SPRY1 Deficiency in Keratinocytes Induces Follicular Melanocyte Stem Cell Migration to the Epidermis through p53/Stem Cell Factor/C-KIT Signaling.

The function and survival of melanocytes is regulated by an elaborate network of paracrine factors synthesized mainly by epidermal keratinocytes (KCs). KCs and melanocytes respond to UV exposure by eliciting a tanning response. However, how KCs and melanocytes interact in the absence of UV exposure is unknown. In this study, we demonstrate that after SPRY1 knockout in epidermal KCs, melanocyte stem cells in the hair follicle exit the niche without depleting the pool of these cells. We also found that melanocyte stem cells migrate to the epidermis in a p53/stem cell factor/C-KIT-dependent manner induced by a tanning-like response resulting from SPRY1 loss in epidermal KCs. Once there, these cells differentiate into functional melanocytes. These findings provide an example in which the migration of melanocyte stem cells to the epidermis is due to loss of SPRY1 in epidermal KCs and show the potential for developing therapies for skin pigmentation disorders by manipulating melanocyte stem cells.

Biologics protect psoriasis patients from being exacerbated by COVID-19 infection.

Background: Patients with psoriasis may experience an exacerbation in symptoms following COVID-19 infection. After abandoning 'zero COVID' strategies, China experienced a surge of Omicron infections. Objectives: We aimed to investigate psoriasis exacerbation in psoriatic patients with COVID-19, following treatment with three different biologics, adalimumab, secukinumab, and ixekizumab. Methods: We performed a prospective study (n = 209) at our hospital between November 01, 2022, and February 15, 2023. We defined △ PASI as post-COVID-19 PASI minus pre-COVID-19 PASI. Two endpoints were set in this study. △ PASI >0 was defined as exacerbation of psoriasis after infection. △ PASI >3 was defined as a severe exacerbation of psoriasis symptoms after infection. In addition, serum OAS1, OAS2, and OAS3 were also assessed. Results: Results showed that the severity of psoriasis can worsen after COVID-19 infection, and a smaller proportion of patients taking biologics developed worsening psoriasis compared to those not using biologics; however, only the patients taking ixekizumab demonstrated a statistically significant difference (p < 0.05), while those taking adalimumab or secukinumab didn't. What's more, the use of biological agents suppressed the serum OAS2 and OAS3 at low levels and elevated the serum OAS1 level in patients with psoriasis. Conclusions: This study provided new insights into the protective role of biological agents in patients with psoriasis who were infected with COVID-19, and we proposed that psoriatic patients treated with biologics should continue with the treatment during the COVID-19 pandemic.

Glycyl-tRNA Synthetase Induces Psoriasis-Like Skin by Facilitating Skin Inflammation and Vascular Endothelial Cell Angiogenesis.

Psoriasis is characterized by excessive keratinocyte proliferation and immunocyte infiltration, but the underlying pathogenesis remains unclear. Aminoacyl-tRNA synthetases are universally expressed enzymes that catalyze the first step of protein synthesis. Glycyl-tRNA synthetase (GARS) is a member of the aminoacyl-tRNA synthetase family. In addition to its canonical function, we found that GARS was overexpressed in the serum and skin lesions of patients with psoriasis. Moreover, GARS was highly expressed in human skin keratinocytes, and GARS knockdown in keratinocytes suppressed cell proliferation and promoted apoptosis through NF-κB/MAPK signaling pathway. Moreover, intradermal injection of recombinant GARS protein caused skin thickening, angiogenesis, and IFN/TNF-driven skin inflammation. Intriguingly, the reported functional receptor for GARS, cadherin 6 (CDH6), was specifically expressed in vascular endothelial cells, and we found that keratinocyte-derived GARS promotes inflammation and angiogenesis of vascular endothelial cells through CDH6. In addition, intradermal injection of GARS aggravated the phenotype and angiogenesis in imiquimod-induced psoriasiform dermatitis models, whereas the psoriatic phenotype and angiogenesis were relieved after knockdown of GARS by adeno-associated virus. Taken together, the results of this study identify the critical role of GARS in the pathogenesis of psoriasis and suggest that blocking GARS may be a therapeutic approach for alleviating psoriasis.

Epidermal keratinocyte-specific STAT3 deficiency aggravated atopic dermatitis-like skin inflammation in mice through TSLP upregulation.

