Lymphadenopathy and lymph node rejection following facial vascularized composite allotransplantation

BACKGROUND

Apart from the skin, little is known about the immunological processes in deeper tissues, which are typically not accessible to biopsy and inspection, of vascularized composite allografts (VCAs). Face transplant patients develop prominent adenopathy shortly after transplantation that resolves over time. The mechanisms underlying this process are not understood.

MATERIALS AND METHODS

A retrospective cohort study was conducted on 9 patients who underwent 10 facial VCAs at the Brigham and Women's Hospital, Boston, MA, between April 2009 and July 2019. Clinical, radiological, and histological data related to lymphadenopathy of the head and neck were reviewed.

RESULTS

Patients who received donor-derived lymph nodes (LNs) developed bilateral lymphadenopathy of the submental or submandibular superficial LNs. Median time of presentation was POD18 (range POD6-POM3). Notably, bilateral adenopathy of the neck was not observed in later stages of follow-up (mean follow-up, 115 months). Histology of 3 LNs showed increased histiocytes and apoptosis, with the features reminiscent of necrotizing histiocytic lymphadenitis, and B and T lymphocytes (mostly CD8 + T) admixed with CD163 + histiocytes and dendritic cells. Molecular chimerism analysis in one case showed the coexistence of donor (81%) and recipient (19%) derived lymphocytes. Granzyme B (GZMB) expression confirmed the presence of increased cytotoxic T cells in this LN sample.

CONCLUSION

Our data suggested the involvement of an immunological process within the donor-derived LNs after facial allotransplantation between the recipient and donor cells. GZMB expression suggested LN rejection that can occurred independently of skin rejection. This finding supports the need to better define the role of donor-derived immune cells in the context of allograft rejection.

Epstein-Barr Virus Orchestrates Spatial Reorganization and Immunomodulation within the Classic Hodgkin Lymphoma Tumor Microenvironment

Classic Hodgkin Lymphoma (cHL) is a tumor composed of rare malignant Hodgkin and Reed-Sternberg (HRS) cells nested within a T-cell rich inflammatory immune infiltrate. cHL is associated with Epstein-Barr Virus (EBV) in 25% of cases. The specific contributions of EBV to the pathogenesis of cHL remain largely unknown, in part due to technical barriers in dissecting the tumor microenvironment (TME) in high detail. Herein, we applied multiplexed ion beam imaging (MIBI) spatial pro-teomics on 6 EBV-positive and 14 EBV-negative cHL samples. We identify key TME features that distinguish between EBV-positive and EBV-negative cHL, including the relative predominance of memory CD8 T cells and increased T-cell dysfunction as a function of spatial proximity to HRS cells. Building upon a larger multi-institutional cohort of 22 EBV-positive and 24 EBV-negative cHL samples, we orthogonally validated our findings through a spatial multi-omics approach, coupling whole transcriptome capture with antibody-defined cell types for tu-mor and T-cell populations within the cHL TME. We delineate contrasting transcriptomic immunological signatures between EBV-positive and EBV-negative cases that differently impact HRS cell proliferation, tumor-immune interactions, and mecha-nisms of T-cell dysregulation and dysfunction. Our multi-modal framework enabled a comprehensive dissection of EBV-linked reorganization and immune evasion within the cHL TME, and highlighted the need to elucidate the cellular and molecular fac-tors of virus-associated tumors, with potential for targeted therapeutic strategies.

Cutaneous Manifestations of Myeloid Neoplasms Exhibit Broad and Divergent Morphologic and Immunophenotypic Features but Share Ancestral Clonal Mutations With Bone Marrow

In this study, we performed a comprehensive molecular analysis of paired skin and peripheral blood/bone marrow (BM) samples from 17 patients with cutaneous myeloid or cutaneous histiocytic-dendritic neoplasms. The cutaneous manifestations included 10 patients with cutaneous acute myeloid leukemia (c-AML), 2 patients with full or partial Langerhans cell differentiation, 2 patients with blastic plasmacytoid dendritic cell neoplasms (BPDCN), 1 patient with both Langerhans cell differentiation and BPDCN, and 2 patients with full or partial indeterminate dendritic cell differentiation. Seven of the 10 c-AML patients (70%) exhibited concurrent or subsequent marrow involvement by acute myeloid leukemia, with all 7 cases (100%) demonstrating shared clonal mutations in both the skin and BM. However, clonal relatedness was documented in one additional case that never had any BM involvement. Nevertheless, NPM1 mutations were identified in 7 of the 10 (70%) of these c-AML cases while one had KMT2A rearrangement and one showed inv(16). All 3 patients (100%) with Langerhans cell neoplasms, 2 patients with BPDCN (100%), and one of the 2 patients (50%) with other cutaneous dendritic cell neoplasms also demonstrated shared mutations between the skin and concurrent or subsequent myeloid neoplasms. Both BM and c-AML shared identical founding drivers, with a predominance of NPM1, DNMT3A, and translocations associated with monocytic differentiation, with common cutaneous-only mutations involving genes in the signal transduction and epigenetic pathways. Cutaneous histiocytic-dendritic neoplasms shared founding drivers in ASXL1, TET2, and/or SRSF2. However, in the Langerhans cell histiocytosis or histiocytic sarcoma cases, there exist recurrent secondary RAS pathway hits, whereas cutaneous BPDCN cases exhibit copy number or structural variants. These results enrich and broaden our understanding of clonally related cutaneous manifestations of myeloid neoplasms and further illuminate the highly diverse spectrum of morphologic and immunophenotypic features they exhibit.

