Rituximab in the Management of Autoimmune Bullous Diseases: A Treatment-Resistant Case Series from a Single Central European Referral Center.

Background and Objectives: Rituximab (RTX) has been the predominant treatment for autoimmune bullous diseases (AIBDs). The objective of this research was to assess the advantages and safety characteristics of RTX treatment in individuals with AIBD. This assessment focused on clinical remission and a reduction in glucocorticosteroid usage, its effect on the titers of autoantibodies targeting desmoglein-1 (DSG-1) and desmoglein-3 (DSG-3), and adverse occurrences during a 12-month follow-up period in a dermatology department within a Central European university context. Materials and Methods: Our case series involved eleven patients, including eight patients with pemphigus vulgaris, two with pemphigus foliaceus, and one with epidermolysis bullosa acquisita. They received a 1 g dose of rituximab, repeated over a two-week interval. Results: The reduction in a prednisone-equivalent dosage after 2, 6, and 12 months following the second RTX infusion was 65.05%, 73.99%, and 76.93%, in that order. The titers of antibodies against DSG-1 exhibited reductions of 43.29%, 75.86%, and 54.02% at 2, 6, and 12 months, respectively. By contrast, the antibody concentrations targeting DSG-3 displayed a decrease of 27.88%, 14.48%, and 5.09% at the corresponding time points. Over the course of the 12-month monitoring period, 18.18% of patients experienced disease relapse, while the remaining individuals achieved either complete or partial remission with minimal or no therapy. Adverse effects were noted in 36.36% of the patient population; they were mild, and no serious adverse effects were reported. Conclusions: RTX represents an efficacious and well-tolerated therapeutic option for the management of AIBD and merits consideration in cases of refractory AIBD. However, further research is imperative to delineate the most optimal dosage, dosing frequency, and total quantity of maintenance infusions required. Additionally, there is a compelling need for studies that explore the impact of RTX on individuals with AIBD who do not exhibit a significant reduction in anti-desmoglein autoantibody levels.

Intravenous Immunoglobulin for Autoimmune Bullous Diseases: A Case Series from a Central European Referral Center.

Background and Objectives: Autoimmune bullous diseases (AIBDs) may be treated with intravenous immunoglobulin (IVIG) infusions. This study aimed to evaluate the benefits and safety profiles of high-dose IVIG therapy in AIBD patients, as determined by clinical remission, the glucocorticosteroid-sparing effect, and adverse events at 12 months follow-up in a Central European university dermatology department setting. Materials and Methods: Our case series included 10 patients: five patients with pemphigus vulgaris, one with pemphigus herpetiformis, one with pemphigus foliaceus, one with bullous pemphigoid, two with epidermolysis bullosa acquisita. They underwent 4-12 monthly cycles of IVIG therapy at a dose of 2 g/kg per cycle. Results: The prednisone dosage reduction after 2, 6, and 12 months following the final IVIG course was 65.45%, 70.91%, and 76.37%, respectively. During the 12-month observation period, disease relapse was observed in 20% of patients, while others achieved complete or partial remission without or with minimal therapy. Side effects were seen in 80% of patients; they were transient and did not necessitate discontinuation of IVIG. Conclusions: IVIG demonstrates effectiveness as a treatment with a favorable safety profile. Nevertheless, its high cost remains a significant drawback, particularly in low-income countries. IVIG should be considered, especially in patients opposed to standard therapies or with contraindications to their use.

Treatment-naïve pemphigus patients showing IgG tissue deposits have serum IgG antibodies against desmoglein 1 detected more often than those against desmoglein 3: a monocentre laboratory experience.

Introduction: Pemphigus is a heterogeneous group of autoimmune acantholytic diseases. Aim: To check whether there is a relationship between detecting IgG deposits in the direct immunofluorescence (DIF) and finding IgG antibodies against particular desmoglein (DSG) isoforms in ELISA techniques in patients with pemphigus. Material and methods: Single-step DIF for revealing the deposits of IgA, IgM, IgG, IgG1, IgG4 and C3, and monoanalyte ELISAs or the multiplex ELISA were used for diagnosis. The Z test for two independent proportions was used for the statistical analysis. Results: We evaluated 19 consecutive treatment-naïve pemphigus patients, who exhibited IgG deposits, accompanied by other types of immunoreactants in various combinations, in DIF. Serum IgG antibodies against DSG1 were detected in 18 patients, whereas serum IgG antibodies against DSG3 were found in 10 patients. The statistical analysis showed that the proportion of anti-DSG1 antibody-positive individuals (18 of 19, 94.74%) was statistically significantly higher than the proportion of anti-DSG3 antibody-positive ones (10 of 19, 52.63%) (p = 0.0099). Conclusions: IgG deposition in the pemphigus pattern seems to be related to the presence of serum IgG antibodies against DSG1 rather than against DSG3. DSG1 may bind IgG more efficiently than DSG3 since DSG1 has a longer cytoplasmic region compared to that of DSG3.