Atopic dermatitis (AD) is one of the most common inflammatory skin diseases with complex pathogenesis involving epidermal barrier dysfunction, skin microbiome abnormalities and type-2-skewed immune dysregulation. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that plays critical roles in various biological processes. However, the role of STAT3 in epidermal keratinocytes in AD remains unclear. In this study, we generated an epidermal keratinocyte-specific Stat3-deficient mouse strain (termed Stat3 cKO mice). After topical 2,4-dinitrochlorobenzene (DNCB) treatment, Stat3 cKO mice developed worsened AD-like skin inflammation with increased Ki67+ cells, decreased filaggrin and loricrin expression, and downregulated S100A9 and LL37. The dominant microbial population in Stat3 cKO mice changed from Ralstonia to Staphylococcus. DNCB-treated Stat3 cKO mice displayed more infiltrating type-2 inflammatory cells, including mast cells, eosinophils, and CD4+T cells, accompanied by increased skin IL-4 and serum IgE levels. Moreover, thymic stromal lymphopoietin (TSLP), mainly produced by keratinocytes, was highly expressed in the ear skin of Stat3 cKO mice and chemoattracted more TSLPR+ cells. TSLP blockade significantly alleviated DNCB-induced AD-like skin inflammation in Stat3 cKO mice. Thus, epidermal keratinocyte-specific STAT3 deficiency can aggravate AD-like skin inflammation in mice, possibly through TSLP dysregulation.

Keratinoctye-neuro-immune-units (KNICUs): collaborative impact on the initiation and maintenance of psoriasis.

The skin is the outermost barrier that separates the human body from the external environment. In psoriasis, immune cells reside within or infiltrate the epidermis to form the epidermal (epithelial) immunological microenvironment (EIME) and engage in complex interactions with keratinocytes, nerves, and microbiota. The proposed hypothesis is that psoriasis is a chronic inflammatory disease mainly mediated by a specific inflammatory environment composed of keratinocyte-neuro-immune cell units (KNICUs). These KNICUs arise from the interaction between activated epidermal keratinocytes, nerves, immune cells, and the skin microbiota, forming a complex interaction framework. Multiple units gather to complete the circulatory and amplified loops, consequently serving as a group army to initiate and maintain psoriasis.

The epidermal immune microenvironment plays a dominant role in psoriasis development, as revealed by mass cytometry.

Psoriasis is a common chronic inflammatory skin disease. The diversity and heterogeneity of immune cells in human skin have been studied in recent years, but the spatial distribution of immune cells at the single-cell level in the human psoriatic epidermis and dermis remains unclear. In this study, we mapped psoriatic skin immune cells from paired lesional, perilesional, and nonlesional skin samples using mass cytometry. Phenotypic dendritic cells (DCs) were found in the psoriatic epidermis and dermis. Psoriatic dermal CD1c+CD11b+ cDC2s migrated to the epidermis in the perilesional skin during the preinitiation stage. CD1c+CD11b+ cDC2s rapidly replaced EpCAM+CD11clow LC cells and initiated inflammation. Simultaneously, CD207+CD11chi LC and CD5+ T cells accumulated in the psoriatic epidermis and orchestrated epidermal inflammation in psoriasis. The immune cell pool in the psoriatic dermis primarily included APCs and T cells. However, unlike that in the dermis, the epidermal immune environment was more significant and coincided with the inflammation occurring during psoriasis.The epidermal immune microenvironment plays a dominant role in psoriasis. Langerhans cells, epidermis-resident memory T cells and macrophages together contribute to healthy epidermal immune homeostasis. However, psoriatic CD1c+CD11b+ epidermal cDC2s are positioned in the perilesional area, replacing EpCAM+CD11clow LCs rapidly and initiating inflammation. Epidermal CD141+ cDC1s, CD1c+ cDC2s, CD14+ moDCs, and BDCA2+ pDCs orchestrate psoriatic inflammation. Meanwhile, CD11chi LCs and CD5+ T cells accumulate in the psoriatic epidermis.

Mupirocin blocks imiquimod-induced psoriasis-like skin lesion by inhibiting epidermal isoleucyl-tRNA synthetase.

