Reduction of skin-homing cytotoxic T cells (CD8+ -CLA+) in patients with vitiligo

Background: Vitiligo is a frequently acquired, hereditary disease, characterized by achromic macules due to the absence of melanocytes. In contrast with earlier studies, in which the main pathogenic role was attributed to anti‐melanocyte antibodies, recent papers have emphasized a role for CD8⁺ cytotoxic T lymphocytes in melanocyte destruction. Fifteen percent of peripheral T cell express cutaneous lymphocyte‐associated antigen (CLA), responsible for skin‐homing T cell. Phototherapy is used to treat patients with generalized vitiligo and it has been shown to interfere with CLA⁺ T cells in other skin diseases. Objective: To describe peripheral blood T cell subpopulations' frequency and ability to express the skin‐homing molecule (CLA) in patients with non‐segmental vitiligo, before and after photochemotherapy (PUVA). Patients and Methods: Twenty‐two patients with generalized and active spreading vitiligo were submitted to 30 PUVA‐8MOP sessions. Lymphocyte immunophenotyping was performed by flow cytometry using anti‐CD3, anti‐CD8 and anti‐CLA monoclonal antibodies. Fifteen healthy volunteers, sex‐ and age‐matched, were included as a control group. Results: CD8⁺–CLA⁺ T cells were significantly reduced in number in untreated vitiligo patients (P=0.008) when compared with control individuals, albeit with a more intense CLA expression (P=0.028). These findings were not altered after PUVA. No significant difference was noticed in CD4/CD8 ratios nor in CD4–CLA⁺ T cell numbers between vitiligo patients and controls, both before and after PUVA. Conclusions: CD8–CLA⁺ T cells are reduced in peripheral blood of patients with non‐segmental vitiligo. This finding may be related to the previously reported increase of CD8⁺ cells in both lesions and perilesional skin of these patients.     

1,24‐Dihydroxyvitamin D3 (tacalcitol) prevents skin T‐cell infiltration

Background 1,24‐Dihydroxyvitamin D₃ (tacalcitol), a vitamin D₃ compound, has been used to treat T cell‐mediated inflammatory skin diseases such as psoriasis, prurigo and vitiligo. The best‐known mechanism of action of this compound is inhibition of the abnormal proliferation of keratinocytes and subsequent maturation; however, its effects on skin T‐cell recruitment have not yet been evaluated. Cutaneous lymphocyte‐associated antigen (CLA), a surface glycoprotein expressed on T cells, plays a critical role in skin T‐cell infiltration. We recently reported that 1,25‐dihydroxyvitamin D₃ inhibits skin infiltration of CD4+ T cells by suppressing CLA expression on T cells. Objectives In this study, we investigated the effect of tacalcitol on CLA epitope decoration and on the levels of gut or lymph node homing receptor expression in human T cells. Methods We cultured human T cells with tacalcitol and analysed the effect on CLA expression and skin‐homing ability, and evaluated glycosyltransferase mRNAs. We also performed an in vivo study using an antigen‐dependent delayed‐type hypersensitivity (DTH) mouse model and investigated the effect of tacalcitol on skin‐infiltrating CD4+ T cells. Results Tacalcitol downregulated the expression of CLA and, in parallel, the E‐ and P‐selectin ligand function; however, it exerted no effect on other homing receptors. Subcutaneously and intraperitoneally administered tacalcitol downregulated skin infiltration of effector CD4+ T cells in an in vivo DTH mouse model. Conclusions These findings suggest that tacalcitol reduces skin inflammation by partially downregulating CLA expression levels.     

寻常型银屑病皮肤中皮肤归巢T细胞免疫组化研究

目的 探讨皮肤归巢T细胞在寻常型银屑病(PV)发病中的作用。方法 采用间接免疫荧光双标法研究正常人皮肤和PV患者皮肤中浸润的皮肤归巢T细胞分类及其变化。结果 ①正常人皮肤及PV皮损中浸润的T细胞绝大多数表达皮肤淋巴细胞相关抗原(CLA),CLA⁺细胞高度表达CD45RO,只有个别为CD45RO阴性。②进行期皮损CD4⁺CLA⁺及CD8⁺CLA⁺T细胞数高于静止期皮损(P<0.05),静止期皮损CD4⁺CLA⁺细胞数高于消退期皮损(P<0.05),消退期皮损CD8+CLA+细胞数高于PV外观正常皮肤(P<0.05),进行期皮损周边外观正常皮肤CD4⁺CLA⁺及CD8⁺CLA⁺细胞数高于静止期皮损周边外观正常皮肤(P<0.05).③部分病例皮损的表皮中见大量CLA⁺树突状细胞,正常人皮肤未见此细胞。结论 正常人皮肤及PV皮损中T细胞绝大多数为皮肤归巢T细胞;进行期及静止期PV皮损中浸润的细胞主要为CD3⁺、CD4⁺、CD45RO⁺、CLA⁺T细胞,CD3⁺、CD4⁺、CD45RO⁺、CLA⁺T细胞可能在PV发病中起重要作用。     

