Parsnp 2.0: scalable core-genome alignment for massive microbial datasets.

MOTIVATION: Since 2016, the number of microbial species with available reference genomes in NCBI has more than tripled. Multiple genome alignment, the process of identifying nucleotides across multiple genomes which share a common ancestor, is used as the input to numerous downstream comparative analysis methods. Parsnp is one of the few multiple genome alignment methods able to scale to the current era of genomic data; however, there has been no major release since its initial release in 2014. RESULTS: To address this gap, we developed Parsnp v2, which significantly improves on its original release. Parsnp v2 provides users with more control over executions of the program, allowing Parsnp to be better tailored for different use-cases. We introduce a partitioning option to Parsnp, which allows the input to be broken up into multiple parallel alignment processes which are then combined into a final alignment. The partitioning option can reduce memory usage by over 4× and reduce runtime by over 2×, all while maintaining a precise core-genome alignment. The partitioning workflow is also less susceptible to complications caused by assembly artifacts and minor variation, as alignment anchors only need to be conserved within their partition and not across the entire input set. We highlight the performance on datasets involving thousands of bacterial and viral genomes. AVAILABILITY AND IMPLEMENTATION: Parsnp v2 is available at https://github.com/marbl/parsnp.

Defining D-irAEs: consensus-based disease definitions for the diagnosis of dermatologic adverse events from immune checkpoint inhibitor therapy.

With an increasing number of patients eligible for immune checkpoint inhibitors, the incidence of immune-related adverse events (irAEs) is on the rise. Dermatologic immune-related adverse events (D-irAEs) are the most common and earliest to manifest, often with important downstream consequences for the patient. Current guidelines lack clarity in terms of diagnostic criteria for D-irAEs. The goal of this project is to better define D-irAE for the purposes of identification, diagnosis, and future study of this important group of diseases.The objectives of this project were to develop consensus guidance for an approach to D-irAEs including disease definitions and severity grading. Knowing that consensus among oncologists, dermatologists, and irAE subspecialists would be critical for usability, we formed a Dermatologic irAE Disease Definition Panel. The panel was composed of 34 experts, including oncologists, dermatologists, a rheumatologist, and an allergist/immunologist from 22 institutions across the USA and internationally. A modified Delphi consensus process was used, with two rounds of anonymous ratings by panelists and two virtual meetings to discuss areas of controversy. Panelists rated content for usability, appropriateness, and accuracy on 9-point scales in electronic surveys and provided free text comments. A working group aggregated survey responses and incorporated them into revised definitions. Consensus was based on numeric ratings using the RAND/UCLA Appropriateness Method with prespecified definitions.Following revisions based on panelist feedback, all items received consensus in the second round of ratings. Consensus definitions were achieved for 10 core D-irAE diagnoses: ICI-vitiligo, ICI-lichen planus, ICI-psoriasis, ICI-exanthem, ICI-bullous pemphigoid, ICI-Grover's, ICI-eczematous, ICI-eruptive atypical squamous proliferation, ICI-pruritus without rash, and ICI-erosive mucocutaneous. A standard evaluation for D-irAE was also found to reach consensus, with disease-specific exceptions detailed when necessary. Each disorder's description includes further details on disease subtypes, symptoms, supportive exam findings, and three levels of diagnostic certainty (definite, probable, and possible).These consensus-driven disease definitions standardize D-irAE classification in a useable framework for multiple disciplines and will be the foundation for future work. Given consensus on their accuracy and usability from a representative panel group, we anticipate that they can be used broadly across clinical and research settings.

Expert Recommendations on Use of Topical Therapeutics for Vitiligo in Pediatric, Adolescent, and Young Adult Patients.

