Xiaoqi Lin

Administration of Agonistic Anti-4-1BB Monoclonal Antibody Leads to the Amelioration of Experimental Autoimmune Encephalomyelitis

4-1BB, a member of the TNFR superfamily, is a costimulatory receptor primarily expressed on activated T cells. It has been shown that the administration of agonistic anti-4-1BB Abs enhances tumor immunity and allogenic immune responses. Paradoxically, we found that the administration of an agonistic anti-4-1BB mAb (2A) dramatically reduced the incidence and severity of experimental autoimmune encephalomyelitis (EAE). Adoptive transfer of T cells from such treated mice failed to induce EAE, whereas anti-4-1BB treatment following adoptive transfer of encephalitogenic T cells did not prevent EAE pathogenesis. These results suggest that anti-4-1BB treatment during the induction phase inhibits autoreactive T cell immune responses rather than preventing T cell trafficking into the CNS. This was substantiated by the observations that draining lymph node cells from anti-4-1BB-treated mice failed to respond to Ag stimulation in vitro. In addition, we found that such treatment initially promotes the activation and proliferation of Ag-specific CD4+ T cells but subsequently increases their probability of undergoing activation-induced cell death, thereby inhibiting effector T cell responses. More importantly, 2A treatment also inhibits the relapse of EAE in a clinically relevant murine model of multiple sclerosis. This study indicates that the agonistic Ab against 4-1BB can potentially be used as a novel immunotherapeutic agent for treating autoimmune diseases.

Diagnostic value of CDX-2 and TTF-1 expressions in separating metastatic neuroendocrine neoplasms of unknown origin.

Histomorphologic features and routine endocrine immunohistochemical (IHC) markers do not differentiate neuroendocrine tumors (NETs) in relation to their location, making it difficult to establish the site of origin of a metastatic neoplasm. Site-specific markers would be useful, particularly when examining small biopsies. CDX-2 and thyroid transcription factor-1 (TTF-1) are transcription factors that have been recently proposed as IHC markers of intestinal and pulmonary adenocarcinomas, respectively. However, their expression in NETs has not been widely studied. The objective of this study is to evaluate the expression of TTF-1 and CDX-2 in NETs and their potential usefulness in distinguishing gastrointestinal and pulmonary NETs from other sites. We performed an IHC study on formalin-fixed, paraffin-embedded sections from 155 primary NETs, including 60 pulmonary, 60 gastrointestinal, 30 pancreatic, and 5 NETs from other sites. In addition, we evaluated 13 metastatic NETs, including 11 cases of gastrointestinal and 2 of pulmonary origin. In this study, CDX-2 was expressed in 28/60 (47%) of gastrointestinal NETs with the following results: 11/11 (100%) appendiceal, 12/14 (86%) small intestinal, 3/4 (75%) colonic, 2/11 (18%) rectal, and 0/20 (0%) gastric. TTF-1 was expressed in pulmonary carcinoid tumors in 13/30 (43%) and in 27/30 (90%) pulmonary small cell carcinomas. NETs of other origins (pancreas, skin, ovary, and thymus) were negative for both TTF-1 and CDX-2. Metastatic neuroendocrine neoplasms of intestinal origin were positive for CDX-2 and negative for TTF-1. In conclusion, CDX-2 expression is highly specific in identifying NETs of intestinal origin and TTF-1 expression is helpful in identifying NETs of pulmonary origin, which can be quite useful in the diagnosis of metastatic NETs of unknown origin.

Signal Via Lymphotoxin-βR on Bone Marrow Stromal Cells Is Required for an Early Checkpoint of NK Cell Development

NK cells play an important role in the immune system but the cellular and molecular requirements for their early development are poorly understood. Lymphotoxin-α (LTα)−/− and LTβR−/− mice show a severe systemic reduction of NK cells, which provides an excellent model to study NK cell development. In this study, we show that the bone marrow (BM) or fetal liver cells from LTα−/− or LTβR−/− mice efficiently develop into mature NK cells in the presence of stromal cells from wild-type mice but not from LTα−/− or LTβR−/− mice. Direct activation of LTβR-expressing BM stromal cells is shown to promote to early NK cell development in vitro. Furthermore, the blockade of the interaction between LT and LTβR in adult wild-type mice by administration of LTβR-Ig impairs the development of NK cells in vivo. Together, these results indicate that the signal via LTβR on BM stromal cells by membrane LT is an important pathway for early NK cell development.