Sun exposure induces rapid immunological changes in skin and peripheral blood in patients with psoriasis

Background Ultraviolet (UV) radiation has immunosuppressive effects and heliotherapy is a well‐described treatment modality for psoriasis. Objectives To characterize early sun‐induced immunological changes both local and systemic in patients with psoriasis. Methods Twenty patients with moderate to severe psoriasis were subjected to controlled sun exposure on Gran Canaria, Canary Islands, Spain. Psoriasis Area and Severity Index (PASI) scores were evaluated. Skin biopsies were obtained from lesional and nonlesional skin in 10 patients at baseline and on day 16 and from five additional patients on day 2. Specimens were examined with immunohistochemistry and polymerase chain reaction. Blood samples were obtained from all patients at the same time points and were examined for T‐cell subsets and cytokine production. Results Significant clinical improvement was achieved during the study period. CD4+ and CD8+ T cells in lesional skin were significantly reduced in both the epidermis and dermis. In contrast, dermal FOXP3+ T cells were relatively increased. In the peripheral blood skin homing cutaneous lymphocyte‐associated antigen (CLA)+ T cells were significantly decreased after only 1 day in the sun and in vitro stimulated peripheral blood mononuclear cells demonstrated reduced capacity to secrete cytokines after 16 days. Conclusions Our data show that clinical improvement of psoriasis following sun exposure is preceded by a rapid reduction in local and systemic inflammatory markers, strongly suggesting that immune modulation mediated the observed clinical effect. We cannot completely rule out that other mechanisms, such as stress reduction, may contribute, but it is extensively documented that UV irradiation is a potent inducer of immunosuppression and we therefore conclude that the observed effect was primarily due to sun exposure.     

Circulating CLA+ T cell subsets inversely correlate with disease severity and extension in acute psoriasis but not in chronic plaque psoriasis

Circulating CLA+ T cells represent a subset of lymphocytes functionally associated to several cutaneous diseases. This population of peripheral lymphocytes is poorly characterized in acute stage psoriasis. We studied, by flow cytometry, the relationship between disease severity and extension and different subsets of circulating T cells in 31 psoriatic patients (7 guttate, 8 acute and 16 chronic psoriasis). An inverse correlation between circulating CLA+ CD3+/CD4+ subsets and disease severity and extension was found in the acute form of psoriasis. Interestingly, we also observed that circulating CLA+CD4+CD25+ cells inversely correlated with PASI and BSA in guttate patients, which had not been shown previously. These results may contribute to clarify the role of circulating T cells in psoriasis, especially in early stages of psoriasis.     

8-Methoxypsoralen plus UVA treatment increases the proportion of CLA+ CD25+ CD4+ T cells in lymph nodes of K5.hTGFβ1 transgenic mice

Abstract: 8‐Methoxypsoralen plus UVA (PUVA) photochemotherapy is an effective treatment for many skin diseases including psoriasis. However, its exact mechanism of therapeutic action is incompletely understood. Previously, in K5.hTGFβ1 transgenic psoriatic mice, we found that PUVA induces Foxp3+ CD25+ CD4+ regulatory T cells in both lymph node and spleen. Now, in the same model, we investigated whether cutaneous lymphocyte‐associated antigen (CLA) mediates PUVA’s effect on homing of CD25+ CD4+ T cells to the lymph nodes of K5.hTGFβ1 transgenic mice. We found that a low dose of topical PUVA maximally increased the proportion of CLA + CD25+ CD4 + T cells in the lymph nodes by up to 8‐fold. We also observed an increased number of Foxp3+ CD25+ T cells in the skin of the mice after PUVA treatment. Together, these findings suggest that PUVA affects the homing of regulatory T cells.     

