent of tumor type or tumor load

Natural killer T (NKT) cells are CD1d-restricted lymphoid cells and are characterized by an invariant T-cell receptor, which in humans consists of a Valpha24 chain paired with a Vbeta11 chain. These cells are known for their rapid production of large amounts of cytokines (e.g., IFN-gamma and IL-4), thereby modulating other cells of the immune system such as T cells, NK cells and dendritic cells. NKT cells have been reported to play important regulatory roles in many immune responses, including antitumor immune responses. Here, we demonstrate an age-dependent decrease in circulating Valpha24(+)Vbeta11(+) NKT cell numbers in both healthy controls and cancer patients and demonstrate that in both groups females have higher NKT cell levels compared to males. In a large group of 120 cancer patients, we show that circulating Valpha24(+)Vbeta11(+) NKT cell numbers are about 50% lower than in age- and gender-matched healthy controls and that this decrease is independent of tumor type or tumor load. This decrease was not restored upon tumor removal by means of surgery or radiotherapy. Even though the percentage of NKT cells that secrete IFN-gamma, as detected by ELISPOT, is normal in cancer patients, the absolute number of circulating IFN-gamma-secreting NKT cells is reduced. Together, our results suggest that the reduced circulating Valpha24(+)Vbeta11(+) NKT cell numbers in cancer patients are not affected by tumor load, but might actually reflect a risk factor for tumor development, e.g., by hampering efficient tumor immunosurveillance.

Circulating Valpha24+Vbeta11+ NKT cell numbers and dendritic cell CD1d expression in hepatitis C virus infected patients

CD1d-restricted natural killer T (NKT) cells are involved in the regulation of various immune responses, and have been shown to inhibit viral replication in animal hepatitis models when activated by the glycolipid alpha-galactosylceramide (alpha-GalCer, KRN7000). Previous studies have indicated that alpha-GalCer-induced activation of the immune system requires both CD1d expression by antigen-presenting cells as well as (normal) numbers of NKT cells. Discrepancies exist over circulating numbers of human invariant Valpha24+Vbeta11+ NKT cells during hepatitis C virus (HCV) infection. Here, by cross-sectional analysis and longitudinal analysis of patients undergoing effective combination antiviral therapy, we demonstrate that circulating Valpha24+Vbeta11+ NKT cell numbers are not decreased during active HCV infection. Importantly, as we also show that CD1d is expressed at comparable levels by peripheral blood monocytes and CD1c+ myeloid dendritic cells (DC) of healthy individuals and HCV-infected patients, these data indicate that all ingredients for evaluating the antiviral effects of the Valpha24+Vbeta11+ NKT cell ligand alpha-GalCer in HCV-infected patients are present.

The immunoregulatory role of CD1d-restricted natural killer T cells in disease

Natural killer T (NKT) cells constitute a T cell subpopulation that shares several characteristics with NK cells. NKT cells are characterized by a narrow T cell antigen receptor (TCR) repertoire, recognize glycolipid antigen in the context of the monomorphic CD1d antigen-presenting molecule, and have the unique capacity to rapidly produce large amounts of both T helper (Th) 1 and Th2 cytokines. Important roles of NKT cells have now been demonstrated in the regulation of autoimmune, allergic, antimicrobial, and antitumor immune responses. Here, we review the immunoregulatory role of NKT cells in disease and discuss NKT cell based immunotherapeutic strategies.

