TNF blockade induces a dysregulated type I interferon response without autoimmunity in paradoxical psoriasis

Abstract

Although anti-tumor necrosis factor (TNF) agents are highly effective in the treatment of psoriasis, 2-5% of treated patients develop psoriasis-like skin lesions called paradoxical psoriasis. The pathogenesis of this side effect and its distinction from classical psoriasis remain unknown. Here we show that skin lesions from patients with paradoxical psoriasis are characterized by a selective overexpression of type I interferons, dermal accumulation of plasmacytoid dendritic cells (pDC), and reduced T-cell numbers, when compared to classical psoriasis. Anti-TNF treatment prolongs type I interferon production by pDCs through inhibition of their maturation. The resulting type I interferon overexpression is responsible for the skin phenotype of paradoxical psoriasis, which, unlike classical psoriasis, is independent of T cells. These findings indicate that paradoxical psoriasis represents an ongoing overactive innate inflammatory process, driven by pDC-derived type I interferon that does not lead to T-cell autoimmunity.

Fig. 1

Clinical and histological presentation of paradoxical psoriasis. a–c Photographs of cutaneous lesions and corresponding histopathology of three individual patients presenting paradoxical psoriasis. a Patient 1 with small erythemato-squamous plaques disseminated over the entire body resembling guttate psoriasis and palmoplantar psoriasis-like lesions. Histology with a classical psoriasis pattern with acanthosis, papillomatosis, parakeratosis, and loss of the granular layer, but with spongiosis. b Patient 2 with partially crusted, eczematiform lesions on her legs and trunk, palmoplantar psoriasis-like lesions, and severe scalp involvement. Histology with acanthosis, papillomatosis, also in addition to spongiosis and minimal interface dermatitis. c Patient 3 with small erythematous plaques and pustules. Noncicatricial alopecia on the site of scalp involvement. Histology with acanthosis, papillomatosis, and spongiosis. Clinical signs and histopathology of the patients shown are representative of the patient population in this study

Fig. 2

Increased type I interferon in skin lesions of paradoxical psoriasis. a mRNA expression analysis of pro-inflammatory cytokines TNF, IL6, IFNA2, IFNB1, IL36G, IL12A, IL23A, CXCL8, and IL1B relative to GAPDH in skin lesions of paradoxical psoriasis compared to classical plaque psoriasis. b mRNA expression analysis of adaptive T-cell-derived cytokines IL17A, IL17F, IL17C, IL22, IL26, IFNG, IL4, and IL10 relative to GAPDH in skin lesions of paradoxical psoriasis as compared to classical plaque psoriasis. Dots represent individual patient and horizontal bar denotes the median value. Data shown as mRNA expression level relative to mean expression in classical psoriasis (mean value for classical psoriasis was set at 1). Statistical analysis was performed with unpaired non-parametric Mann–Whitney U-test. ND = not detected

Fig. 3

Plasmacytoid dendritic cell (pDC)-derived type I interferon controlled by TNF. a Representative immunohistochemical CD123 (IL3RA)-staining of skin from a patient with paradoxical psoriasis. b Representative confocal laser scanning microscopy of paradoxical psoriasis stained for BDCA2 (CLEC4C) (green), CD123 (red), and DAPI (blue) shows pDCs co-staining for BDCA2 and CD123 (yellow) and CD123 single-positive endothelial cells (*, red). c Histological quantification of CD123-positive pDCs per total dermal infiltrate in skin from healthy donors, psoriasis, and paradoxical psoriasis. d Correlation of numbers of CD123-positive pDCs with gene expression of IFNA2. e IFN-α produced by pDCs enriched from peripheral blood mononuclear cells of healthy volunteers 48 h after stimulation with DNA/LL37 complexes with or without addition of anti-TNF antibodies. f Relative amount of IFN-α produced by pDCs from healthy volunteers at 48 h, unstimulated or upon stimulation with DNA-LL37 complexes with or without anti-TNF antibodies, with or without addition of TNF. g Relative IFNA2 and TNF mRNA expression by pDCs isolated from healthy volunteers, stimulated with DNA/LL37, and kept in culture for 6, 24, 48, or 72 h, respectively. f Relative IFNA2 mRNA expression by pDCs from healthy volunteers 6, 24, 48, and 72 h upon stimulation with DNA/LL37 complexes either with anti-TNF antibodies or addition of TNF. Dots represent individual patient/healthy donor (c, d) and horizontal bar denotes the mean value (c). Data in f depicted as relative expression (percentage) over amount of IFN-α produced upon stimulation with LL37/DNA (set at 100%); data shown as mean ± SD of six independent experiments with blood from six healthy volunteers (for DNA/LL37 + anti-TNF + TNF; n = 3). Data in g and h depicts one representative of four independent experiments with cells from four different healthy individuals. Statistical analysis was performed in c with unpaired Student’s t-test and in e and f with paired Student’s t-test, in d the Spearman’s rank-correlation coefficient was calculated