Relevance of compartmentalization of T-cell subsets for clinical improvement in psoriasis: effect of immune-targeted antipsoriatic therapies

Background Therapies targeting the T cell‐mediated pathology of psoriasis have been found to achieve remarkable clinical improvement and have confirmed the crucial role of the immune system either in peripheral blood (PB) or in skin. No analyses of T‐cell counts in both compartments have been conducted in order to confirm or refute the hypothesized shifts between them. Objectives To gain more insight in the dynamics of compartmentalization of T cells between PB and lesional skin of patients with psoriasis, in response to immune‐targeted antipsoriatic therapies. Methods Eighteen patients with psoriasis received either efalizumab (n = 9) or etanercept (n = 9) for 12 weeks. Biopsies were taken for immunohistochemical analysis of T‐cell subsets and simultaneously T‐cell subsets were isolated from PB specimens by flow cytometry. Results The Psoriasis Area and Severity Index declined significantly after 12 weeks of etanercept, but not for efalizumab. After treatment with efalizumab, a significantly decreased number of all T‐cell subsets was found in the dermis. In the epidermis, CD4+, CD8+, CD25+, CD45RO+ and CD161+ T‐cell subsets were significantly decreased. With respect to etanercept, few significant changes in T‐cell subsets were found. The percentage of lymphocytes in PB was significantly elevated after efalizumab treatment regardless of responder status. Conclusions Treatment with efalizumab establishes successful recompartmentalization of T‐cell subsets with modest clinical efficacy after 12 weeks, whereas in etanercept‐treated patients, a significant clinical response is no guarantee for significant changes in T‐cell subsets in the different compartments. Reductions in T‐cell subsets cannot be used as predictive markers for the clinical response to therapy. Interference with the studied T‐cell populations in its own right seems not to be responsible for the clinical efficacy of efalizumab and etanercept.     

Immunophenotyping of inflammatory cells in subacute prurigo

Background Subacute prurigo (SP) is a relatively common disease of papular cutaneous lesions that itch intensely. However, there is a lack of systematic clinical and histological studies on SP. Objectives We aimed to immunophenotype inflammatory cells in SP using immunohistochemistry and flow cytometry. Methods Lesional and non‐lesional skin of 21 patients with SP was investigated. Immunohistochemical staining for CD1a, CD3, CD4, CD8, CD15, CD34, CD68, and anti‐human tryptase (AHT) was performed. In order to evaluate the absolute counts and percentages of CD4+ and CD8+ lymphocytes in the peripheral blood of SP patients, flow cytometric methods were used. Results Compared to non‐lesional skin, there was a significant increase of the median percentage of CD3+, CD4+, and CD8+ cells in the lesional dermis (12.6% vs. 19.7%, P = 0.044; 0.8% vs. 3.7%, P = 0.016; and 1% vs. 15.6%, P = 0.0039, respectively). The mean ± SD CD4+/CD8+ ratio was 0.58 ± 0.6. Median percentage of CD15+ cells was significantly increased in lesional skin as compared to non‐lesional skin (11.7 vs. 1%, P = 0.027). Median percentage immunoreactivity of CD68+ cells was significantly increased in lesional dermis as compared to non‐lesional skin (32.5% vs. 9.4%, P = 0.0005). CD1a, CD34, and AHT positive cells did not significantly differ between lesional and non‐lesional skin. T lymphocyte subsets in the peripheral blood of SP patients did not show significant pathologies. Conclusions We observed that the inflammatory cell infiltrate in SP mainly consists of T lymphocytes, particularly CD8+ cells, CD15+ neutrophils, and CD68+ macrophages.     

流式细胞术双色免疫荧光标记观察寻常性银屑病患者外周血淋巴细胞亚群

目的了解寻常性银屑病患者外周血淋巴细胞亚群的变化。方法应用流式细胞仪双色免疫荧光标记,检测98例寻常性银屑病患者外周血淋巴细胞亚群并与102名正常人进行比较。结果银屑病患者外周血CD4+细胞百分数显著高于正常人对照组(P<0.05);NK细胞百分数显著低于正常人对照组(P<0.01),寻常性进行期银屑病患者T细胞和CD4+细胞显著高于静止期银屑病患者(P<0.05),进行期银屑病患者T细胞、B细胞、CD4+细胞百分数均显著高于正常人对照组(P<0.001),NK细胞显著低于正常人对照组(P<0.001)。静止期银屑病患者与正常人对照组相比淋巴细胞亚群各项指标无明显差异。结论寻常性银屑病患者外周血淋巴细胞亚群的变化主要表现在T、B淋巴细胞特别是CD4+细胞的升高和NK细胞的降低。     

An unexpected twist in alopecia areata pathogenesis: are NK cells protective and CD49b+ T cells pathogenic?