Clinical significance of umbilical region involvement in pemphigus vulgaris in a series of 81 ethnic Poles: a comparative analysis of the distribution of lesions in two infrequent locations.

Introduction: Autoimmune bullous diseases are potentially life-threatening dermatoses which present with cutaneous and/or mucosal blisters, diagnosed on the basis of clinical manifestations, direct immunofluorescence of perilesional tissue, and serum testing for circulating autoantibodies. Sometimes, lesions in the navel can lead to the diagnosis of a bullous disease. Aim: To assess the frequency of occurrence of pemphigus lesions located in the navel area and nail apparatus in pemphigus vulgaris (PV) in ethnic Poles. Material and methods: Eighty one patients (31 males and 50 females, mean age 59 years) with dermatoses of the PV group diagnosed in 2002-2020 were retrospectively analysed using their photographic files. Statistical analysis was performed using the difference test between two proportions to check the difference between the percentage of PV patients with navel area involvement and nail apparatus involvement. Results: There was no statistically significant difference between PV patients with nail apparatus involvement (12.3%) and navel area involvement (14.8%) (p = 0.4632). Only females had lesions in the navel area in our series of PV patients. Conclusions: It is speculated that the causal relationship may exist between the female reproductive system and the pattern of expression of PV lesions around the umbilicus. The awareness that PV can infrequently affect the umbilical region and the nail apparatus should help in some cases to establish the diagnosis of PV. The periumbilical involvement can facilitate the performance of DIF in individuals with lesions in less accessible areas.

Conceptualization and validation of an innovative direct immunofluorescence technique utilizing fluorescein conjugate against IgG + IgG4 for routinely diagnosing autoimmune bullous dermatoses.

INTRODUCTION: Autoimmune bullous diseases (ABDs) are potentially life-threatening mucocutaneous illnesses that require diagnosis with direct immunofluorescence (DIF). In this study we compared the diagnostic accuracy of traditional DIF (DIFt; separate immunoglobulin (Ig) G, IgG1, IgG4, IgA, IgM and C3 deposits detection) and modified DIF (DIFm; simultaneous IgG + IgG4 deposits detection instead of separate IgG and IgG4 deposits detection) in routine diagnostics of ABDs. MATERIAL AND METHODS: Eighteen patients with ABDs (7 with pemphigus dermatoses and 11 with subepithelial ABDs) were evaluated with DIFt and DIFm. RESULTS: The agreement of detectability of IgG immunoreactants was obtained in 16 ABD cases (88.89%), as positive results in both DIFt and DIFm were obtained in 13 cases and negative results in both DIFt and DIFm were obtained in 3 cases. One ABD case (Brunsting-Perry pemphigoid) (5.56%) was negative in DIFm with a positive DIFt result (IgG1 deposits). One ABD case (bullous pemphigoid) (5.56%) had only C3 deposits in DIFt with a positive DIFm reading (IgG + IgG4 deposits). A statistically significant relationship (p = 0.0186) between DIFm and DIFt results was revealed using Fisher's exact test. CONCLUSIONS: Both DIFt and DIFm are useful methods to detect deposition of IgG immunoreactants, but it seems that the innovative DIFm method slightly increases the detectability of IgG/IgG4 immunoreactants in relation to DIFt. The introduction of DIFm into routine laboratory diagnostics of ABDs seems to be justified, as it enables the abandonment of separate FITC conjugates for IgG and IgG4, which is important for cost-effectiveness.

A comparative analysis of tuberculosis in vitro screening in pemphigus patients selected for treatment with rituximab.