Cellular activation pathways and interaction networks in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) is an evolving field of reconstructive surgery that has revolutionized the treatment of patients with devastating injuries, including those with limb losses or facial disfigurement. The transplanted units are typically comprised of different tissue types, including skin, mucosa, blood and lymphatic vasculature, muscle, and bone. It is widely accepted that the antigenicity of some VCA components, such as skin, is particularly potent in eliciting a strong recipient rejection response following transplantation. The fine line between tolerance and rejection of the graft is orchestrated by different cell types, including both donor and recipient-derived lymphocytes, macrophages, and other immune and donor-derived tissue cells (e.g., endothelium). Here, we delineate the role of different cell and tissue types during VCA rejection. Rejection of VCA grafts and the necessity of life-long multidrug immunosuppression remains one of the major challenges in this field. This review sheds light on recent developments in decoding the cellular signature of graft rejection in VCA and how these may, ultimately, influence the clinical management of VCA patients by way of novel therapies that target specific cellular processes.

Expanding the Immunophenotypic Spectrum of Neoplastic and Reactive Plasmacytoid Dendritic Cells

OBJECTIVES

Targeted therapies for blastic plasmacytoid dendritic cell neoplasm (BPDCN) have presented a diagnostic dilemma for differentiating residual BPDCN from reactive plasmacytoid dendritic cells (pDCs) because these conditions have a similar immunoprofile, necessitating discovery of additional diagnostic markers.

METHODS

Fifty cases of BPDCN involving bone marrow (26/50) and skin (24/50) as well as other hematologic malignancies (67) and nonneoplastic samples (37) were included. Slides were stained using a double-staining protocol for the following immunohistochemical marker combinations: TCF4/CD123, TCF4/CD56, SOX4/CD123, and IRF8/CD123.

RESULTS

The nuclear marker SOX4 is expressed in neoplastic pDCs; in our cohort, SOX4/CD123 showed 100% sensitivity and 98% specificity in distinguishing BPDCN from reactive pDCs and other neoplasms. TCF4/CD56 had a 96% sensitivity and 100% specificity for BPDCN. IRF8 is a nonspecific marker that is positive in BPDCN and pDCs as well as other myeloid malignancies.

CONCLUSIONS

The novel immunohistochemical combination SOX4/CD123 distinguishes BPDCN, including CD56-negative BPDCN, from both reactive pDCs and other neoplasms. Because of their high diagnostic sensitivity and specificity, the double-staining marker combinations TCF4/CD123, TCF4/CD56, and SOX4/CD123 can be used to confirm lineage in BPDCN cases and detect minimal/measurable residual disease in tissue specimens.

Hematopathology of SARS-CoV-2 infection and COVID-19 disease

Coronavirus disease 2019 is caused by severe acute respiratory syndrome coronavirus 2 and is associated with pronounced hematopathologic findings. Peripheral blood features are heterogeneous and very often include neutrophilia, lymphopenia, myeloid left shift, abnormally segmented neutrophils, atypical lymphocytes/plasmacytoid lymphocytes, and atypical monocytes. Bone marrow biopsies and aspirates are often notable for histiocytosis and hemophagocytosis, whereas secondary lymphoid organs may exhibit lymphocyte depletion, pronounced plasmacytoid infiltrates, and hemophagocytosis. These changes are reflective of profound innate and adaptive immune dysregulation, and ongoing research efforts continue to identify clinically applicable biomarkers of disease severity and outcome.

Primary Central Nervous System Anaplastic Large Cell Lymphoma, ALK Positive

OBJECTIVES

Primary central nervous system anaplastic large cell lymphoma, anaplastic lymphoma kinase positive (primary CNS ALCL, ALK+) is a rare CNS lymphoma whose description is limited to case reports. These tumors have a variable clinical course, and prognosis is primarily determined by age. We present the largest case series to date of primary CNS ALCL, ALK+, with observational data.