Please cite this paper as: An unexpected twist in alopecia areata pathogenesis: are NK cells protective and CD49b+ T cells pathogenic? Experimental Dermatology 2010; 19 : e347–e349. Abstract: Natural killer (NK) cells have become a recent focus of interest in alopecia areata (AA) research. To further investigate their role in an established mouse model of AA, lesional skin from older C3H/HeJ mice with AA was grafted to young C3H/HeJ female mice, and NK cells were depleted by continuous administration of rabbit anti‐asialo GM1. As expected, this significantly reduced the number of pure NK cells in murine skin, as assessed by NKp46 quantitative immunohistochemistry. Quite unexpectedly, however, the onset of hair loss in C3H/HeJ mice was accelerated, rather than retarded. NK cell depletion was accompanied by a significant increase in the number of perifollicular CD49b+T cells in the alopecic skin of anti‐asialo GM1‐treated mice. These findings underscore the need to carefully distinguish in future AA research between pure NK cells and defined subsets of CD49b+ lymphocytes, as they may exert diametrically opposed functions in hair follicle immunology and immunopathology.     

The effects of ultraviolet B treatment on the expression of adhesion molecules by circulating T lymphocytes in psoriasis

BACKGROUND: T lymphocytes are believed to play a role in the pathogenesis of psoriasis; > 80% of T lymphocytes that infiltrate psoriatic lesions express the surface glycoprotein cutaneous lymphocyte-associated antigen (CLA), compared with < 20% in the blood. Exposure to ultraviolet (UV) B is an effective treatment for psoriasis. OBJECTIVES: To compare the effects of UVB treatment of psoriasis on the expression of CLA and several other surface markers expressed by circulating T lymphocytes. METHODS: Peripheral blood mononuclear cells from psoriatic patients were stained for adhesion molecules and stimulated with streptococcal antigens before and once weekly during 3 weeks of UVB treatment. RESULTS: A marked and progressive decrease was observed during the treatment in expression of the CLA and the very late antigen-4alpha by T cells; this decrease correlated closely with clinical improvement (Psoriasis Area and Severity Index). T-cell expression of intercellular adhesion molecule-1 was not significantly affected during the treatment and no change was observed in the activation markers CD25 and CD69 or lymphocyte proliferation after stimulation with streptococcal antigens or superantigens. CONCLUSIONS: UVB treatment is associated with a marked reduction in the expression of skin-homing molecules by circulating T cells. This may be relevant to the therapeutic effect of UVB in psoriasis.     

银屑病患者皮损及非皮损部位粘附分子免疫组化研究

目的　为了更好地了解浸润 T淋巴细胞和内皮细胞粘附分子的原位表达在银屑病皮损中的相互关系。方法　采用免疫组化染色方法研究银屑病皮损部位和非皮损部位的浸润 T淋巴细胞亚群和内皮细胞粘附分子 (ICAM- 1,EL AM- 1,VCAM- 1)的原位表达情况。结果　银屑病患者皮损部位 T细胞亚群和内皮细胞粘附分子的原位表达均显著高于非皮损部位 ,而且浸润 T淋巴细胞亚群的细胞密度和内皮细胞粘附分子的原位表达程度呈显著正相关。与正常人相比 ,银屑病非皮损部位和经外用皮质类固醇激素治疗后外观正常的皮肤内皮粘附分子仍呈上调表达。结论　银屑病患者皮肤真皮血管内皮细胞粘附分子的异常上调表达是造成银屑病复发的原因之一。     

Reduced CD26bright expression of peripheral blood CD8+ T-cell subsets in psoriatic patients