INTRODUCTION: Patients qualified for the Polish government programme of treating severe pemphigus diseases with rituximab (RTX) available in 2018-2019 had to meet numerous criteria, including no active infectious disease. AIM: The clinical usefulness of tuberculosis screening with the QuantiFERON-TB Gold Plus (QFT-Plus) in native pemphigus patients selected for RTX treatment was statistically evaluated. MATERIAL AND METHODS: Eighteen pemphigus patients were examined with QFT-Plus prior to the intended RTX therapy. Ninety hospital employees examined with QFT-Plus due to contact with a cleaning worker who was diagnosed with active pulmonary tuberculosis were the control group. RESULTS: Six of 18 pemphigus patients had a positive QFT-Plus test result, one indefinite result and one initially indefinite and then negative. In the control group, 26 of 90 employees had a positive test result and none had an indefinite result. Statistical analysis by Fisher's exact test showed no statistically significant difference in QFT-Plus positive results between the groups (p = 0.5577). Only in 1 patient with recurrent mucocutaneous pemphigus vulgaris previously treated with traditional immunosuppression, lung changes were detected by computed tomography. No employee had any changes in the chest radiograph. CONCLUSIONS: Prior immunosuppression and autoimmunity might be the cause of indefinite test results, but they do not seem to increase positive results. In the native population, the QFT-Plus screening reveals a significant population exposure to M. tuberculosis infection independent of pemphigus autoimmunity, and such screening can be a starting point for identifying patients requiring anti-tuberculosis drug prophylaxis before combined RTX-glucocorticosteroid treatment.

High-frequency ultrasonography a new quantitative method in evaluation of skin lymphomas-First comparative study in relation to histopathology.

INTRODUCTION: High-frequency ultrasonography (HF-USG) is a noninvasive method used in evaluation of depth and width of skin neoplasms. Recent data suggest that this method may also supplement objective clinical assessment in skin lymphomas, especially in mycosis fungoides, where subepidermal low echogenic band (SLEB) can be observed. The aim of the study was to present characteristic ultrasonic picture of MF in relation to histopathologic findings. MATERIALS AND METHODS: Ten patients diagnosed as MF were included in the study. The USG examination was performed with the use of 20 MHz transducer within representative plaque. From the scanning lesion, the skin biopsy was taken. The relationship between histopathologic infiltrate with clonal T cells and USG image was investigated. RESULTS: In all analyzed sonograms obtained from lesional skin of early-stage MF, we could detect the presence of subepidermal low echogenic band (SLEB). We detected strong correlations between SLEB thickness and the thickness of subepidermal infiltration (0.994, P < 0.05). CONCLUSIONS: Subepidermal low echogenic band is a typical sign of infiltrative stage of MF, and its thickness may depend on the type of skin lesion. HF-USG may be a reliable noninvasive method of quantitive assessments in MF, which corresponds to the thickness on T-cell infiltration in histopathology.

An update on direct immunofluorescence for diagnosing dermatitis herpetiformis.

This mini-review presents an update on the direct immunofluorescence (DIF) for diagnosing dermatitis herpetiformis. The DIF of uninvolved, perilesional skin is a crucial laboratory procedure in diagnosing dermatitis herpetiformis (DH). IgA deposits at the dermal-epidermal junction (DEJ) of perilesional skin with DIF can also be found in coeliac patients with inflammatory skin diseases different from DH. In certain patients presenting with the rash resembling DH, the deposition of exclusively C3 at DEJ can be found. The term "granular C3 dermatosis" was proposed to name such a rash. Recent data on DH suggest that perhaps the very concept of DH that we are universally accepting now is misleading and should be revised.

Clinical evaluation of a multiparametric ELISA as a rapid tool for routinely diagnosing IgG-mediated autoimmune blistering dermatoses in ethnic Slavs.