METHODS

A retrospective search of multiple academic centers was performed to identify cases of primary CNS ALCL, ALK+. We also performed a review of published cases of primary CNS ALCL, ALK+. Clinical history, radiography, pathology, and genetic testing data were obtained to determine the prognostic implications in the context of clinical course.

RESULTS

We identified three cases of primary CNS ALCL, ALK+ from our databases. A literature review identified 30 published reports of 31 individual cases. Clinical features for the combined 34 cases included a median age of 18.5 years, with a male to female ratio of 4.7:1, and the most common symptom was headache. Genetic studies demonstrated an ALK rearrangement by fluorescence in situ hybridization, and a gene fusion assay confirmed an NPM1-ALK gene fusion in one case.

CONCLUSIONS

We present the largest case series to date of a rare primary CNS lymphoma with additional diagnostic and clinical information.

Non-Hodgkin lymphoma mimicking acute leukemia: a report of six cases and review of the literature

Aggressive subtypes of non-Hodgkin lymphoma may uncommonly be referred to clinical oncologists for treatment of acute leukemia, due to an elevated or rapidly rising white blood cell count (WBC), with circulating neoplastic cells that morphologically resemble leukemic blasts seen in acute myeloid or lymphoblastic leukemia. We describe six cases of non-Hodgkin lymphoma that mimicked acute leukemia and were identified in the pathology records of the Brigham and Women's Hospital. The patients were older adults (mean age 70 years), who presented with leukocytosis (mean 79.7 × 10⁹/L) with circulating neoplastic cells (mean 57%), which mimicked leukemic blasts, thrombocytopenia, and anemia (4/6 patients). In each case, immunophenotypic analysis identified a population of mature B cells or mature T cells. We identified 15 additional cases of non-Hodgkin lymphoma in the literature that mimicked acute leukemia; considering all 21 cases, 11 had an appearance of acute lymphoblastic leukemia, 4 had an appearance of acute monocytic leukemia, and 6 had an appearance of acute leukemia unable to be further categorized. In general, patients exhibited poor overall survival. These cases illustrate the importance of comprehensive immunophenotypic analysis in the initial evaluation of hematolymphoid neoplasms, and that occasional cases of non-Hodgkin lymphomas can resemble acute leukemia at initial presentation.

Molecular Pathology of Myeloid Neoplasms: Molecular Pattern Recognition

Despite the apparent complexity of the molecular genetic underpinnings of myeloid neoplasms, most myeloid mutational profiles can be understood within a simple framework. Somatic mutations accumulate in hematopoietic stem cells with aging and toxic insults, termed clonal hematopoiesis. These "old stem cells" mutations, predominantly in the epigenetic and RNA spliceosome pathways, act as "founding" driver mutations leading to a clonal myeloid neoplasm when sufficient in number and clone size. Subsequent mutations can create the genetic flavor of the myeloid neoplasm ("backseat" drivers) due to their enrichment in certain entities or act as progression events ("aggressive" drivers) during clonal evolution.

Histiocytic and Dendritic Cell Sarcomas of Hematopoietic Origin Share Targetable Genomic Alterations Distinct from Follicular Dendritic Cell Sarcoma

Background

Histiocytic and dendritic cell neoplasms are a diverse group of tumors arising from monocytic or dendritic cell lineage. Whereas the genomic features for Langerhans cell histiocytosis and Erdheim‐Chester disease have been well described, other less common and often aggressive tumors in this broad category remain poorly characterized, and comparison studies across the World Health Organization diagnostic categories are lacking.

Methods

Tumor samples from a total of 102 patient cases within four major subtypes of malignant histiocytic and dendritic cell neoplasms, including 44 follicular dendritic cell sarcomas (FDCSs), 41 histiocytic sarcomas (HSs), 7 interdigitating dendritic cell sarcomas (IDCSs), and 10 Langerhans cell sarcomas (LCSs), underwent hybridization capture with analysis of up to 406 cancer‐related genes.

Results

Among the entire cohort of 102 patients, CDKN2A mutations were most frequent across subtypes and made up 32% of cases, followed by TP53 mutations (22%). Mitogen‐activated protein kinase (MAPK) pathway mutations were present and enriched among the malignant histiocytosis (M) group (HS, IDCS, and LCS) but absent in FDCS (72% vs. 0%; p < .0001). In contrast, NF‐κB pathway mutations were frequent in FDCSs but rare in M group histiocytoses (61% vs. 12%; p < .0001). Tumor mutational burden was significantly higher in M group histiocytoses as compared with FDCSs (median 4.0/Mb vs. 2.4/Mb; p = .012). We also describe a pediatric patient with recurrent secondary histiocytic sarcoma treated with targeted therapy and interrogated by molecular analysis to identify mechanisms of therapeutic resistance.