Abstract: Background: T cells have been shown to be highly relevant in psoriasis. CD26 is a novel T‐cell activation marker involved in various T‐cell functions, e.g. (i) co‐stimulation, (ii) migration and (iii) T‐cell memory response. In particular, CD26bright peripheral blood T cells have been shown to be altered in several autoimmune diseases. Objective: To characterize CD26‐expression of T‐cell subsets in psoriatic patients compared to healthy subjects. Methods: Peripheral blood was obtained from 15 untreated patients with severe psoriasis and from nine healthy subjects. The presence of specific CD26‐related T‐cell subsets was assessed by flow cytometry. Results: The CD26bright expression of CD8+ lymphocytes revealed a statistically significant (P<0.05) decrease in psoriatic patients. The majority of CD4+CD26bright cells are CD45RO+, whereas the minority of CD8+CD26bright cells are CD45RO+ in both groups. Conclusions: The present study demonstrates that the CD8CD26bright T‐cell population is markedly decreased in peripheral blood of psoriatic patients. Moreover, CD26 expression did not show a restriction to memory T cells. As CD26 is of relevance for T‐cell functions, future investigations should focus on elucidating these functions in psoriasis. It is attractive to speculate that the reduction in the CD8CD26bright subpopulation may represent a biomarker for recompartimentalization of activated T cells and a reduced CD8CD26bright count may correlate with increased responsiveness to T‐cell targeted treatments.     

Skin-homing T lymphocytes: detection of cutaneous lymphocyteassociated antigen (CLA) by HECA-452 in normal human skin

The immigration of circulating T cells into specific tissues is directed by the interaction between adhesion molecules on lymphocyte subpopulations and their ligands on vascular endothelium. Of these, endothelial leucocyte adhesion molecule (ELAM-1), weakly expressed in normal human skin (NHS), seems to be the counter-structure for cutaneous lymphocyte-associated antigen (CLA). CLA is a 200 kDa cell-surface glycoprotein of which the sugar moieties sialyl Le(a) and sialyl Le(x) are the possible epitopes recognized by the monoclonal antibody HECA-452. HECA-452 was originally described as a marker for lymphoid organ high endothelial cells, but 16% of peripheral-blood-derived T cells react with this antibody. We studied the expression of CLA on the cellular constituents of the skin immune system (SIS). By applying immunohistochemical double staining, 41% of CD3+ T cells, 44% of CD4+ T cells and 31% of CD8+ T cells were found to express CLA. Keratinocytes, CD1a+ Langerhans cells (LC) and endothelial cells did not express HECA-452 in significant numbers in NHS. Monocytes were found to express HECA-452 in 14% of CD68+ cells. CLA expression was present on a relatively low percentage of T cells and subsets localized distant from NHS vessels, suggesting loss of the molecule during further migration after transendothelial passage. However, intraepidermal T cells expressed CLA in similar percentages to T cells localized directly perivascularly. Our findings support the notion that CLA expression by T cells is associated with their homing into cutaneous structures.     

Memory effector (CD45RO+) and cytotoxic (CD8+) T cells appear early in the margin zone of spreading psoriatic lesions in contrast to cells expressing natural killer receptors, which appear late

BACKGROUND: An influx of immunocytes, increased epidermal proliferation and abnormal keratinization are hallmarks of the psoriatic lesion. T-lymphocyte subsets in particular activated effector memory T cells and natural killer (NK) T cells have been suggested to play an important role in the pathogenesis of psoriasis. OBJECTIVES: In the present study we investigated the number of T-cell subsets (CD4, CD8, CD45RO, CD45RA, CD2, CD25), cells expressing NK receptors (CD94 and CD161), the proliferation marker Ki67 and the keratinization marker keratin (K10) across the margin of the spreading psoriatic plaque: distant uninvolved skin, the outer margin (immediately outside the clinical edge), the inner margin (immediately inside the clinical edge) and the central area. PATIENTS AND METHODS: Eight patients with active psoriasis vulgaris participated in this study. Biopsies were taken from the spreading psoriatic lesion from the distant uninvolved skin, the outer margin, the inner margin and the central area. Biopsies were processed for immunohistochemical staining. RESULTS: In the outer margin CD8+ (cytotoxic T cells) and CD45RO+ (memory effector T cells) T lymphocytes invade the epidermis and in this early stage the activation markers CD2 and CD25 also show a substantial increase. The next phase, from the outer to the inner margin, shows a statistically significant increase of these markers, and especially, the cells expressing NK receptors (CD94 and CD161) show a massive increase together with a significant increase of epidermal proliferation (Ki67) and a decrease of the K10+ epidermal surface. CONCLUSIONS: CD8+, CD45RO+, CD2+ and CD25+ T cells have a role in the early phase of the psoriatic process, whereas CD94- and CD161-expressing cells together with epidermal proliferation and keratinization are involved in a later phase.     