Importance: Evidence-based recommendations for the treatment of vitiligo in pediatric, adolescent, and young adult patients in the US are needed. Objective: To develop evidence- and consensus-based expert recommendations on the diagnosis and treatment of vitiligo in young patients. Evidence Review: A process was developed to produce consensus recommendations addressing questions regarding pediatric vitiligo. A librarian-conducted literature review was performed using articles that met the inclusion criteria: published in English, containing primary data (including meta-analysis) and pediatric-specific data, and analysis of 6 or more patients. Included articles were graded by the Strength of Recommendation Taxonomy criteria and Oxford Centre for Evidence-based Medicine's Levels of Evidence and Grades of Recommendation. Research questions were reviewed on May 9, 2022, through a video conference. One month after the conference, participants participated in an online survey documenting their level of agreement with the generated statements, using a 5-point Likert scale. Findings: Articles on topical corticosteroids and/or topical calcineurin inhibitors (n = 50), topical Janus kinase inhibitors (n = 5), pseudocatalase (n = 2), and microdermabrasion (n = 2) met inclusion criteria. Forty-two recommendations were made on the diagnosis of vitiligo and optimal topical therapeutics, with 33 recommendations obtaining a 70% or greater composite agreement and strong agreement. Topical calcineurin inhibitors twice daily, topical corticosteroids with time limitation due to atrophy risk, and topical ruxolitinib, 1.5%, cream-used off-label for patients younger than 12 years and limited to nonsegmental vitiligo-were identified as evidence-based first-line therapies in the management of pediatric and adolescent patients, with specific guidance on age-based data, minimum therapeutic trial of 6 months or greater, prolonged therapy to prevent recurrence, and the positive benefit of coordinated use of UV therapeutic sources. Conclusions and Relevance: Evidence supports the use of topical calcineurin inhibitors, topical corticosteroids, and topical Janus kinase inhibitors as effective therapeutics for vitiligo in pediatric, adolescent, and young adult patients, with specific decisions on choice of agent based on factors such as site location, body surface area, and age.

Parsnp 2.0: Scalable Core-Genome Alignment for Massive Microbial Datasets.

Motivation: Since 2016, the number of microbial species with available reference genomes in NCBI has more than tripled. Multiple genome alignment, the process of identifying nucleotides across multiple genomes which share a common ancestor, is used as the input to numerous downstream comparative analysis methods. Parsnp is one of the few multiple genome alignment methods able to scale to the current era of genomic data; however, there has been no major release since its initial release in 2014. Results: To address this gap, we developed Parsnp v2, which significantly improves on its original release. Parsnp v2 provides users with more control over executions of the program, allowing Parsnp to be better tailored for different use-cases. We introduce a partitioning option to Parsnp, which allows the input to be broken up into multiple parallel alignment processes which are then combined into a final alignment. The partitioning option can reduce memory usage by over 4x and reduce runtime by over 2x, all while maintaining a precise core-genome alignment. The partitioning workflow is also less susceptible to complications caused by assembly artifacts and minor variation, as alignment anchors only need to be conserved within their partition and not across the entire input set. We highlight the performance on datasets involving thousands of bacterial and viral genomes. Availability: Parsnp is available at https://github.com/marbl/parsnp.

Zeeman Field-Induced Two-Dimensional Weyl Semimetal Phase in Cadmium Arsenide.

We report a topological phase transition in quantum-confined cadmium arsenide (Cd_{3}As_{2}) thin films under an in-plane Zeeman field when the Fermi level is tuned into the topological gap via an electric field. Symmetry considerations in this case predict the appearance of a two-dimensional Weyl semimetal (2D WSM), with a pair of Weyl nodes of opposite chirality at charge neutrality that are protected by space-time inversion (C_{2}T) symmetry. We show that the 2D WSM phase displays unique transport signatures, including saturated resistivities on the order of h/e^{2} that persist over a range of in-plane magnetic fields. Moreover, applying a small out-of-plane magnetic field, while keeping the in-plane field within the stability range of the 2D WSM phase, gives rise to a well-developed odd integer quantum Hall effect, characteristic of degenerate, massive Weyl fermions. A minimal four-band k·p model of Cd_{3}As_{2}, which incorporates first-principles effective g factors, qualitatively explains our findings.

Two-Dimensional Topological Insulator State in Cadmium Arsenide Thin Films.

Two-dimensional topological insulators (2D TIs) are a highly desired quantum phase but few materials have demonstrated clear signatures of a 2D TI state. It has been predicted that 2D TIs can be created from thin films of three-dimensional TIs by reducing the film thickness until the surface states hybridize. Here, we employ this technique to report the first observation of a 2D TI state in epitaxial thin films of cadmium arsenide, a prototype Dirac semimetal in bulk form. Using magnetotransport measurements with electrostatic gating, we observe a Landau level spectrum and quantum Hall effect that are in excellent agreement with those of an ideal 2D TI. Specifically, we observe a crossing of the zeroth Landau levels at a critical magnetic field. We show that the film thickness can be used to tune the critical magnetic field. Moreover, a larger change in film thickness causes a transition from a 2D TI to a 2D trivial insulator, just as predicted by theory. The high degree of tunability available in epitaxial cadmium arsenide heterostructures can thus be used to fine-tune the 2D TI, which is essential for future topological devices.