Molecular analysis of multifocal papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) frequently presents as a multifocal process. To study the importance of separating independent primary (IP) from intrathyroid metastatic (ITM) PTC, we examined 19 molecular markers on 42 separate tumors from 18 multifocal PTC cases. In 12 of 18 (66.7%) cases, including 6 of 12 (50%) papillary microcarcinoma cases, the same or similar profile of loss of heterozygosities (LOH) and v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutation was demonstrated, indicating that they were from the same primary and represented ITM. Different profiles of LOHs and BRAF mutation were detected in separate tumors of 6 of 18 cases, indicating that they represented IP. Patients with ITM, including papillary microcarcinoma, had significantly increased lymph node metastasis. The frequencies of LOHs of 17q21, 17p13, 10q23, and 22q13 were higher in tumors with lymph node metastasis, suggesting that these LOHs may be important in increased lymph node metastasis. LOH of 9p21 was found at the highest frequency in PTC (53.8%), followed by 1p36 (46.2%), 10q23 (34.6%), and 22q13 (34.6%). Papillary microcarcinoma had acquired similar genomic mutations as conventional PTC, but higher frequencies of mutations of BRAF, 1p36, 18q, and 22q13 were found in the larger PTC, suggesting that they might play a role in the aggressiveness of PTC. Different profiles of mutations were observed in conventional, follicular variants, and diffuse sclerosing variant of PTC, which might influence the different morphological appearances and clinical courses. In conclusion, molecular analysis can separate multifocal IP PTC from ITM PTC, and may be more important than tumor size in predicting lymph node metastasis, aggressiveness, and prognosis of PTC.

TGF-β2 Reduces Demyelination, Virus Antigen Expression, and Macrophage Recruitment in a Viral Model of Multiple Sclerosis

TGF-β2 is a potent immunoregulatory mediator that influences B cell, T cell, and macrophage function. To test whether this cytokine alters pathology in a model of virus-induced demyelinating disease, we treated SJL/J mice with TGF-β2 either before or after infection with Theiler’s murine encephalomyelitis virus. Treatment continued three times weekly through day 35 postinfection. TGF-β2 administration resulted in significantly smaller lesions and fewer virus Ag-positive cells in the spinal cords of infected SJL/J mice. Mice treated with TGF-β2 had similar levels of virus-specific IgG as infected, control-treated mice. TGF-β2 administration significantly increased the level of non-virus-specific activated CTLs, but had no effect on virus-specific CTLs. TUNEL revealed a decrease in the number of apoptotic nuclei in the spinal cord white matter of mice treated in vivo with TGF-β2. Immunostaining with an Ab to F4/80 revealed that TGF-β2-treated mice had significantly fewer F4/80-positive cells in the white matter of the spinal cord as compared with infected control-treated mice. These data suggest that TGF-β2 may control virus-induced demyelination via an immunomodulatory mechanism that reduces macrophage infiltration.

Absence of Spontaneous Central Nervous System Remyelination in Class II-deficient Mice Infected with Theiler's Virus

We previously showed that Theilers murine encephalomyelitis virus (TMEV)-infected major histocompatibility complex (MHC) class II-deficient mice develop both demyelination and neurologic deficits, whereas MHC class I-deficient mice develop demyelination but no neurologic deficits. The absence of neurologic deficits in the class I-deficient mice was associated with preserved sodium channel densities in demyelinated lesions, a relative preservation of axons, and extensive spontaneous remyelination. In this study, we investigated whether TMEV-infected class II-deficient mice, which have an identical genetic background (C57BL/6 x 129) as the class I-deficient mice, have preserved axons and spontaneous myelin repair following chronic TMEV-infection. Both class I- and class II-deficient mice showed similar extents of demyelination of the spinal cord white matter 4 months after TMEV infection. However, the class I-deficient mice demonstrated remyelination by oligodendrocytes, whereas class II-deficient mice showed minimal if any myelin repair. Demyelinated lesions, characterized by inflammatory infiltrates in both mutants, revealed disruption of axons in class II- but not class I-deficient mice. Further characterization revealed that even though class II-deficient mice lacked TMEV-specific IgG, they had virus-specific IgM, which, however, did not neutralize TMEV in vitro. In addition, class II-deficient mice developed TMEV-specific cytotoxic T-lymphocytes in the CNS during the acute (7 days) disease, but these cytotoxic lymphocytes were not present in the chronic stage of disease, despite a high titer of infectious virus throughout the disease. We envision that the presence of demyelination, high virus titer, absence of remyelination, and axonal disruption in chronically infected class II-deficient mice contributes to the development of paralytic disease.