BACKGROUND: Technical innovation of autoimmune blistering dermatoses (ABDs) diagnosis aimed at multiplex approach. Two multiparametric ELISA tests are commercially available for ABDs serology. The aim was to compare diagnostic accuracy of multiparametric and monospecific ELISAs and to examine the diagnostic value/agreement of multivariant ELISA in compliance with traditional diagnostic setup for ABDs. METHODS: In total, 128 sera from suspected ABDs patients were studied (27 sera in order to compare ELISAs). Multivariant ELISA (detection of IgG against desmoglein 1 and 3 - DSG1/3; BP180, BP230, envoplakin, type VII collagen), monovariant ELISA, and statistical analysis were performed. RESULTS: With the use of sera from patients with suspected ABDs, the multiparametric ELISA yield an agreement of 84% with traditional stepwise diagnostics. Multivariant ELISA with BP180 and BP230 showed 87.5% and 80% sensitivity, 87.5% and 91% specificity, 87.5% reliability as well as 87.5% and 80% positive predictive value, 87.5% and 91% negative predictive value, respectively, in relation to monospecific ELISA. Multivariant ELISA with DSG1 and DSG3 showed 50% and 80% sensitivity, 100% and 80% specificity, 85% and 80% reliability as well as 100% and 57% positive predictive value, 82% and 92% negative predictive value, respectively, in relation to monospecific ELISA. A better rate of agreement was observed among ELISA systems with BP180 and BP230, than with ELISA systems with DSG1 and DSG3. CONCLUSION: Multivariant ELISA test combined with clinical examinations and DIF is recommended as a minimal approach to diagnosing ABDs in ethnic Slavs.

Cyclooxygenase-2 expression in actinic keratosis.

INTRODUCTION: Actinic keratosis (AK) is a common age-associated dermatosis typical for skin with photo-ageing features. Actinic keratosis lesions transform into invasive squamous cell carcinoma, if left untreated, but inductive factors remain unknown. A role of prostaglandins in the neoplastic process has been postulated. AIM: To evaluate the possible correlation between cyclooxygenase-2 (COX-2) antigen expression in the immunohistochemical reaction and the stage of AK using the keratinocytic intraepidermal neoplasia (KIN) classification, age, sex and skin phenotype. MATERIAL AND METHODS: Skin samples of AK were examined histopathologically using the KIN classification. Immunohistochemical analysis of COX-2 expression was conducted using a commercially available kit and Image Processing and Analysis in Java. The intensity was presented as the percentage of cells with a positive reaction. RESULTS: Out of the 94 subjects with AK (aged 51-93 years; mean: 76.51 ±9.64), 58 were female and 36 male. Phenotype 2 was found in 50 and phenotype 3 in 44 patients. Mean values of positive immunohistochemical reaction for COX-2 were 2.16 ±6.56% for women and 1.96 ±6.59% for men (2.47 ±6.61%), with no statistically significant difference. Mean values of anti-COX-2 antibody reaction were 2.30 ±6.82% in the KIN1 group and 2.48 ±7.01% in the KIN2 group, while no expression was found in all cases with KIN3. No statistically significant differences were found between the percentage of COX-2 positive cells in KIN1/KIN2. CONCLUSIONS: No statistically significant correlations between the intensity of COX-2 reaction and AK stage were found. Cyclooxygenase-2 expression in AK is not affected by age, sex, or skin phenotype.

Cowpox virus infection in a child after contact with a domestic cat: a case report.

Human cowpox represents a seldom diagnosed zoonosis but this diagnosis should be considered more frequently as the number of cases has increased in recent years. We describe a case of cowpox in an 11-yearold boy following regular direct daily contact with a domestic cat. The 11-year-old patient, an otherwise healthy boy, demonstrated skin ulceration located at his chin, with enlargement of regional lymph nodes and fever reaching 39°C. The diagnosis of cowpox was made on the basis of PCR involving DNA isolated from a scab covering the skin lesion. Application of PCR involving DNA isolated from the scab covering the lesion with parallel use of OPXV-specific (ORF F4L) and CPXV-specific (ORF B9R) oligonucleotide primer sequences is recommended for rapid laboratory confirmation of the diagnosis.

A comparative study of expression of Fc receptors in relation to the autoantibody-mediated immune response and neutrophil elastase expression in autoimmune blistering dermatoses.