Conclusion

A total of 42 patient tumors (41%) harbored pathogenic mutations that were potentially targetable by approved and/or investigative therapies. Our findings highlight the potential value of molecular testing to enable precise tumor classification, identify candidate oncogenic drivers, and define personalized therapeutic options for patients with these aggressive tumors.

Implications for Practice

This study presents comprehensive genomic profiling results on 102 patient cases within four major subtypes of malignant histiocytic and dendritic cell neoplasms, including 44 follicular dendritic cell sarcomas (FDCSs), 41 histiocytic sarcomas (HSs), 7 interdigitating dendritic cell sarcomas (IDCSs), and 10 Langerhans cell sarcomas (LCSs). MAPK pathway mutations were present and enriched among the malignant histiocytosis (M) group (HS, IDCS, and LCS) but absent in FDCSs. In contrast, NF‐κB pathway mutations were frequent in FDCSs but rare in M group histiocytosis. A total of 42 patient tumors (41%) harbored pathogenic mutations that were potentially targetable by approved and/or investigative therapies.

Histiocytic and dendritic cell neoplasms are a diverse group of tumors arising from the monocytic or dendritic cell lineage. This article presents the molecular characteristics of the four major subtypes of malignant histiocytic and dendritic cell neoplasms, focusing on genomic alterations that could represent therapeutic targets.

Tonsillar p16-Positive Follicular Dendritic Cell Sarcoma Mimicking HPV-Related Oropharyngeal Squamous Cell Carcinoma: A Case Report and Review of Reported Cases

Follicular dendritic cell sarcoma (FDCS) is a rare entity which can share morphologic features with non-keratinizing squamous cell carcinoma. Recent reports suggest that up to half of FDCSs show immunohistochemical positivity for p16 (Zhang et al., in Hum Pathol 66:40-47, 2017), a stain that is conventionally used in the risk stratification of oropharyngeal squamous cell carcinoma (OPSCC). Herein, we report a case of p16-positive FDCS with clinical and histomorphologic overlap with human papilloma virus (HPV)-related OPSCC.

Pulmonary adenomyoma presenting as a right cardiophrenic angle mass

Pulmonary adenomyomas are rare adenomyomatous hamartomas. In the few cases described in the literature, these benign tumors are encapsulated by lung parenchyma. We describe a case of a 59 year-old woman with acetylcholine receptor antibody-negative myasthenia gravis and a right cardiophrenic mass initially thought to be a thymoma. Histopathology surprisingly revealed a pulmonary adenomyoma which involved the mediastinal fat at the cardiophrenic angle.

Differences in PD-L1-Expressing Macrophages and Immune Microenvironment in Testicular Germ Cell Tumors

OBJECTIVES

To characterize the tumor microenvironment of testicular germ cell tumors (GCTs) using immunohistochemical markers.

METHODS

Seventy-seven orchiectomies, including 36 nonmetastatic (NM) seminomas, 15 metastatic (M) seminomas, 13 nonmetastatic nonseminomatous germ cell tumors (NSGCTs), and 13 metastatic NSGCTs, were studied with PD-1, PD-L1, FOXP3, CD68, CD163, and mismatch repair (MMR) immunohistochemistry. FOXP3+ and PD-1+ tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs) expressing CD68 and CD163 were enumerated. PDL-1 expression was evaluated on tumor cells and macrophages.

RESULTS

GCTs primarily express PD-L1 on TAMs, except choriocarcinoma, where true tumor cell positivity was noted. Seminomas reveal increased intratumoral PD-L1+ TAMs compared with NSGCTs (P < .05). Activated TILs are increased in NM-seminomas compared with M-seminomas (P < .05). All GCTs retained MMR expression.

CONCLUSIONS

Robust PD-L1+ TAMs are significantly expanded in seminomas compared with NSGCTs. Among all GCTs, only choriocarcinoma cells reveal true positivity for PD-L1. These findings expand the realm of potentially targeted treatments for GCTs.

Cyclin D1 expression and novel mutational findings in Rosai-Dorfman disease

Rosai-Dorfman disease (RDD) is an enigmatic histiocytic disorder classically diagnosed by a distinctive combination of pathological features: emperipolesis, or migration of intact haematological cells through the voluminous cytoplasm of lesional histiocytes, and expression of S100 by these histiocytes. The pathogenesis has long been elusive until the recent detection of recurrent and mutually exclusive mutations in several oncogenes in the mitogen-activated protein kinase (MAPK) pathway. Based on these findings, we investigated a cohort of 21 RDD patients and found that the lesional histiocytes in 86% (18/21) of patients exhibited strong and diffuse nuclear Cyclin D1 expression, which not only may provide a diagnostic marker for this sometimes pathologically challenging disease, but also probably reflects constitutive MAPK pathway activation because we additionally identified phosphorylated-ERK expression in 90% (19/21) of cases. Further, we performed massively parallel sequencing on a subset (6/18) of the CyclinD1 positive cases, identifying several mutations that have not been previously reported in RDD. Taken together, our findings bolster the concept of RDD as a disease of MAPK activation in a substantial percentage of cases and enhance the current understanding of the pathogenesis of RDD.