Hip effusions or iliopsoas hematomas on ultrasound in identifying hip fractures in the emergency department.

OBJECTIVE: We evaluated the sensitivity, specificity, predictive values, and likelihood ratios of hip effusion and/or iliopsoas hematoma on point-of-care ultrasound (POCUS) performed by ultrasound fellows and fellowship trained emergency providers to identify hip fractures in emergency department (ED) patients with a high suspicion of hip fracture. METHODS: This was a prospective observational study of a convenience sample of patients with high suspicion of hip fracture at two academic EDs between 2018 and 2021. Patients with negative x-rays who did not receive further imaging with magnetic resonance imaging (MRI) or computed tomography (CT) were excluded. Sonographers were blinded to clinical data and ED imaging results. At the primary site, 8 ultrasound fellows and 4 emergency ultrasound fellowship-trained emergency providers performed the ultrasonographic examinations. At the secondary site, 2 ultrasound fellows, 4 emergency ultrasound-fellowship trained physicians, and 1 sports medicine fellowship-trained emergency provider performed the ultrasonographic examinations. A positive ultrasound was defined as either the presence of a hip effusion or iliopsoas hematoma on the affected extremity. The primary outcome measures were sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) of POCUS findings for identification of a hip fracture compared with a ranked composite reference standard consisting of x-ray, CT, or magnetic resonance imaging (MRI); the highest-level test performed for each patient was used for comparison. RESULTS: Among 213 patients analyzed, all 213 received an x-ray, 116 received a CT scan, and 14 received an MRI; 113/213 x-rays (53.1%), 35/116 CT scans (30.2%), and 7/14 MRIs (50.0%) were positive for a hip fracture. A total of 123 patients were diagnosed with a hip fracture (57.7%). There were 13 false negative x-ray results. Overall, compared with the reference standard of x-ray, CT, or MRI, POCUS had a sensitivity of 97% (95% CI: 94%, 100%), specificity of 70% (95% CI: 61%, 79%), PPV of 82% (95% CI: 75%, 88%), and NPV of 94% (95% CI: 88%, 100%) in the identification of hip fractures; with a positive likelihood ratio of 3.22 (95% CI: 2.35, 4.43) and negative likelihood ratio of 0.05 (95% CI: 0.02, 0.12). CONCLUSION: In a convenience sample of ED patients with high clinical suspicion for hip fracture, the presence of a hip effusion and/or iliopsoas hematoma on POCUS performed by expert emergency ultrasonographers showed high sensitivity in diagnosing patients with a hip fracture.

Systematic Review of Systemic Corticosteroid Effects on Patch Testing.

ABSTRACT: Systemic corticosteroids are commonly used as a short-term management option for inflammatory skin conditions, such as contact dermatitis. The purpose of our systematic review was to compare presence and degree of patch test reactions with or without different doses of systemic corticosteroid therapy. The relationship between 20, 30, and 40 mg daily doses of prednisone and retained, diminished, and negated reactions was not linear, whereas the reaction ratings for all patches placed with or without corticosteroid therapy revealed trends toward lower intensity reactions while receiving prednisone ( P < 0.0001, χ 2 , for all doses of prednisone). Our review provides insight into directions for future studies that examine the effect of corticosteroids on patch testing.

Topical treatments for early-stage mycosis fungoides using Grading Recommendations Assessment, Development and Evaluation (GRADE) criteria: A systematic review.