Diagnostic and prognostic utility of molecular markers in synchronous bilateral breast carcinoma

Histologic criteria have a limited role in determining whether the synchronous bilateral breast carcinomas represent two primaries or a metastasis to the contralateral breast. We studied the molecular analysis of synchronous bilateral breast carcinoma and whether they are originating from a single or different clone. We examined 17 patients with breast carcinoma, including 12 patients with synchronous bilateral carcinomas and control group of 5 infiltrating ductal carcinomas with regional lymph node metastases. Mutations were quantitatively determined to detect loss of heterozygosity (LOH) and microsatellite size alterations for a broad panel of 15 markers, involving 10 chromosomes using polymerase chain reaction. The carcinomas were classified as de novo or metastasis based on three levels of concordance: (1) marker-affected tumors were considered concordant if 50% or more of the same markers were mutated, (2) same gene copy affected, and (3) temporal sequence of mutation acquisition. In synchronous bilateral breast carcinoma patients, molecular analysis showed discordant mutations in all cases, supporting the diagnosis of de novo bilateral primary breast carcinomas. In patients with lymph node metastases, the primary breast carcinoma and metastases shared the same mutations, revealing a metastatic lesion. In conclusion, the application of molecular technology may play an important role for the differential diagnosis of dual primary carcinomas vs a metastatic breast cancer to contralateral breast. In this study, synchronous bilateral breast cancers represent two independent primaries rather than metastatic events.

Thyroid Bethesda reporting category, 'suspicious for papillary thyroid carcinoma', pitfalls and clues to optimize the use of this category.

A. Mahajan, X. Lin and R. Nayar

Mucinous nonneoplastic cyst of the pancreas: apomucin phenotype distinguishes this entity from intraductal papillary mucinous neoplasm.

Mucinous nonneoplastic cyst of the pancreas is a newly described and rare cystic lesion with unknown histogenesis. It is defined as a cystic lesion lined with mucinous epithelium, supported by hypocellular stroma and not communicating with the pancreatic ducts. It is very challenging to differentiate this lesion from other cystic mucinous neoplasms of the pancreas such as branch-duct intraductal papillary mucinous neoplasm by morphology. In this study, a total of 436 pancreatic specimens resected between 2002 and 2007 in our institution were reviewed. Fifteen (3.4%, 15/436) mucinous nonneoplastic cysts were identified. They included 3 males and 12 females, with a median age of 60 years. Forty-six percent of cases (7/15) occurred in pancreatic head, 27% (4/15) in neck, 7% (1/15) in body, and 20% (3/15) in tail. The size of lesions ranged from 0.5 to 3.5 cm in greatest dimension. In most cases (12/15, 80%), mucinous nonneoplastic cyst was associated or adjacent to acinar-ductal mucinous metaplasia. These morphologic data indicate that mucinous nonneoplastic cyst is not really a rare disease and may originate from acinar-duct mucinous metaplasia histogenestically. Furthermore, apomucin immunostains of mucinous nonneoplastic cyst showed MUC1 expressed in 27% (4/15) cases, MUC5AC in 67% (10/15 cases), and MUC2 was were negative in all cases, whereas intraductal papillary mucinous neoplasm (n = 17; 5 main duct type, 12 branch-duct type) showed focal and weak MUC1 positivity in 18% (3/17) cases, MUC2 positivity in 71% (12/17) cases, and all intraductal papillary mucinous neoplasm (17/17) were MUC5AC positive. The clonality assay with the HUMARA gene revealed that the mucinous nonneoplastic cysts were of polyclonal origin. For the first time, using HUMARA assay, we demonstrate the nonneoplastic nature of these cysts and further characterize morphologic and immunophenotypic properties that allow differentiation from intraductal papillary mucinous neooplasm.

Transgenic Expression of Theiler's Murine Encephalomyelitis Virus Genes in H-2b Mice Inhibits Resistance to Virus-Induced Demyelination

ABSTRACT We investigated the role of the immune system in protecting against virus-induced demyelination by generating lines of transgenic B10 (H-2b ) congenic mice expressing three independent contiguous coding regions of the Theilers murine encephalomyelitis virus (TMEV) under the control of a class I major histocompatibility complex (MHC) promoter. TMEV infection of normally resistant B10 mice results in virus clearance and development of inflammatory demyelination in the spinal cord. Transgenic expression of the viral capsid genes resulted in inactivation of virus-specific CD8+ T lymphocytes (class I MHC immune function) directed against the relevant peptides, but it did not affect production of virus capsid-specific antibodies or lymphocyte proliferation to the virus antigen (class II MHC immune functions). Following intracerebral infection with TMEV, all three lines of mice survived the acute encephalitis but transgenic mice expressing VP1 (or the cluster of virus capsid proteins [VP4, VP2, and VP3] mapping to the left of VP1 in the TMEV genome) developed virus persistence and subsequent demyelination in spinal cord white matter. Transgenic mice expressing noncapsid proteins mapping to the right of VP1 (2A, 2B, 2C, 3A, 3B, 3C, and 3D) cleared the virus and did not develop demyelination. These results are consistent with the hypothesis that virus capsid gene products of TMEV stimulate class I-restricted CD8+ T-cell immune responses, which are important for virus clearance and for protection against myelin destruction. Presented within the context of self-antigens, inactivation of these cells by ubiquitous expression of relevant virus capsid peptides partially inhibited resistance to virus-induced demyelination.