Hematopoietic neoplasms with 9p24/JAK2 rearrangement: a multicenter study

The purpose of this study is to examine hematopoietic neoplasms with 9p24/JAK2 rearrangement including neoplasms associated with t(8;9)(p22;p24)/PCM1-JAK2 fusion neoplasm as well as cases with translocations involving 9p24/JAK2 and other partner genes. From seven large medical centers, we identified ten patients with t(8;9)(p22;p24) /PCM1-JAK2 and 3 with t(9p24;v)/JAK2 at diagnosis. Majority of the cases showed myeloproliferative neoplasm (MPN) associated features (n = 7) characterized by variable degrees of eosinophilia, myelofibrosis, frequent proliferations of early erythroblasts in bone marrow and extramedullary sites, and infrequent/absent somatic mutations. Other less common presentations included myelodysplastic syndromes (MDS) or MDS/MPN (one each). Four patients presented with B-lymphoblastic leukemia (B-ALL), and of them, two patients with t(8;9)(p22;p24.1) were proven to be B-lymphoblastic crisis of MPN; and the other two cases with t(9p24;v) both were de novo B-ALL, BCR-ABL1-like (Ph-like). We show that the hematopoietic neoplasms with 9p24/JAK2 rearrangement are extremely rare, and most of them are associated with t(8;9)(p22;p24)/PCM1-JAK2, a recent provisional World Health Organization entity under "myeloid/lymphoid neoplasm with a specific gene rearrangement". Cases of t(8;9)(p22;p24)/PCM1-JAK2, though heterogeneous, do exhibit some common clinicopathological characteristic features. Cases with t(9p24;v)/JAK2 are extremely rare; while such cases with a MPN presentation may resemble t(8;9)(p22;p24.1)/PCM1-JAK2, B-ALL cases presenting de novo B-ALL might belong to Ph-like B-ALL.

A Rare Case of an Osteolytic Bone-infarct-associated Osteosarcoma: Case Report with Radiographic and Histopathologic Correlation, and Literature Review

Benign lesions such as Paget’s disease of the bone, enchondroma, osteochondromas, chronic osteomyelitis/infections and bone infarcts may rarely undergo malignant degeneration/transformation into sarcomas. To date, only 14 prior bone infarct-associated osteosarcomas have been described, with just two being primarily osteolytic. We discuss a case of a patient with a humeral bone-infarct, who presented with a presumed benign pathological fracture of the humerus through the bone infarct. Subsequent imaging and biopsy showed that there was a malignant degeneration into a primarily osteolytic osteosarcoma. We review the patient’s presentation, radiographic and histologic appearance of the osteosarcoma and discuss the epidemiology, surgical and non-surgical treatment and surveillance of bone-infarct-associated osteosarcomas.

Primary malignant perivascular epithelioid cell neoplasm (PEComa) of the bone mimicking granular cell tumor in core biopsy: A case report and literature review

The present study investigated the case of a 46-year-old female with primary malignant perivascular epithelioid cell neoplasm (PEComa) of the femur. The patient presented with a 5-month history of right distal thigh pain following trauma. Radiographs of the right distal femur revealed a mixed lytic and sclerotic lesion with subtle areas of cortical destruction and soft tissue extension, consistent with an aggressive tumor. A core biopsy revealed an epithelioid tumor with granular cell features, but a definitive diagnosis could not be made. Due to the aggressive features on radiologic evaluation, the patient underwent a resection of the distal femur and reconstruction with a distal femoral megaprosthesis and hinged knee replacement. The post-resection pathology led to a final diagnosis of primary bone PEComa, with histologic features including epithelioid, granular cell and spindled cell morphologies and biphasic immunoreactivity for melanocytic and smooth muscle markers. The large tumor size (>5 cm), rapid mitotic rate, infiltrative growth pattern, high nuclear grade and cellularity, and the presence of necrosis rendered this a malignant PEComa. The present study discussed the case, including radiographic (radiographs, magnetic resonance imaging and positron emission tomography scans) and histologic appearance and a literature review.

Imaging Lenticular Autofluorescence in Older Subjects

Purpose

To evaluate whether a practical method of imaging lenticular autofluorescence (AF) can provide an individualized measure correlated with age-related lens yellowing in older subjects undergoing tests involving shorter wavelength lights.