BACKGROUND: Mycosis fungoides (MF) is a cutaneous lymphoma; most patients present with early, skin-limited disease and are managed by dermatologists. OBJECTIVE: The purpose of this study was to systematically review and assess the evidence on topical treatments for early-stage (IA, IB, IIA) MF. METHODS: We performed a literature search via MEDLINE, Embase, Web of Science, and Cochrane databases. Grading Recommendations Assessment, Development and Evaluation (GRADE) criteria were used to assess the certainty of the data. RESULTS: Two searches yielded 1252 references; 26 met the inclusion criteria and included literature on nitrogen mustard, retinoids, corticosteroids, carmustine, fluorouracil, methotrexate-laurocapram, hexadecylphosphocholine, peldesine, ingenol mebutate, topical methotrexate with oxygen flow-assisted LP3 carrier, and resiquimod. Most studies were single intervention, observational series. Nitrogen mustard, with the most published reports, was effective with 12%-82% early-stage MF patients (total n > 1000) achieving complete remission (CR) (low certainty evidence). Clinical CR was achieved among 10%-60% treated with topical retinoids (low certainty evidence). Two moderate-sized retrospective case series on topical steroids had 18%-63% CR (low certainty evidence). Only single studies were available for the other therapies. CONCLUSIONS: For most outcomes of interest, the GRADE certainty for topical therapies for early-stage MF was low. Further randomized controlled trials and inclusion of quality of life indicators are needed.

Local radiation and phototherapy are the most cost-effective treatments for stage IA mycosis fungoides: A comparative decision analysis model in the United States.

BACKGROUND: Treatments for early-stage mycosis fungoides (MF) include topical steroids, topical nitrogen mustard, topical bexarotene, narrowband ultraviolet B (NBUVB), psoralen plus ultraviolet A (PUVA), and local radiation. The relative cost-effectiveness of each treatment given the differences in treatment failure, disease progression, and therapy escalation is not established. OBJECTIVE: To compare the cost-effectiveness (CE) of treatment options for stage IA MF. METHODS: A state-transition model was constructed with health states of stage IA to stage IV disease, no MF, and death. Treatment-specific remission and relapse rates were obtained from the literature. Lifetime costs were calculated by accounting for medications, office visits, laboratory monitoring, related procedures, work absences, and travel. RESULTS: The order of CE of the study treatments was determined to be as follows: local radiation, $225,399 for 15.40 life-years (LYs); NBUVB, $344,728 for 15.17 LYs; PUVA, $371,741 for 15.07 LYs; topical corticosteroids, $469,354 for 14.65 LYs; topical nitrogen mustard, $951,662 for 14.29 LYs; and topical bexarotene, 11,892,496 for 13.55 LYs. Sensitivity analyses confirmed the CE rankings. LIMITATIONS: We assumed a constant probability of response, relapse rates, and 3-month treatment intervals. CONCLUSIONS: Local radiation is the most cost-effective treatment for limited local disease, whereas phototherapy (NBUVB or PUVA) is cost-effective for generalized disease. Our findings can serve to inform future studies and recommendations regarding selection of therapy for stage IA MF.

Reduced-Intensity Conditioning Regimens, Prior Chronic Lymphocytic Leukemia, and Graft-Versus-Host Disease Are Associated with Higher Rates of Skin Cancer after Allogeneic Hematopoietic Stem Cell Transplantation.

To assess incidence and risk factors for skin cancer associated with allogeneic hematopoietic stem cell transplantation, we evaluated 1,974 adult allogeneic hematopoietic stem cell transplantation patients from Beth Israel Deaconess Medical Center and Dana-Farber Cancer Institute who received transplants between January 1995 and July 2013 for hematologic malignancy and survived at least 100 days. Median age was 51.1 years, and median follow-up time was 3 years. Overall, 119 patients had 221 skin cancers. The incidences of squamous cell carcinomas (incidence rate ratio = 9.8; 95% confidence interval = 7.7-12.3), basal cell carcinomas (incidence rate ratio = 2.5; 95% confidence interval = 1.9-3.2), and melanoma (standardized incidence ratio = 3.3; 95% confidence interval = 1.7-5.9) were elevated in our cohort. In multivariable models, risk factors for squamous cell carcinomas were increased age (P < 0.0001), chronic lymphocytic leukemia (P = 0.02), and chronic graft-versus-host disease (P = 0.0002). Risk factors for basal cell carcinomas were chronic lymphocytic leukemia (P = 0.003), reduced-intensity conditioning (P = 0.02), acute graft-versus-host disease (P = 0.03), and chronic graft-versus-host disease (P = 0.003). To our knowledge, previously unreported risk factors in this contemporary cohort include prior CLL for squamous cell carcinoma and basal cell carcinoma and reduced-intensity conditioning for basal cell carcinoma. This study also supports chronic graft-versus-host disease as a risk factor for nonmelanoma skin cancer, particularly squamous cell carcinoma.

A primary role for human central memory cells in tissue immunosurveillance.