Fig. 4

Effect of anti-TNF treatment on plasmacytoid dendritic cell (pDC)-activation in skin. a pDC numbers infiltrating the skin upon mechanical injury of the back of mice treated with or without anti-TNF. pDCs quantified by flow cytometry at indicated time points. b One representative contour plot for each group at indicated time points. c Total skin mRNA expression of the type I interferons Ifna6 and Ifnb1 upon mechanical injury of mice treated with or without anti-TNF at indicated time points. d Expression of co-stimulatory molecules Cd80 and Cd86 on skin-infiltrating pDCs 48 h after mechanical skin injury of mice treated with or without anti-TNF. e Percentage of pDCs infiltrating the skin of mice upon mechanical injury in the presence or absence of anti-TNF and/or anti-IFNAR antibodies. Experiment depicted in a and c is representative for at least three independent experiments using at least three mice per group. Bar charts in d show mean values plus SEM of six mice, with pDCs from skin of two mice pooled for each data point; one representative contour plot for each group (two mice pooled) is depicted in the right panel d. All statistical analyses were performed with unpaired Student’s t-test

Fig. 5

Type I interferon-dependent psoriasis-like skin phenotype induced by anti-TNF. a Quantification of epidermal thickening (acanthosis) in mice treated with or without anti-TNF antibody 7 days after mechanical injury by tape stripping. Representative HE staining (b), immunofluorescence staining for Ki-67 (proliferation, c), and involucrin (differentiation, d) for both untreated and anti-TNF-treated mice 7 days after mechanical injury. e Quantification of acanthosis 7 days after mechanical injury of mice treated with or without anti-TNF, and with or without anti-IFNAR antibodies. f Representative HE staining of skin 7 days after mechanical injury of untreated mice and mice treated with anti-TNF antibody alone or anti-TNF and anti-IFNAR antibodies combined. Experiment depicted is representative for at least three independent experiments. Scale bars represent 50 μm. Dashed line b–d and f represents border between epidermis above and dermis below. All statistical analyses were performed with unpaired Student’s t-test. Anti-IFNAR = anti-type I interferon receptor antibody

Fig. 6

T-cell-independent induction of paradoxical psoriasis. a Quantification of acanthosis 7 days after mechanical injury of wild-type mice, wild-type mice treated with anti-TCRβ antibody, and Rag2 ^−/− mice, all of which were treated with or without anti-TNF antibody. b Representative HE staining of skin 7 days after mechanical injury of mice treated with anti-TCRβ antibody alone or anti-TCRβ and anti-TNF antibodies combined. c Representative HE staining of skin 7 days after mechanical injury of Rag2 ^−/− mice treated with or without anti-TNF antibody. d Number of epidermal CD8⁺ T cells per high-power field in skin lesions of patients with classical psoriasis and paradoxical psoriasis. e, f Representative CD8 staining of paradoxical psoriasis (e) and classical psoriasis (f). g Number of dermal LAMP3⁺ cells per high-power field in skin of healthy donors as well as in skin lesions of patients with classical psoriasis and paradoxical psoriasis. h, i Representative LAMP3-staining of paradoxical psoriasis (h) and classical psoriasis (i). Experiment depicted (in a–c) is representative for two independent experiments. Bar charts in a show mean values plus SEM of five mice each group. Dashed line in b, c, e, f, h, and i represents border between epidermis above and dermis below. Arrows point at intraepidermal CD8⁺ T cells in paradoxical psoriasis (e) or dermal LAMP3⁺ cells (h), respectively. All statistical analyses were performed with unpaired Student’s t-test. Anti-TCRβ = anti-T-cell receptor beta chain antibody