Methods

Lenticular AF was imaged with 488-nm excitation using a confocal scanning laser ophthalmoscope (cSLO) routinely used for retinal AF imaging. There were 75 older subjects (ages 47–87) at two sites; a small cohort of younger subjects served as controls. At one site, the cSLO was equipped with an internal reference to allow quantitative AF measurements; at the other site, reduced-illuminance AF imaging (RAFI) was used. In a subset of subjects, lens density index was independently estimated from dark-adapted spectral sensitivities performed psychophysically.

Results

Lenticular AF intensity was significantly higher in the older eyes than the younger cohort when measured with the internal reference (59.2 ± 15.4 vs. 134.4 ± 31.7 gray levels; P < 0.05) as well as when recorded with RAFI without the internal reference (10.9 ± 1.5 vs. 26.1 ± 5.7 gray levels; P < 0.05). Lenticular AF was positively correlated with age; however, there could also be large differences between individuals of similar age. Lenticular AF intensity correlated well with lens density indices estimated from psychophysical measures.

Conclusions

Lenticular AF measured with a retinal cSLO can provide a practical and individualized measure of lens yellowing, and may be a good candidate to distinguish between preretinal and retinal deficits involving short-wavelength lights in older eyes.

Pseudo-fovea formation after gene therapy for RPE65-LCA

PURPOSE

The purpose of this study was to evaluate fixation location and oculomotor characteristics of 15 patients with Leber congenital amaurosis (LCA) caused by RPE65 mutations (RPE65-LCA) who underwent retinal gene therapy.

METHODS

Eye movements were quantified under infrared imaging of the retina while the subject fixated on a stationary target. In a subset of patients, letter recognition under retinal imaging was performed. Cortical responses to visual stimulation were measured using functional magnetic resonance imaging (fMRI) in two patients before and after therapy.

RESULTS

All patients were able to fixate on a 1° diameter visible target in the dark. The preferred retinal locus of fixation was either at the anatomical fovea or at an extrafoveal locus. There were a wide range of oculomotor abnormalities. Natural history showed little change in oculomotor abnormalities if target illuminance was increased to maintain target visibility as the disease progressed. Eleven of 15 study eyes treated with gene therapy showed no differences from baseline fixation locations or instability over an average of follow-up of 3.5 years. Four of 15 eyes developed new pseudo-foveas in the treated retinal regions 9 to 12 months after therapy that persisted for up to 6 years; patients used their pseudo-foveas for letter identification. fMRI studies demonstrated that preservation of light sensitivity was restricted to the cortical projection zone of the pseudo-foveas.

CONCLUSIONS

The slow emergence of pseudo-foveas many months after the initial increases in light sensitivity points to a substantial plasticity of the adult visual system and a complex interaction between it and the progression of underlying retinal disease. The visual significance of pseudo-foveas suggests careful consideration of treatment zones for future gene therapy trials. (ClinicalTrials.gov number, NCT00481546.).

Drusen and photoreceptor abnormalities in African-Americans with intermediate non-neovascular age-related macular degeneration

PURPOSE/AIM

To investigate the relationship of drusen and photoreceptor abnormalities in African-American (AA) patients with intermediate non-neovascular age-related macular degeneration (AMD).

MATERIALS AND METHODS

AA patients with intermediate AMD (n = 11; age 52-77 years) were studied with spectral-domain optical coherence tomography. Macular location and characteristics of large drusen (≥125 µm) were determined. Thickness of photoreceptor laminae was quantified overlying drusen and in other macular regions. A patient with advanced AMD (age 87) was included to illustrate the disease spectrum.

RESULTS

In this AA patient cohort, the spectrum of changes known to occur in AMD, including large drusen, sub-retinal drusenoid deposits and geographic atrophy, were identified. In intermediate AMD eyes (n = 17), there were 183 large drusen, the majority of which were pericentral in location. Overlying the drusen there was significant thinning of the photoreceptor outer nuclear layer (termed ONL(+)) as well as the inner and outer segments (IS + OS). The reductions in IS + OS thickness were directly related to ONL(+) thickness. In a fraction (∼8%) of paradrusen locations with normal lamination sampled within ∼280 µm of peak drusen height, ONL(+) was significantly thickened compared to age and retinal-location-matched normal values. Topographical maps of the macula confirmed ONL thickening in regions neighboring and distant to large drusen.

CONCLUSIONS

We confirm there is a pericentral distribution of drusen across AA-AMD maculae rather than the central localization in Caucasian AMD. Reductions in the photoreceptor laminae overlying drusen are evident. ONL(+) thickening in some macular areas of AA-AMD eyes may be an early phenotypic marker for photoreceptor stress.