Here we investigated the cutaneous CD32A and CD89 expression in relation to the neutrophil elastase (NE) expression and serum level of anti-desmoglein 1 and 3 (DSG1/DSG3) IgG in pemphigus, anti-BP180/BP230 IgG in bullous pemphigoid (BP), anti-gliadin nonapeptides (npG), tissue (tTG), and epidermal transglutaminases (eTG) IgA in dermatitis herpetiformis (DH). The examined material consisted of skin/mucosal tissues and sera. In total, 87 patients were studied. Immunohistochemistry on paraffin-embedded sections with quantitative digital morphometry was used to measure the intensity of CD32A/CD89/NE expressions. Levels of anti-DSG1/DSG3 IgG, anti-BP180/BP230 IgG, and anti-npG/tTG/eTG IgA were evaluated with ELISAs. CD32A was abundantly expressed in cutaneous lesions in pemphigus and BP. We found no statistically significant correlation between the CD32A/CD89 and NE expression intensities in pemphigus, BP, and DH. There was a significant correlation between CD89 expression and anti-npG IgA in DH. Our results revealed a lack of correlation between CD32A expressions and anti-DSG1/DSG3 IgG levels in pemphigus, anti-BP180/BP230 IgG in BP as well as CD89 expression and anti-tTG/eTG IgA in DH. CD89 seems to be linked with gluten intolerance in DH rather than with proteolytic destruction of dermal-epidermal junction. CD32A appears to play an important role in mediating skin injury in pemphigus and BP, but probably independently from specific autoantibodies.

Analysis of the autoimmune response against BP180 and BP230 in ethnic Poles with neurodegenerative disorders and bullous pemphigoid.

Recent studies postulated the association between bullous pemphigoid (BP) and neurodegenerative disorders (ND). The autoantibodies to BP180 and/or BP230 may be present not only in BP, but also in ND as neuronal isoforms of these proteins are identified in the central nervous system. However, there are only scant data about the precise pathogenetic mechanisms interlinking ND and BP as well as the immunologic profile in these patients. The aim is to analyze the serological immunopathological profiles (anti-BP180 IgG, anti-BP230 IgG) in BP patients with and without ND in order to identify the specific autoantibody(ies) and corresponding antigens responsible for ND development in BP patients. Altogether, 82 ethnic Poles with BP and their medical records were examined (62 BP-ND; 20 BP+ND). Levels of serum anti-BP180/BP230 IgG in BP patients were evaluated with ELISAs. The statistical analyses involved Pearson chi-squared test, Mann-Whitney U-test and ranking of autoantibodies. The prevalence of ND among BP patients was 24.4%. There were no statistically significant differences in autoantigens profiles (anti-BP180/anti-BP230 IgG) between BP+ND and BP-ND groups. There was no relationship between ND development and anti-BP180/anti-BP230 IgG level (p = 0.5933, p = 0.4701, respectively). The autoantibodies levels of BP+ND and BP-ND patients show insignificant differences suggesting that also in ethnic Poles a hypothetical pathogenetic association of BP and ND, but not only an aging-related epidemiological one, appears to be independent of a particular BP antigen. Nevertheless, it cannot be excluded that phenomena of epitopes spreading, immune cross-reaction and conformational changes in BP180/BP230 may underlie BP development in ND patients.

Dew drops on spider web appearance: a newly named pattern of IgG4 deposition in pemphigus with direct immunofluorescence.

Novel appearances in cutaneous pathology as well as mucocutaneous clinical signs are being described which indicate that this is still an attractive area for exploration. The H + E histology terms of "decorated tomb stoning" and "undecorated tomb stoning", advocated by some pathologists, are misleading and as such should be avoided. Here, an appearance of IgG4 pemphigus deposits examined cost-effectively with direct immunofluorescence and suggested to be called "dew drops on spider web" is depicted in depth.

Reviewing putative industrial triggering in pemphigus: cluster of pemphigus in the area near the wastewater treatment plant.

A range of pemphigus is relatively rare potentially fatal group of autoimmune blistering dermatoses. Usually, there is no apparent triggering, while in some predisposed patients there are alleged environmental/industrial inducing factors. In a short time period (4 years), we diagnosed 3 novel cases of pemphigus (1 pemphigus vulgaris, 1 pemphigus foliaceus and 1 shift from pemphigus foliaceus into pemphigus vulgaris) at a clinical and laboratory level (ELISA, immunofluorescence studies). We discuss a possible common inducing mechanism as these patients inhabit one estate of the Poznan suburbia (Kozieglowy, population < 12,000), Greater Poland district, Poland, and review literature data on alleged pemphigus triggers. To the best of our knowledge, this is the first report exploring the putative association between pemphigus diseases and wastewater treatment plant waterborne or volatile by-products in the vicinity of such a facility.