BACKGROUND: The Isoleucyl-tRNA synthetase (IARS) catalyzes isoleucine to the corresponding tRNA, maintaining the accuracy of gene translation. Its role in psoriasis has been not investigated so far. In this study, we aimed to investigate the mechanisms underlying the efficacy of IARS inhibitor, mupirocin, treatment for psoriasis. METHODS: The expression of IARS was determined by immunofluorescence, Western blot and qRT-PCR in normal healthy control- and psoriatic human skin. An imiquimod (IMQ) -induced psoriasis-like skin disease model was used to study the phenotypes changed by an IARS inhibitor, mupirocin (MUP). Endotypes were analyzed by RNA-seq, R&D Luminex multi-factor technique, ELISA, immunofluorescence and flow cytometry. Additionally, the effect of MUP on epidermal keratinocytes (KCs) were conducted in-vitro in primary cultured human KCs. RESULTS: We found the expression of IARS was higher in psoriatic skin than in healthy controls. In IMQ-induced psoriasis-like C57BL/6 J mouse model, MUP reversed IMQ-induced keratinocytes proliferation, expression of inflammatory cytokines and infiltration of immune cells. Furthermore, in cultured human keratinocytes, MUP inhibited proliferation, but promoted apoptosis, which may be related with STAT3 signaling pathway. CONCLUSION: Our finding of blocking the infiltration of immune cells by inhibiting the formation of IARS, could be one mechanism to explain the effect of MUP in the treatment of psoriasis. Developing strategies targeting suppression IARS should open new perspectives for the treatment of psoriasis. Video Abstract.

Sprouty1 exerts a preventive effect on the initiation of psoriasis by inhibiting innate immune antimicrobial peptide cathelicidin and immunocytes.

OBJECTIVES: Psoriasis is an immune-mediated skin disease dominated by the cutaneous immune system. Keratinocytes have been considered important triggers that initiate psoriasis. The key molecules and events of keratinocytes that link the innate immune system in psoriasis must be investigated in more detail. Human psoriasis skin and primary human keratinocyte were detected in vitro. Epidermis specific transgenic mouse strain (Krt14-Sprouty1 tg) was used to further investigate psoriasis-like skin inflammation in vivo. MATERIALS AND METHODS: Bulk RNA sequencing of primary human keratinocyte screened differentially expressed genes, which was confirmed by quantitative real time PCR and Western Blot (WB). Moreover, we concomitantly reviewed open-accessed published RNAseq datasets of human psoriatic skin from GEO database. Immunohistochemical staining and immunofluorescence were used to detect Sprouty1 (SPRY1) expression in human psoriatic skin with and without anti-psoriasis treatments. Krt14-Sprouty1 tg was used to further investigate psoriasis-like skin inflammation, and followed by Hematoxylin and Eosin (HE) Staining, enzyme linked immunosorbent assay (ELISA), Western Blot and flow cytometry. RESULTS: Our data showed that Sprouty1 was decreased in psoriatic skin and keratinocytes. In imiquimod-induced psoriasis-like skin inflammation, the production of cathelicidin (camp/LL37) was inhibited by suppressing signal transducer and activator of transcription3 (Stat3) activation when Sprouty1 overexpressed in mouse epidermal keratinocytes. Moreover, CD11b+CCR2+ dendritic cells, IL-17A+ γδT cells, and Ly6C+ CD11c+ monocyte-derived dendritic cells were decreased in Krt14-Sprouty1 tg (STG) imiquimod-induced cutaneous inflammation. CONCLUSIONS: These findings indicate that Sprouty1 expressed in keratinocytes has a suppressive role in imiquimod-induced skin inflammation mediated by inhibiting the production of cathelicidin. Collectively, Sprouty1 plays a preventive role in psoriatic skin. Our data provide new evidence for the pathogenesis of psoriatic keratinocytes, and the link cutaneous innate immunity, that indicated Sprouty1 is a potential novel therapeutic target.

Cutaneous nerve fibers participate in the progression of psoriasis by linking epidermal keratinocytes and immunocytes.

Recent studies have illustrated that psoriatic lesions are innervated by dense sensory nerve fibers. Psoriatic plaques appeared to improve after central or peripheral nerve injury. Therefore, the nervous system may play a vital role in psoriasis. We aimed to clarify the expression of nerve fibers in psoriasis and their relationship with immune cells and keratinocytes, and to explore the effect of skin nerve impairment. Our results illustrated that nerve fibers in psoriatic lesions increased and were closely innervated around immune cells and keratinocytes. RNA-seq analysis showed that peripheral sensory nerve-related genes were disrupted in psoriasis. In spinal cord hemi-section mice, sensory impairment improved psoriasiform dermatitis and inhibited the abnormal proliferation of keratinocytes. Botulinum toxin A alleviated psoriasiform dermatitis by inhibiting the secretion of calcitonin gene-related peptide. Collectively, cutaneous nerve fibers participate in the progression of psoriasis by linking epidermal keratinocytes and immunocytes. Neurological intervention may be a new treatment strategy for psoriasis.