Determining consequences of retinal membrane guanylyl cyclase (RetGC1) deficiency in human Leber congenital amaurosis en route to therapy: residual cone-photoreceptor vision correlates with biochemical properties of the mutants

The GUCY2D gene encodes retinal membrane guanylyl cyclase (RetGC1), a key component of the phototransduction machinery in photoreceptors. Mutations in GUCY2D cause Leber congenital amaurosis type 1 (LCA1), an autosomal recessive human retinal blinding disease. The effects of RetGC1 deficiency on human rod and cone photoreceptor structure and function are currently unknown. To move LCA1 closer to clinical trials, we characterized a cohort of patients (ages 6 months-37 years) with GUCY2D mutations. In vivo analyses of retinal architecture indicated intact rod photoreceptors in all patients but abnormalities in foveal cones. By functional phenotype, there were patients with and those without detectable cone vision. Rod vision could be retained and did not correlate with the extent of cone vision or age. In patients without cone vision, rod vision functioned unsaturated under bright ambient illumination. In vitro analyses of the mutant alleles showed that in addition to the major truncation of the essential catalytic domain in RetGC1, some missense mutations in LCA1 patients result in a severe loss of function by inactivating its catalytic activity and/or ability to interact with the activator proteins, GCAPs. The differences in rod sensitivities among patients were not explained by the biochemical properties of the mutants. However, the RetGC1 mutant alleles with remaining biochemical activity in vitro were associated with retained cone vision in vivo. We postulate a relationship between the level of RetGC1 activity and the degree of cone vision abnormality, and argue for cone function being the efficacy outcome in clinical trials of gene augmentation therapy in LCA1.

RPGR-associated retinal degeneration in human X-linked RP and a murine model

PURPOSE

We investigated the retinal disease due to mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in human patients and in an Rpgr conditional knockout (cko) mouse model.

METHODS

XLRP patients with RPGR-ORF15 mutations (n = 35, ages at first visit 5-72 years) had clinical examinations, and rod and cone perimetry. Rpgr-cko mice, in which the proximal promoter and first exon were deleted ubiquitously, were back-crossed onto a BALB/c background, and studied with optical coherence tomography and electroretinography (ERG). Retinal histopathology was performed on a subset.

RESULTS

Different patterns of rod and cone dysfunction were present in patients. Frequently, there were midperipheral losses with residual rod and cone function in central and peripheral retina. Longitudinal data indicated that central rod loss preceded peripheral rod losses. Central cone-only vision with no peripheral function was a late stage. Less commonly, patients had central rod and cone dysfunction, but preserved, albeit abnormal, midperipheral rod and cone vision. Rpgr-cko mice had progressive retinal degeneration detectable in the first months of life. ERGs indicated relatively equal rod and cone disease. At late stages, there was greater inferior versus superior retinal degeneration.

CONCLUSIONS

RPGR mutations lead to progressive loss of rod and cone vision, but show different patterns of residual photoreceptor disease expression. Knowledge of the patterns should guide treatment strategies. Rpgr-cko mice had onset of degeneration at relatively young ages and progressive photoreceptor disease. The natural history in this model will permit preclinical proof-of-concept studies to be designed and such studies should advance progress toward human therapy.

Affinity maturation and isotype switch in clonally related anti-erythrocyte autoantibodies

The NZB mouse is genetically predisposed to develop, at approximately 6 months of age, a spontaneous and severe autoimmune anaemia caused by production of pathogenic anti-mouse erythrocyte autoantibodies. Molecular analysis of a panel of five anti-erythrocyte monoclonal antibodies (MoAb) derived from splenocytes of unimmunized NZB mice revealed that these autoantibodies all had functionally rearranged genes from the VH J558 family of immunoglobulin genes with closest homology to germline genes H10 and H30. Owing to clustering of nucleotide differences within the CDRs, compared with the germline, it was concluded that these antibodies were most likely generated by an antigen-driven mechanism. We report here further molecular analysis of two (4.16.1 and B4.13.2) of the panel of five anti-mouse erythrocyte producing hybridomas which are apparently clonally related. Nucleotide analysis of the light chain cDNA indicated that both antibodies had closest homology to germline gene V kappa 24 and use J kappa 2 gene. Determination of the functional affinities of the MoAb reveal that B4.13.2 (IgG2a) has a > 10-fold higher affinity for mouse erythrocytes when compared to 4.16.1 (IgG1). This finding supports the view that these two autoantibodies are generated by an antigen-driven mechanism. The proposed mechanism would involve the selection and expansion of a small population of B-lymphocytes by antigen leading to isotype switch, somatic mutation and increased affinity. Our data also point to the possibility that some framework residues may be involved in the binding to antigen.