Keratin 8/18 breakdown and reorganization during apoptosis

Monoclonal antibodies that specifically recognize caspase cleaved K18 fragments or specific (phospho)epitopes on intact K8 and K18 were used for a detailed investigation of the temporal and causal relationship of proteolysis and phosphorylation in the collapse of the keratin cytoskeleton during apoptosis. Caspases involved in the specific proteolysis of keratins were analyzed biochemically using recombinant caspases and specific caspase inhibitors. Finally, the fate of the keratin aggregates was analyzed using the M30-ApoptoSense trade mark Elisa kit to measure shedding of caspase cleaved fragments into the supernatant of apoptotic cell cultures. From our studies, we conclude that C-terminal K18 cleavage at the (393)DALD/S site is an early event during apoptosis for which caspase 9 is responsible, both directly and indirectly by activating downstream caspases 3 and 7. Cleavage of the L1-2 linker region of the central alpha-helical rod domain is responsible for the final collapse of the keratin scaffold into large aggregates. Phosphorylation facilitates formation of these aggregates, but is not crucial. K8 and K18 remain associated in heteropolymeric aggregates during apoptosis. At later stages of the apoptotic process, that is, when the integrity of the cytoplasmic membrane becomes compromised, keratin aggregates are shed from the cells.

Differential Expression of Cytokines in UV-B–Exposed Skin of Patients With Polymorphous Light Eruption

BACKGROUND

Disturbances in UV-induced Langerhans cell migration and T helper (T(H)) 2 cell responses could be early steps in the pathogenesis of PLE.

OBJECTIVE

To establish whether UV-B exposure induces aberrant cytokine expression in the uninvolved skin of patients with polymorphous light eruption (PLE).

DESIGN

Immunohistochemical staining and comparison of microscopic sections of skin irradiated with 6 times the minimal dose of UV-B causing erythema and the unirradiated skin of patients with PLE and of healthy individuals.

SETTING

University Medical Center (Dutch National Center for Photodermatoses). Patients Patients with PLE (n = 6) with clinically proven pathological responses to UV-B exposure and normal erythemal sensitivity. Healthy volunteers (n = 5) were recruited among students and hospital staff.

MAIN OUTCOME MEASURES

Expression of cytokines related to Langerhans cell migration (interleukin [IL] 1, IL-18,and tumor necrosis factor [TNF] alpha); T(H)2 responses (IL-4 and IL-10); and T(H)1 responses (IL-6, IL-12, and interferon gamma). Double staining was performed for elastase (neutrophils), tryptase (mast cells), and CD36 (macrophages).

RESULTS

The number of cells expressing IL-1beta and TNF-alpha was reduced in the UV-B-exposed skin of patients with PLE compared with the skin of healthy individuals (P<.05 for TNF-alpha). No differences were observed in the expression of T(H)1-related cytokines but fewer cells expressing IL-4 infiltrated the epidermis of patients with PLE 24 hours after irradiation (P =.03). After UV exposure TNF-alpha, IL-4, and, to a lesser extent, IL-10 were predominantly expressed by neutrophils.

CONCLUSIONS

The reduced expression of TNF-alpha, IL-4, and IL-10 in the UV-B-irradiated skin of patients with PLE appears largely attributable to a lack of neutrophils, and is indicative of reduced Langerhans cell migration and reduced T(H)2 skewing. An impairment of these mechanisms underlying UV-B-induced immunosuppression may be important in the pathogenesis of PLE.

Association of transcription-coupled repair but not global genome repair with ultraviolet-B-induced Langerhans cell depletion and local immunosuppression

Exposure to ultraviolet-B radiation impairs cellular immune responses. This immunosuppression seems to be associated with Langerhans cell migration. DNA damage appears to play a key role because enhanced nucleotide excision repair, a pathway essential for elimination of ultraviolet-B-induced DNA lesions, strongly counteracts immunosuppression. To determine the effect of DNA repair on ultraviolet-B-induced local immunosuppression and Langerhans cell disappearance, three mouse strains carrying different defects in nucleotide excision repair were compared. XPC mice, which were defective in global genome repair, were as sensitive to ultraviolet-B-induced local suppression of contact hypersensitivity to picryl chloride as their wild-type littermates. CSB mice, defective in transcription-coupled repair, were far more sensitive for immunosuppression as were XPA mice, defective in both transcription-coupled repair and global genome repair. Only a moderate depletion of Langerhans cells was observed in XPC mice and wild-type littermates. Ultraviolet-B-induced Langerhans cell depletion was enhanced in CSB and XPA mice. Hence, the major conclusion is that local immunosuppression is only affected when transcription-coupled DNA repair is impaired. Furthermore, a defect in transcription-coupled repair was linked to enhanced ultraviolet-B-induced Langerhans cell depletion. In combination with earlier experiments, it can be concluded that Langerhans cell disappearance is related to ultraviolet-B-induced local but not to systemic immunosuppression.