OAS1, OAS2, and OAS3 Contribute to Epidermal Keratinocyte Proliferation by Regulating Cell Cycle and Augmenting IFN-1‒Induced Jak1‒Signal Transducer and Activator of Transcription 1 Phosphorylation in Psoriasis.

Psoriasis is a systemic immune‒mediated inflammatory disease characterized by hyperproliferation and abnormal differentiation of epidermal keratinocytes. Recent studies have identified IL-17 and IL-23 as key drivers of psoriasis pathogenesis, but the underlying molecular mechanisms remain unclear. The 2'-5'-oligoadenylate synthetases (OASs), namely, OAS1, OAS2, OAS3, and OASL, are a family of IFN-induced enzymes with multiple antiviral activities, but their role in psoriasis is unknown. In this study, we identified the overexpression of OAS1, OAS2, and OAS3 in human lesional psoriatic skin and serum and found that their expression was downregulated by biologics. Moreover, OASs were highly expressed in epidermal keratinocytes, epidermal dendritic cells, epidermal CD3+ T cells, dermal antigen-presenting cells, and dermal T cells from the psoriatic epidermis and dermis, as determined by flow cytometry. In addition, OASs were upregulated by poly(I:C), poly(dA:dT), and IFN-1s but downregulated by Jak inhibitors in normal human epidermal keratinocytes. Furthermore, silencing of OASs inhibited the phosphorylation of Jak1 and signal transducer and activator of transcription 1. Knockdown of OASs suppressed keratinocyte proliferation by inhibiting cell cycle progression. Thus, OASs may be therapeutic biomarkers in psoriasis.

Quantitative Proteomic Profile of Psoriatic Epidermis Identifies OAS2 as a Novel Biomarker for Disease Activity.

Psoriasis is a common chronic inflammatory systemic disease. Epidermal proteins are considered to be important in maintaining skin barrier function, innate immunity, and inflammation. To define more possible roles of the epidermis in the pathogenesis of psoriasis, quantified proteomic analysis was used to screen and analyze the differentially expressed epidermal proteins between 16 psoriasis patients and 15 healthy controls. Upregulated differential expression proteins (DEPs) include several significant functional protein clusters, including antimicrobial peptides (AMPs) and antiviral proteins (AVPs). The levels of 2-5-oligoadenylate synthase 2 (OAS2) in both epidermis and serum levels were significantly elevated in psoriasis and were also positively correlated with Psoriasis Area Severity Index (PASI) scores and Body Surface Area (BSA) scores. Moreover, OAS2 expression in psoriatic skin significantly decreased after IL-17R mono-antibody treatment. It has been clarified that inflamed keratinocytes were the main source of abnormally increased OAS2 in psoriasis skin by immunofluorescence and primary cell cultures. Keratinocyte-derived OAS2 can be induced by not only IFNß, but also psoriasis associated cytokines like IL-17A and IL-6. This study revealed that AMPs and AVPs are two important functional protein clusters altering innate immune in psoriatic epidermis. OAS2 is a novel potential sensitive biomarker, which could predict the severity and activity of psoriasis, and could also be used as an indicator to evaluate or monitor the efficacy of clinical treatment.

Increased CCL24 and CXCL7 levels in the cerebrospinal fluid of patients with neurosyphilis.