Identification of hybridomas derived from mouse CD5+ B lymphocytes by fluorescent staining for cytoplasmic CD5 expression

The production of hybridomas derived from CD5+ B lymphocytes is important for studying the immunoglobulin gene repertoire and antibody specificity of this B-lymphocyte subpopulation. However, hybridomas derived from these lymphocytes invariably lose surface membrane expression of CD5 following hybridization. This impedes the unequivocal assignment of the generated hybridomas to the CD5+ B-lymphocyte subpopulation from unsorted, or partially sorted, cells. Recent studies have shown that mRNA transcripts of the CD5 gene and the protein product can be detected in the cytoplasm of some mouse hybridomas, indicating that although surface expression has been lost, they may have been generated from CD5+ B lymphocytes. These studies, however, have been unable to discount completely the possibility that aberrant cytoplasmic expression of the CD5 gene occurred as a direct consequence of the hybridization process. To confirm that cytoplasmic CD5 expression in the hybridomas is in fact directly related to the B-lymphocyte origin we have generated hybridomas from FACS-sorted CD5+ and CD5- murine splenic B lymphocytes, and determined their surface and cytoplasmic CD5 expression by fluorescence-activated cell sorting. Our findings reveal that all hybridomas derived from CD5+ B lymphocytes (nine hybridomas) were negative for surface but positive for cytoplasmic CD5 expression, whereas all hybridomas derived from CD5- B lymphocytes (nine hybridomas) were negative for both surface and cytoplasmic CD5 expression. This finding shows that staining for cytoplasmic CD5 expression provides an accurate method of determining the cellular origin of murine B-lymphocyte hybridomas.

Anti-mouse red blood cell monoclonal antibodies use functionally rearranged genes from the VH J558 family and are derived from the CD5- B-lymphocyte subpopulation

The NZB mouse strain is genetically predisposed to develop, at approximately 6 months of age, a spontaneous and severe autoimmune anaemia caused by the production of pathogenic anti-mouse red blood cell (MRBC) autoantibodies. Although it is believed that the predisposition to autoimmune anaemia is multigenic in nature, the main pathogenic mechanism is attributed to anti-MRBC autoantibodies. We have generated eight anti-MRBC monoclonal antibody (mAb)-producing hybridomas derived from splenocytes of 9- and 12-month-old NZB mice with spontaneous autoimmune anaemia to dissect the molecular and cellular mechanisms resulting in the production of these pathogenic antibodies. The predominant immunoglobulin isotype was IgG2a, produced by five out of eight hybridomas (63%), while IgM, IgG1 and IgG2b were each produced by one hybridoma cell line (12%). Antigen specificity analysis of all eight hybridomas revealed that antibodies from seven out of eight hybridomas were monospecific for MRBC antigen(s). Only one hybridoma (clone 4-16-1) cross-reacted with rat RBC. None of the hybridomas produced antibodies reactive with single- or double-stranded DNA (ss- or dsDNA). Surface and cytoplasmic staining for the CD5 antigen revealed that none of the hybridomas was derived from CD5+ B lymphocytes. All hybridomas cause anaemia when implanted intraperitoneally into normal BALB/c mice. Molecular studies of five of the eight anti-MRBC mAb reveal that all use functionally rearranged genes from the VH J558 gene family. Three of these five mAb used FL16.1 DH genes while one had a CDR3 that resulted from a fusion between two DH genes (SP2.3 and SP2.2) from the SP family.

Molecular mechanisms resulting in pathogenic anti-mouse erythrocyte antibodies in New Zealand black mice

The New Zealand black (NZB) mouse strain is genetically predisposed to develop, at approximately 6 months of age, a spontaneous and severe autoimmune anaemia caused by production of pathogenic anti-mouse erythrocyte autoantibodies. In order to investigate the molecular mechanisms which lead to anti-mouse erythrocyte autoantibody production we have generated eight anti-mouse erythrocyte MoAbs producing hybridomas from splenocytes of 9- and 12-month-old NZB with spontaneous autoimmune anaemia. IgG2a was the predominant isotype, while IgM, IgG1 and IgG2b were each produced by one hybridoma cell line. All anti-mouse erythrocyte MoAbs were characterized for their antigen specificities. None of the MoAbs cross-reacted with ss- or dsDNA or with other species' erythrocytes, with the exception of one MoAb which cross-reacted with rat erythrocytes. None of the eight hybridomas was demonstrated to express surface or cytoplasmic CD5, suggesting that they derived from CD5- B lymphocytes. All hybridomas when implanted intraperitoneally into BALB/c mice caused anaemia. In order to define the genetic basis and investigate the molecular mechanisms resulting in pathogenic anti-mouse erythrocyte autoantibody production, the pattern of immunoglobulin variable region gene use has been studied. Five of the eight MoAbs whose IgVH genes were sequenced all have functionally rearranged genes from the VH J558 gene family. There is evidence for somatic point mutations in the complementarity-determining regions (CDR) of the IgVH genes in all of these five MoAbs when compared with the closest known germline gene. We suggest that these nucleotide sequence changes are likely to reflect selection by an antigen-driven mechanism. Furthermore, the data indicate that pathogenic anti-mouse erythrocytes are not derived from 'natural' autoantibodies.