Central memory T cells (TCM) patrol lymph nodes, providing central immunosurveillance against known pathogens, but have not been described as conducting primary tissue immunosurveillance. We analyzed the expression of tissue-homing addressins in human TCM vs effector memory T cells (TEM) from the same donors. In humans, the majority of human TCM were tropic for either skin or gut, and the overall tissue tropism of TCM was comparable to that of TEM TCM were present in healthy, noninflamed human skin, lung, colon, and cervix, suggesting a role for TCM in the primary immunosurveillance of peripheral tissues. TCM also had potent effector functions; 80% of CD8+ TCM produced TC1/TC2/TC17/TC22 cytokines. TCM injected into human skin-grafted mice migrated into skin and induced inflammatory eruptions comparable to TEM-injected mice. In summary, human TCM express peripheral tissue-homing receptors at levels similar to their effector memory counterparts, are found in healthy human tissues, have impressive effector functions, and can act alone to induce skin inflammation in human engrafted mice. Our studies support a novel role for human TCM in primary immunosurveillance of peripheral tissues and highlight the important role of this long-lived cell type in tissue-based immune responses.

Treatment of vitiligo with the topical Janus kinase inhibitor ruxolitinib.

BACKGROUND: Existing therapies for vitiligo are limited in efficacy and can be associated with undesirable side effects. Topical Janus kinase inhibitors may offer a new therapeutic option for vitiligo. OBJECTIVE: We sought to assess the role of topical ruxolitinib 1.5% cream, a Janus kinase inhibitor, in vitiligo treatment. METHODS: This 20-week, open-label, proof-of-concept trial of twice-daily topical ruxolitinib 1.5% cream was conducted in 12 patients with a minimum of 1% affected body surface area of vitiligo. The primary outcome was percent improvement in Vitiligo Area Scoring Index from baseline to week 20. RESULTS: Of 12 patients screened, 11 were enrolled and 9 completed the study (54.5% men; mean age, 52 years). Four patients with significant facial involvement at baseline had a 76% improvement in facial Vitiligo Area Scoring Index scores at week 20 (95% confidence interval, 53-99%; P = .001). A 23% improvement in overall Vitiligo Area Scoring Index scores was observed in all enrolled patients at week 20 (95% confidence interval, 4-43%; P = .02). Three of 8 patients responded on body surfaces and 1 of 8 patients responded on acral surfaces. Adverse events were minor, including erythema, hyperpigmentation, and transient acne. LIMITATIONS: Limitations of the study include the small sample size and open-label study design. CONCLUSIONS: Topical ruxolitinib 1.5% cream provided significant repigmentation in facial vitiligo and may offer a valuable new treatment for vitiligo.

Delayed Second Dose Antibiotics for Patients Admitted From the Emergency Department With Sepsis: Prevalence, Risk Factors, and Outcomes.

OBJECTIVE: 1) Determine frequency and magnitude of delays in second antibiotic administration among patients admitted with sepsis; 2) Identify risk factors for these delays; and 3) Exploratory: determine association between delays and patient-centered outcomes (mortality and mechanical ventilation after second dose). DESIGN: Retrospective, consecutive sample sepsis cohort over 10 months. SETTING: Single, tertiary, academic medical center. PATIENTS: All patients admitted from the emergency department with sepsis or septic shock (defined: infection, ≥ 2 systemic inflammatory response syndrome criteria, hypoperfusion/organ dysfunction) identified by a prospective quality initiative. EXCLUSIONS: less than 18 years old, not receiving initial antibiotics in the emergency department, death before antibiotic redosing, and patient refusing antibiotics. INTERVENTIONS: We determined first-to-second antibiotic time and delay frequency. We considered delay major for first-to-second dose time greater than or equal to 25% of the recommended interval. Factors of interest were demographics, recommended interval length, comorbidities, clinical presentation, location at second dose, initial resuscitative care, and antimicrobial activity mechanism. MEASUREMENTS AND MAIN RESULTS: Of 828 sepsis cases, 272 (33%) had delay greater than or equal to 25%. Delay frequency increased dose dependently with shorter recommended interval: 11 (4%) delays for 24-hour intervals (median time, 18.52 hr); 31 (26%) for 12-hour intervals (median, 10.58 hr); 117 (47%) for 8-hour intervals (median, 9.60 hr); and 113 (72%) for 6-hour intervals (median, 9.55 hr). In multivariable regression, interval length significantly predicted major delay (12 hr: odds ratio, 6.98; CI, 2.33-20.89; 8 hr: odds ratio, 23.70; CI, 8.13-69.11; 6 hr: odds ratio, 71.95; CI, 25.13-206.0). Additional independent risk factors were inpatient boarding in the emergency department (odds ratio, 2.67; CI, 1.74-4.09), initial 3-hour sepsis bundle compliance (odds ratio, 1.57; CI, 1.07-2.30), and older age (odds ratio, 1.16 per 10 yr, CI, 1.01-1.34). In the exploratory multivariable analysis, major delay was associated with increased hospital mortality (odds ratio, 1.61; CI, 1.01-2.57) and mechanical ventilation (odds ratio, 2.44; CI, 1.27-4.69). CONCLUSIONS: Major second dose delays were common, especially for patients given shorter half-life pharmacotherapies and who boarded in the emergency department. They were paradoxically more frequent for patients receiving compliant initial care. We observed association between major second dose delay and increased mortality, length of stay, and mechanical ventilation requirement.