Polarization of Valpha24+ Vbeta11+ natural killer T cells of healthy volunteers and cancer patients using alpha-galactosylceramide-loaded and environmentally instructed dendritic cells

CD1d-restricted natural killer T (NKT) cells play important regulatory roles in various immune responses. NKT cell-derived T helper (Th) 1 cytokines are important in the induction of antitumor immune responses in mice. Because the CD1d-restricted Valpha24(+) Vbeta11(+) NKT cell population in cancer patients is decreased both in size and in its capacity to secrete IFN-gamma, therapeutic strategies based on reconstitution of type 1 polarized Valpha24(+) Vbeta11(+) NKT cells merit additional investigation. Here, we report the simultaneous strong expansion and type 1 polarization of human invariant Valpha24(+) Vbeta11(+) NKT cells using alpha-galactosylceramide-loaded type 1 dendritic cells and interleukin 15. Type 1 polarized Valpha24(+) Vbeta11(+) NKT cells produced high levels of IFN-gamma, tumor necrosis factor alpha, and granulocyte macrophage colony-stimulating factor, and induced strong cytotoxicity in Jurkat cells in an alpha-galactosylceramide-dependent manner. Importantly, the cytokine profile of Valpha24(+) Vbeta11(+) NKT cells that were initially expanded under Th2 polarizing conditions could be reversed to a Th1 cytokine profile, indicating the plasticity of the cytokine profile of the human adult Valpha24(+) Vbeta11(+) NKT cell population.

Epidermal langerhans cell depletion after artificial ultraviolet B irradiation of human skin in vivo: apoptosis versus migration

Ultraviolet B radiation can suppress cellular immunity. One of the mechanisms related to this immunosuppression is the disappearance of Langerhans cells from the epidermis. The aim of this study was to establish the mechanism of ultraviolet B-induced Langerhans cell disappearance in healthy individuals. The two most likely mechanisms for Langerhans cell disappearance are apoptosis and migration. Apoptosis was assessed in vivo by exposing buttock skin of 10 healthy volunteers to six minimal erythema doses of ultraviolet B. Only very few apoptotic Langerhans cells could be observed in sections from the ultraviolet B-exposed skin. Migration of Langerhans cells cannot be established in skin sections and suction blisters were therefore raised in an attempt to trap migrating Langerhans cells in the sub-basal membrane blister fluid. Blisters were raised on the flexor side of the lower arm of 30 healthy volunteers at several time points after exposure of the skin to six minimal erythema doses of ultraviolet B. Blister fluid was collected and blister roofs were removed to check for Langerhans cell disappearance. Langerhans cells were detected in the blister fluid of the ultraviolet B-exposed skin and not of the unexposed skin. The number of Langerhans cells in the blister fluid peaked at about 18 h after ultraviolet exposure, which coincided with the largest depletion of Langerhans cells in the blister roof. A fraction (20-30%) of the Langerhans cells in the blister fluid stained positive for DNA damage (cyclobutyl pyrimidine dimers), showing that they originated from the epidermis. Ultraviolet B-induced Langerhans cell disappearance appears to be mainly attributable to migration.

Immunocytochemical detection and mapping of a cytokeratin 18 neo-epitope exposed during early apoptosis