BACKGROUND: Monocytes are recruited into the cerebrospinal fluid (CSF) of patients with neurosyphilis, suggesting abnormal chemokine expression. We aimed to investigate the aberrant expression of chemokines in the CSF of these patients. METHODS: CSF and serum samples were collected from patients with neurosyphilis between July 2017 and June 2019 in the Dermatology Department, Second Affiliated Hospital of Zhejiang University. Differences in the expression of 38 chemokines between patients with and without neurosyphilis were detected using RayBio® Human Chemokine Antibody Array C1. CCL24 and CXCL7 levels in the patients' CSF and serum were further measured using RayBio® CCL24 and CXCL7 ELISA kits. RESULTS: Ninety-three CSF and serum samples of patients with syphilis were collected. Antibody array analysis showed that the CSF levels of CCL24 (P = .0185), CXCL7 (P < .0001), CXCL13 (P < .0001), CXCL10 (P < .0001), and CXCL8 (P < .0001) were significantly higher in patients with than without neurosyphilis. ELISA confirmed significantly higher CCL24 and CXCL7 levels in the CSF of patients with than without neurosyphilis (CCL24: 6.082 ± 1.137 pg/mL vs 1.773 ± 0.4565 pg/mL, P = .0037; CXCL7: 664.3 ± 73.19 pg/mL vs 431.1 ± 90.54 pg/mL, P = .0118). Increased CCL24 and CXCL7 expression was seen throughout all neurosyphilis stages, had moderate diagnostic efficiency for neurosyphilis, and correlated poorly with CSF cell count and Venereal Disease Research Laboratory titer. CSF CCL24 levels also correlated poorly with CSF protein concentration. CONCLUSION: Abnormally high CSF chemokines levels may play a role in the pathogenesis of neurosyphilis.

Exosomal microRNA profiles from serum and cerebrospinal fluid in neurosyphilis.

OBJECTIVE: Changes in microRNAs (miRNAs) in the cerebrospinal fluid (CSF) are associated with different neurological diseases. Since alternations of miRNAs in neurosyphilis are insufficiently investigated, we analysed miRNAs in the CSF of patients suffering from neurosyphilis. METHODS: Exosomes were isolated from serum and CSF. Levels of 44 miRNAs were determined using quantitative real-time PCR-based miRNA array. RESULTS: In patients with neurosyphilis (NSP), miR-590-5p, miR-570-3p and miR-570-5p were upregulated in the CSF and serum, when compared with patients with syphilis without neurosyphilis (SP). miR-590-5p and miR-570-3p were significantly upregulated (p<0.001). The expression of miR-21-5p was upregulated only in the CSF of NSP. Significant downregulation was observed for miR-93-3p in the CSF and serum of NSP. No statistical difference was found in the expression of miR-7-5p, miR-1307-5p, miR-203a-3p, miR-16, miR-23b-3p and miR-27b-5p in the CSF and serum of NSP and SP. CONCLUSION: For the first time, regulation profiles in miRNA in the CSF and serum were analysed in NSP. We found significant differences in upregulation and downregulation. Therefore, miRNAs may be potential biomarkers for the presence of neurosyphilis.

[Leiomyoma of tongue: a case report].

Oral leiomyoma is a benign smooth muscle tumor. Leiomyoma occurs most frequently in the uterine myometrium, gastrointestinal tract, and skin. Occurrence in the oral cavity is considered rare, probably because of the paucity of smooth muscle tissue at this area. Smooth muscle tumors can occur at any age and usually appear as a slow growing, firm submucosal nodule. Most lesions are asymptomatic, although occasional tumors can be painful. The most common sites are lips, palate and tongue. The diagnosis of leiomyoma in the oral cavity is mainly determined by histological studies. The purpose of this article is to present a case of a 48 year-old woman with a leiomyoma of tongue.

[Effects of genistein on the expressions of cell apoptosis-related proteins in salivary adenoid cystic carcinoma cell line SACC-83].

PURPOSE: To investigate the molecular mechanism of cell apoptosis induced by tyrosine protein kinase inhibitor, genistein, in human salivary adenoid cystic carcinoma cell line SACC-83. METHODS: SACC-83 cells cultured in vitro were treated with genistein, the expressions of bax, bcl-2 and survivin proteins were detected with Western blotting, and the results were quantitatively analyzed by FluorChem V2.0 software, statistical analysis was performed with analysis of variance using SPSS11.5 software package. RESULTS: With the increase of concentration of genistein and the elongation of time, the expression of bax protein was significantly increased, but the expression of bcl-2 and survivin proteins was significantly decreased. Treated with 220 micromol/L genistein for 3 days, the expression level of bax protein was 3.43 folds of the control group (P<0.01),but the expression level of bcl-2 and survivin proteins was respectively 85%(P<0.05) and 35%(P<0.01) of the control group. CONCLUSION: The cell apoptosis induced by genistein in human salivary adenoid cystic carcinoma cell line SACC-83 may be associated with the upregulation of bax protein expression,and the downregulations of bcl-2 and survivin proteins expression.

[Effect of static magnetic field on bone morphogenetic protein 2 and collagen type I of osteoblast cell].