Perforin expression is upregulated in the epidermis of psoriatic lesions

BACKGROUND: There are currently very few data regarding the role of cell-mediated cytotoxicity in psoriasis. Both cytotoxic T lymphocytes and natural killer (NK) cells mediate cytotoxicity reactions, mainly by two distinct pathways, the perforin/granzyme and the Fas/Fas ligand pathway. OBJECTIVES: To study the expression and distribution of perforin, T- and NK-cell subsets in psoriatic lesional and nonlesional skin. METHODS: Skin biopsy specimens from both lesional and nonlesional skin of 11 patients with chronic plaque psoriasis and eight healthy controls were analysed by immunohistochemistry. RESULTS: We found a significant increase in CD4+ and CD8+ cells in psoriatic lesions compared with nonlesional and healthy skin. The expression of CD16+ NK cells was significantly lower in lesions compared with healthy skin. Perforin expression was significantly enhanced in the epidermis of psoriatic lesions. CONCLUSIONS: Perforin expression is upregulated in the epidermis of psoriatic lesions, suggesting a potential role for perforin in the creation of the psoriatic plaque.     

Peripheral natural killer cells exhibit qualitative and quantitative changes in patients with psoriasis and atopic dermatitis

Background Psoriasis and atopic dermatitis are the most recurrent skin inflammatory disorders. Despite their distinct aetiology and clinical aspects, these diseases share several immunological features. Besides the largely documented role of T cells, emerging literature supports a potential involvement of innate immune effectors, the natural killer (NK) cells, in both pathologies. In the peripheral blood, NK cells consist of CD3? CD56dim and CD3? CD56bright cell subsets, harbouring a distinct cell surface phenotype, but both endowed with the main NK‐cell effector functions: cytotoxicity and cytokine production. Objectives To determine whether the frequency, the cell surface phenotype and the functional properties of peripheral NK cells were affected in patients with psoriasis or atopic dermatitis. Methods Peripheral blood mononuclear cells were isolated from 11 patients with psoriasis, nine patients with atopic dermatitis and 16 healthy individuals. By using flow cytometry, we analysed the following parameters of peripheral NK cells: the frequency, the cell surface expression of several NK‐cell receptors (NKR) and the activation of the effector functions upon various in vitro stimuli. Results Peripheral NK cells were significantly reduced in both skin diseases. The cell surface expression of various NKR was differently modified in peripheral NK cells of the two cohorts of patients. Finally, NK‐cell natural cytotoxicity was affected only in atopic dermatitis, while interferon‐γ production was defective in both groups of patients. Conclusion Psoriasis and atopic dermatitis are associated with quantitative and qualitative changes of peripheral NK cells, mostly shared by both diseases, supporting a common process implicating these innate effectors in skin inflammation.     

自然杀伤细胞和T淋巴细胞在银屑病发病中作用的研究

用免疫组化法检测10例银屑病患者皮损、皮损周围外观正常皮肤和正常对照组自然杀伤细胞（NK细胞）、T细胞表面抗原的表达。结果表明：患者皮损处真皮乳头NK细胞表面抗原CD16、CD56、CD57、CD94、CD158a，T细胞表面抗原CD2、CD3、CD4、CD8和皮肤白细胞相关抗原（CLA）阳性表达的细胞数，较皮损周围外观正常皮肤和正常对照组增多（P＜0．05或＜0．01）。作者认为：T细胞、NK细胞共同参入银屑病的发病，并分析了二者之间相互关系。     

Cutaneous lymphocyte‐associated antigen as a novel predictive marker of TNF‐alpha inhibitor biological therapy in psoriasis

A considerable number of patients with psoriasis show secondary resistance during long‐term TNF‐alpha inhibitor therapy, necessitating the identification of reliable predictive markers. Predictive role of cutaneous lymphocyte‐associated antigen (CLA) was investigated. Thirty‐eight severe patients with psoriasis were treated for a 24‐week‐long study period. Clinical responsiveness (PASI) and changes in flow cytometry–measured peripheral lymphocyte CLA expression (week 0–2–6) were statistically analysed. Regarding 24‐week‐long treatment outcome patients were divided into two groups: During the first 6 weeks, mean CLA expression showed significant (P = 0.034604) increase among responders (32/38), while after a preliminary increase, it was significantly (P = 0.012539) decreasing in the relapsing group (6/38). Pearson's correlation analysis showed significant negative correlation between PASI and CLA changes. Responders showed (not significantly) lower initial CLA expression than relapsing patients. Our observations suggest change in CLA expression during the first 6 weeks of induction period to serve as a potential predictive marker of TNF‐alpha inhibitor therapy in psoriasis.