A neo-epitope in cytokeratin 18 (CK18) that becomes available at an early caspase cleavage event during apoptosis and is not detectable in vital epithelial cells is characterized. The monoclonal antibody M30, specific for this site, can be utilized specifically to recognize apoptotic cells, which show cytoplasmic cytokeratin filaments and aggregates after immunohistochemistry with M30, while viable and necrotic cells are negative. The number of cells recognized by the antibody increases after induction of apoptosis in exponentially growing epithelial cell lines and immunoreactivity is independent of the phosphorylation state of the cytokeratins. The generation of the M30 neo-epitope occurs early in the apoptotic cascade, before annexin V reactivity or positive DNA nick end labelling. In a flow cytometric assay, the majority of the M30-positive cells appear in the 'apoptotic' subG1 peak. Tests with synthetic peptides define positions 387-396 of CK18, with a liberated C-terminus at the caspase cleavage site DALD-S, as the ten-residue epitope of M30. This epitope starts at the end of coil 2 of the predicted CK18 structure, at a probable hinge region, compatible with the sensitivity to proteolytic cleavage. The definition of a specific caspase cleavage site in CK18 as a neo-epitope can be used for quantification of apoptotic epithelial cells with immunocytochemical techniques and is applicable to both fresh and formalin-fixed material.

Immunocytochemical detection and mapping of a cytokeratin 18 neo-epitope exposed during early apoptosis

A neo-epitope in cytokeratin 18 (CK18) that becomes available at an early caspase cleavage event during apoptosis and is not detectable in vital epithelial cells is characterized. The monoclonal antibody M30, specific for this site, can be utilized specifically to recognize apoptotic cells, which show cytoplasmic cytokeratin filaments and aggregates after immunohistochemistry with M30, while viable and necrotic cells are negative. The number of cells recognized by the antibody increases after induction of apoptosis in exponentially growing epithelial cell lines and immunoreactivity is independent of the phosphorylation state of the cytokeratins. The generation of the M30 neo-epitope occurs early in the apoptotic cascade, before annexin V reactivity or positive DNA nick end labelling. In a flow cytometric assay, the majority of the M30-positive cells appear in the 'apoptotic' subG1 peak. Tests with synthetic peptides define positions 387-396 of CK18, with a liberated C-terminus at the caspase cleavage site DALD-S, as the ten-residue epitope of M30. This epitope starts at the end of coil 2 of the predicted CK18 structure, at a probable hinge region, compatible with the sensitivity to proteolytic cleavage. The definition of a specific caspase cleavage site in CK18 as a neo-epitope can be used for quantification of apoptotic epithelial cells with immunocytochemical techniques and is applicable to both fresh and formalin-fixed material.

Immunocytochemical detection and mapping of a cytokeratin 18 neo-epitope exposed during early apoptosis

A neo-epitope in cytokeratin 18 (CK18) that becomes available at an early caspase cleavage event during apoptosis and is not detectable in vital epithelial cells is characterized. The monoclonal antibody M30, specific for this site, can be utilized specifically to recognize apoptotic cells, which show cytoplasmic cytokeratin filaments and aggregates after immunohistochemistry with M30, while viable and necrotic cells are negative. The number of cells recognized by the antibody increases after induction of apoptosis in exponentially growing epithelial cell lines and immunoreactivity is independent of the phosphorylation state of the cytokeratins. The generation of the M30 neo-epitope occurs early in the apoptotic cascade, before annexin V reactivity or positive DNA nick end labelling. In a flow cytometric assay, the majority of the M30-positive cells appear in the 'apoptotic' subG1 peak. Tests with synthetic peptides define positions 387-396 of CK18, with a liberated C-terminus at the caspase cleavage site DALD-S, as the ten-residue epitope of M30. This epitope starts at the end of coil 2 of the predicted CK18 structure, at a probable hinge region, compatible with the sensitivity to proteolytic cleavage. The definition of a specific caspase cleavage site in CK18 as a neo-epitope can be used for quantification of apoptotic epithelial cells with immunocytochemical techniques and is applicable to both fresh and formalin-fixed material.