PURPOSE: To study the effect of static magnetic field on osteoblast,and to explore the possibility of osteogenesis of static magnetic field. METHODS: Rat calvarial osteoblasts were seeded on the 96-well culture plate, and exposed to 0.062T magnetic intensity field for 24 hours, 48 hours and 72 hours, respectively. Changes of BMP-2 and collagen type I in osteoblast were examined by Western blot. Immunohistochemical staining was carried out at different time periods. The data obtained were analyzed for ANOVA using SPSS 11.5 software package. RESULTS: The results of Western blot showed that magnetic static field affected expression of BMP-2 and collagen type I in osteoblast. The expression of BMP-2 in 48-hour group increased 2.1 fold and the expression of collagen type I in 72-hour group increased 1.6 fold compared to the control group (P<0.01). Moreover, the staining color of the collagen type I in cell of magnetic treated group was deeper than that of the control. CONCLUSIONS: Static magnetic field induced the expression of BMP-2 and stimulated secretion of collagen type I. The results indicate that osteoblasts are sensitive to 0.062T static magnetic field stimulation.

[Effects of Genistein on the proliferation and expression of survivin in salivary adenoid cystic carcinoma cell line SACC-83].

OBJECTIVE: To investigate the anti-proliferation effect of tyrosine protein kinase inhibitor, Genistein, on human salivary adenoid cystic carcinoma cell line SACC-83, and its effect on Survivin expression. METHODS: SACC-83 cells were treated with different concentration Genistein for different time, cell survival rate was calculated with MTT assay, apoptosis was detected with flow cytometry, the expression of Survivin was quantitatively analyzed by Western blotting and FluorChem V2.0 software. RESULTS: When treated with Genistein of certain concentration for certain time, SACC-83 cell growth was significantly inhibited. With the increase of concentration and elongation of acting time, the inhibitory effects increase. Treated with 220 micromol/L Genistein for 72 hours, SACC-83 cell growth was significantly inhibited, cell apoptosis was induced (P < 0.01), and the expression of Survivin decreased. CONCLUSION: Genistein inhibits the growth of human salivary adenoid cystic carcinoma cell line SACC-83, and induces cell apoptosis; the decrease of Survivin expression may be one of the mechanisms of Genistein inducing apoptosis.

Induction of dendritic cell maturation by pertussis toxin and its B subunit differentially initiate Toll-like receptor 4-dependent signal transduction pathways.

OBJECTIVE: Pertussis toxin (PT) has the capacity to activate dendritic cells (DCs) for the augmentation of cell-mediated immune responses. To investigate the mechanism(s) by which PT activates DCs, we investigated the effects of PT and its B-oligomer (PTB) on the maturation of human and mouse DCs and determined whether PT could act as a pathogen-associated molecular pattern to activate one of the Toll-like receptors (TLRs). METHODS: The effects of PT and PTB on the maturation of human and mouse DCs were analyzed in terms of surface marker expression, cytokine production, antigen-presenting capacity, and intracellular signaling. The participation of TLR4 in PT-induced signaling was determined by comparing the effect of PT on DCs derived from TLR4-deficient and wild-type mice, as well as by measuring PT-induced NF-kappaB activation in HEK293 cells transiently transfected to express various TLRs. RESULTS: Although both promoted phenotypic and functional maturation DCs, however, unlike PT that induced DC production of interleukin (IL)-6, tumor necrosis factor-alpha, IL-12, and interferon-inducible protein, PTB was capable of stimulating the production of interferon-inducible protein. Bone marrow-derived DCs from C3H/HeJ mice with defective TLR-4 alleles were unresponsive to PT and PTB, whereas DCs from C3H/HeN mice responded. In addition, PT induced NF-kappaB activation and IL-8 production in HEK293 cells transfected with a combination of TLR4 and MD2 but not in nontransfected or TLR2-transfected HEK293 cells. Comparison of the patterns of cytokine induction and intracellular signaling events in DCs treated by PT and PTB revealed that although PT, like lipopolysaccharide, triggered both MyD88-dependent and -independent pathways, PTB preferentially triggered MyD88-independent pathways. Interestingly, mouse splenocyte proliferation in response to PT and PTB was only partially dependent on TLR4. CONCLUSION: The data identify PT as another pathogen-associated molecular pattern that induces DC maturation in a TLR4-dependent manner. Unlike PT, which triggers both MyD88-dependent and -independent pathways, PTB only triggers the MyD88-independent pathway in DCs.