CD/MCD/VTVH-MCD Studies of Escherichia coli Bacterioferritin Support a Binuclear Iron Cofactor Site.

Ferritins and bacterioferritins (Bfrs) utilize a binuclear non-heme iron binding site to catalyze oxidation of Fe(II), leading to formation of an iron mineral core within a protein shell. Unlike ferritins, in which the diiron site binds Fe(II) as a substrate, which then autoxidizes and migrates to the mineral core, the diiron site in Bfr has a 2-His/4-carboxylate ligand set that is commonly found in diiron cofactor enzymes. Bfrs could, therefore, utilize the diiron site as a cofactor rather than for substrate iron binding. In this study, we applied circular dichroism (CD), magnetic CD (MCD), and variable-temperature, variable-field MCD (VTVH-MCD) spectroscopies to define the geometric and electronic structures of the biferrous active site in Escherichia coli Bfr. For these studies, we used an engineered M52L variant, which is known to eliminate binding of a heme cofactor but to have very minor effects on either iron oxidation or mineral core formation. We also examined an H46A/D50A/M52L Bfr variant, which additionally disrupts a previously observed mononuclear non-heme iron binding site inside the protein shell. The spectral analyses define a binuclear and an additional mononuclear ferrous site. The biferrous site shows two different five-coordinate centers. After O2 oxidation and re-reduction, only the mononuclear ferrous signal is eliminated. The retention of the biferrous but not the mononuclear ferrous site upon O2 cycling supports a mechanism in which the binuclear site acts as a cofactor for the O2 reaction, while the mononuclear site binds the substrate Fe(II) that, after its oxidation to Fe(III), migrates to the mineral core.

Human skin is protected by four functionally and phenotypically discrete populations of resident and recirculating memory T cells.

The skin of an adult human contains about 20 billion memory T cells. Epithelial barrier tissues are infiltrated by a combination of resident and recirculating T cells in mice, but the relative proportions and functional activities of resident versus recirculating T cells have not been evaluated in human skin. We discriminated resident from recirculating T cells in human-engrafted mice and lymphoma patients using alemtuzumab, a medication that depletes recirculating T cells from skin, and then analyzed these T cell populations in healthy human skin. All nonrecirculating resident memory T cells (TRM) expressed CD69, but most were CD4(+), CD103(-), and located in the dermis, in contrast to studies in mice. Both CD4(+) and CD8(+) CD103(+) TRM were enriched in the epidermis, had potent effector functions, and had a limited proliferative capacity compared to CD103(-) TRM. TRM of both types had more potent effector functions than recirculating T cells. We observed two distinct populations of recirculating T cells, CCR7(+)/L-selectin(+) central memory T cells (TCM) and CCR7(+)/L-selectin(-) T cells, which we term migratory memory T cells (TMM). Circulating skin-tropic TMM were intermediate in cytokine production between TCM and effector memory T cells. In patients with cutaneous T cell lymphoma, malignant TCM and TMM induced distinct inflammatory skin lesions, and TMM were depleted more slowly from skin after alemtuzumab, suggesting that TMM may recirculate more slowly. In summary, human skin is protected by four functionally distinct populations of T cells, two resident and two recirculating, with differing territories of migration and distinct functional activities.