Immunocytochemical detection and mapping of a cytokeratin 18 neo-epitope exposed during early apoptosis

A neo-epitope in cytokeratin 18 (CK18) that becomes available at an early caspase cleavage event during apoptosis and is not detectable in vital epithelial cells is characterized. The monoclonal antibody M30, specific for this site, can be utilized specifically to recognize apoptotic cells, which show cytoplasmic cytokeratin filaments and aggregates after immunohistochemistry with M30, while viable and necrotic cells are negative. The number of cells recognized by the antibody increases after induction of apoptosis in exponentially growing epithelial cell lines and immunoreactivity is independent of the phosphorylation state of the cytokeratins. The generation of the M30 neo-epitope occurs early in the apoptotic cascade, before annexin V reactivity or positive DNA nick end labelling. In a flow cytometric assay, the majority of the M30-positive cells appear in the 'apoptotic' subG1 peak. Tests with synthetic peptides define positions 387-396 of CK18, with a liberated C-terminus at the caspase cleavage site DALD-S, as the ten-residue epitope of M30. This epitope starts at the end of coil 2 of the predicted CK18 structure, at a probable hinge region, compatible with the sensitivity to proteolytic cleavage. The definition of a specific caspase cleavage site in CK18 as a neo-epitope can be used for quantification of apoptotic epithelial cells with immunocytochemical techniques and is applicable to both fresh and formalin-fixed material.

CD11b+ cells and ultraviolet-B-resistant CD1a+ cells in skin of patients with polymorphous light eruption

After ultraviolet exposure Langerhans cells (epidermal CD1a+ cells) disappear from the healthy skin, and CD11b+ macrophage-like cells, which are reported to produce interleukin-10, appear in a matter of days. These phenomena are related to the ultraviolet-induced local suppression of contact hypersensitivity reactions. A defect in this suppression might allow inadvertent immune reactions to develop after ultraviolet (over)exposure; i.e., it could cause ultraviolet-B-induced polymorphous light eruption. In order to test this we first exposed buttock skin of eight healthy volunteers to six minimal erythema doses from Philips TL12 lamps, and indeed observed a dramatic disappearance of CD1a+ cells 48 and 72 h later, at which time the number of CD11b+ cells increased in the dermis, and some occurred in the epidermis. The epidermis thickened and showed large defects, filled by CD11b+ cells, just below the stratum corneum. In 10 patients with polymorphous light eruption (five with a normal minimal erythema dose and five with a low minimal erythema dose) CD1a+ cells were present in the epidermis as well as in the dermis before exposure. Strikingly, these cells were still present in considerable number at 48 and 72 h after exposure to six minimal erythema doses. CD11b+ cells already present in the dermis before ultraviolet exposure, increased after ultraviolet exposure, and subsequently also invaded the epidermis. Despite the six minimal erythema doses, there were no apparent defects in the epidermis of the polymorphous light eruption patients. This deviant early response to ultraviolet radiation is likely to be of direct relevance to the polymorphous light eruption and is perhaps useful as a diagnostic criterion.

Immunocytochemical detection and mapping of a cytokeratin 18 neo-epitope exposed during early apoptosis

A neo-epitope in cytokeratin 18 (CK18) that becomes available at an early caspase cleavage event during apoptosis and is not detectable in vital epithelial cells is characterized. The monoclonal antibody M30, specific for this site, can be utilized specifically to recognize apoptotic cells, which show cytoplasmic cytokeratin filaments and aggregates after immunohistochemistry with M30, while viable and necrotic cells are negative. The number of cells recognized by the antibody increases after induction of apoptosis in exponentially growing epithelial cell lines and immunoreactivity is independent of the phosphorylation state of the cytokeratins. The generation of the M30 neo-epitope occurs early in the apoptotic cascade, before annexin V reactivity or positive DNA nick end labelling. In a flow cytometric assay, the majority of the M30-positive cells appear in the 'apoptotic' subG1 peak. Tests with synthetic peptides define positions 387-396 of CK18, with a liberated C-terminus at the caspase cleavage site DALD-S, as the ten-residue epitope of M30. This epitope starts at the end of coil 2 of the predicted CK18 structure, at a probable hinge region, compatible with the sensitivity to proteolytic cleavage. The definition of a specific caspase cleavage site in CK18 as a neo-epitope can be used for quantification of apoptotic epithelial cells with immunocytochemical techniques and is applicable to both fresh and formalin-fixed material.