Accuracy of molecular diagnostics in pemphigus and bullous pemphigoid: comparison of commercial and modified mosaic indirect immunofluorescence tests as well as enzyme-linked immunosorbent assays.

INTRODUCTION: Pemphigus and bullous pemphigoid (BP) are identified by autoantibodies (abs) against desmoglein 1, 3 (DSG1/3) and BP180/BP230, respectively. A novel mosaic to indirect immunofluorescence (IIF) using purified BP180 recombinant proteins spotted on slide and transfected cells expressing BP230, DSG1, DSG3 is available. The commercial (IgG detection) and modified (IgG4 detection) mosaic for indirect immunofluorescence (IIFc - IIF commercial, IIFm - IIF modified) and IgG ELISAs were evaluated in pemphigus and bullous pemphigoid (BP) molecular diagnostics. AIM: To compare diagnostic accuracy of commercial (IgG detection) and modified (IgG4 detection) mosaic IIF assay and to examine the diagnostic value of ELISAs in relation to mosaic IIF in routine laboratory diagnostics of pemphigus and BP. MATERIAL AND METHODS: Sera from 37 BP and 19 pemphigus patients were studied. Associations between tests were assessed using Fisher's exact test. RESULTS: There are associations between the positive/negative samples detected by IIFc with desmoglein1 (DSG1)/desmoglein3 (DSG3)/BP230 transfected cells and ELISAs and no association between anti-BP180 IgG detection by IIFc and ELISA. IIFm with DSG1 and DSG3 showed both 100% sensitivity and 100% and 78% specificity, respectively, and 100% and 83% positive predictive value in relation to IIFc. IIFm with BP230 had 87% specificity, 55% sensitivity, whereas IIFm with BP180 had a 100% sensitivity and 13% specificity in relation to IIFc. CONCLUSIONS: The IIFc with DSG1/DSG3/BP230 transfected cells, excluding BP180 spots, is an alternative method to ELISA in pemphigus/BP diagnostics. IgG4 antibodies, both pathogenically and diagnostically important, are inconsistently detectable with IIFm.

Neurodegenerative disorders, bullous pemphigoid and psoriasis: a comparative study in ethnic Poles indicates that Parkinson's disease is more relevant to bullous pemphigoid.

INTRODUCTION: Bullous pemphigoid (BP) is an autoimmune blistering dermatosis of the elderly with autoimmunity to hemidesmosomal proteins, BP180 and BP230, which are expressed also in neuronal tissue. AIM: The aim here was to retrospectively compare the prevalence of neurodegenerative disorders (ND), particularly Parkinson's disease (PD), unspecified conditions manifesting as dementia and stroke, in two groups of ethnic Poles, with BP and with psoriasis (Ps), in order to obtain data whether BP is more prone to coexist with ND than Ps in the elderly. Psoriasis was chosen in this comparative study as it was considered to be a paradigm of cutaneous disease with systemic manifestations. MATERIAL AND METHODS: The available medical records of 96 BP patients and 149 Ps patients over 70 years of age were analyzed for the presence of ND. RESULTS: There were no statistically significant differences in prevalence of ND without specifying the type and ND types analyzed between BP and Ps groups, except for a higher prevalence of PD in the BP group. CONCLUSIONS: Thus, regarding population aging and increasing incidence and prevalence of BP corresponding with that phenomenon in various ethnicities, it appears justified to expand studies of a possible immunopathogenic relationship, appearing to be PD-related, between BP and ND.

Bullous pemphigoid and neurodegenerative diseases: a study in a setting of a Central European university dermatology department.

Bullous pemphigoid (BP) is an autoimmune blistering dermatosis of the elderly mediated by IgG and IgE antibodies to skin hemidesmosomal proteins, BP180 and/or BP230, that occur physiologically also in neuronal tissue. It was reported that BP is associated with neurodegenerative diseases (ND). We performed a retrospective study in a setting of a Central European university dermatology department on prevalence of ND in 94 BP patients. 26 out of 94 BP patients had at least one ND. ND included: Parkinson's disease, dementia, stroke, hear loss, tinnitus, blindness, vertigo, neurosyphilis, systemic sclerosis, and epilepsy. Since population aging is conceivably responsible for the rising number of BP cases as a result of immunosenescence-related phenomena, the plausible BP-specific immunopathogenetic relationship between BP and ND deserves to be further experimentally explored.