Naoki Kurita

Enhanced humoral immune responses against T-independent antigens in Fcα/μR-deficient mice

IgM is an antibody class common to all vertebrates that plays a primary role in host defenses against infection. Binding of IgM with an antigen initiates the complement cascade, accelerating cellular and humoral immune responses. However, the functional role of the Fc receptor for IgM in such immune responses remains obscure. Here we show that mice deficient in Fcα/μR, an Fc receptor for IgM expressed on B cells and follicular dendritic cells (FDCs), have enhanced germinal center formation and affinity maturation and memory induction of IgG3+ B cells after immunization with T-independent (TI) antigens. Moreover, Fcα/μR-deficient mice show prolonged antigen retention by marginal zone B (MZB) cells and FDCs. In vitro studies demonstrate that interaction of the IgM immune complex with Fcα/μR partly suppress TI antigen retention by MZB cells. We further show that downregulation of complement receptor (CR)1 and CR2 or complement deprivation by in vivo injection with anti-CR1/2 antibody or cobra venom factor attenuates antigen retention by MZB cells and germinal center formation after immunization with TI antigens in Fcα/μR−/− mice. Taken together, these results suggest that Fcα/μR negatively regulates TI antigen retention by MZB cells and FDCs, leading to suppression of humoral immune responses against T-independent antigens.

Caspase-Independent Cell Death by CD300LF (MAIR-V), an Inhibitory Immunoglobulin-Like Receptor on Myeloid Cells

The myeloid-associated Ig-like receptor family (CD300) consists of nine activating or inhibitory cell surface receptors preferentially expressed on myeloid cells and are encoded by the genes in a small cluster on mouse chromosome 11. One of the receptors, CD300LF (MAIR-V), has a long cytoplasmic tail containing two consensus ITIMs and an immunoreceptor tyrosine-based switching motif, suggesting that CD300LF regulates the activation of myeloid cells. However, the functional characteristics of this receptor are still incompletely understood. In this study, we demonstrate that cross-linking CD300LF with anti-CD300LF mAb induced cell death in peritoneal macrophages as well as in several transfectants expressing CD300LF. CD300LF-mediated cell death was dependent on the cytoplasmic region but did not require an ITIM or immunoreceptor tyrosine-based switching motif. Scanning electron microscopy revealed a loss of blebs from the surface of the dead cells mediated by CD300LF, a morphological feature similar to that observed in apoptotic cells. However, CD300LF-mediated cell death was not inhibited by a caspase inhibitor, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, or autophagy inhibitors, 3-methyladenine or N-acetyl-l-cystein. Moreover, the splicing isoform of a transcription factor, X-box binding protein-1, which is produced in dead cells as a response to endoplasmic reticulum stress, was not detected. Together, these results indicate that CD300LF mediates caspase and endoplasmic reticulum stress-independent cell death by a novel mechanism.

The immunoreceptor adapter protein DAP12 suppresses B lymphocyte–driven adaptive immune responses

Human and mouse B cells lacking functional DAP12 are hyperresponsive, and DAP12 works with MAIR-II (CD300d) to negatively regulate B cell activity.

Identification of the Fcα/μR isoform specifically expressed in the kidney tubules

Fcalpha/muR is expressed not only in lymphoid, but also in non-lymphoid organs, including kidney. However, molecular and functional characteristics of Fcalpha/muR, particularly expressed in non-lymphoid organs, have remained unclear. Here we identified an isoform of Fcalpha/muR in the murine kidney on the C57BL/6J background. The kidney expressed only the isoform, which was not expressed in other lymphoid and non-lymphoid organs, and this isoform binds both IgA and IgM. Immunohistochemical analyses suggested that the Fcalpha/muR isoform was expressed in the tubular epithelial cells, but not in the glomeruli. This was confirmed by flow cytometry analysis of isolated tubular epithelial cells and by RT-PCR analyses using the separately excised glomerular and tubular regions by the laser microdissection system. These results suggest that Fcalpha/muR may not be involved in IgA deposition in glomerular mesangium cells in IgA nephropathy. Rather, it may play an important role in immunity in the renal tubular regions.

Detection of the G17V RHOA mutation in angioimmunoblastic T-cell lymphoma and related lymphomas using quantitative allele-specific PCR.

Angioimmunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) are subtypes of T-cell lymphoma. Due to low tumor cell content and substantial reactive cell infiltration, these lymphomas are sometimes mistaken for other types of lymphomas or even non-neoplastic diseases. In addition, a significant proportion of PTCL-NOS cases reportedly exhibit features of AITL (AITL-like PTCL-NOS). Thus disagreement is common in distinguishing between AITL and PTCL-NOS. Using whole-exome and subsequent targeted sequencing, we recently identified G17V RHOA mutations in 60–70% of AITL and AITL-like PTCL-NOS cases but not in other hematologic cancers, including other T-cell malignancies. Here, we establish a sensitive detection method for the G17V RHOA mutation using a quantitative allele-specific polymerase chain reaction (qAS-PCR) assay. Mutated allele frequencies deduced from this approach were highly correlated with those determined by deep sequencing. This method could serve as a novel diagnostic tool for 60–70% of AITL and AITL-like PTCL-NOS.

Aprepitant does not alter prednisolone pharmacokinetics in patients treated with R-CHOP

Aprepitant, a neurokinin 1 receptor antagonist, is an effective antiemetic drug in the prevention of chemotherapy-induced nausea and vomiting. Aprepitant co-administration increases plasma concentrations of dexamethasone and methylprednisolone by inhibiting cytochrome P450 (CYP) 3A4 [1], whereas pharmacokinetics of cyclophosphamide, which is also metabolized by CYP enzymes including CYP3A4, is not significantly changed by aprepitant [2]. Thus, aprepitant co-administration provides different effects on pharmacokinetics of CYP substrates; however, it is unknown whether aprepitant affects pharmacokinetics of prednisolone, another CYP3A4 substrate. We aimed to evaluate the effect of aprepitant on pharmacokinetics of prednisolone, and the safety and efficacy of aprepitant when administered together with rituximab, cyclophosphamide (Shionogi, Osaka, Japan), doxorubicin (Adriamycin) (Sandoz, Tokyo, Japan), vincristine (Nippon Kayaku, Tokyo, Japan), and prednisolone (R-CHOP) in patients with non-Hodgkin’s lymphoma. We conducted a nonrandomized, open-label, single-group before/after design study between courses 1 and 2 of R-CHOP. This study was approved by the institutional review board of the University of Tsukuba Hospital. Patients received 100 mg of oral prednisolone from days 1–5 in divided doses of 60 mg at 8 am and 40 mg at 1 pm. Aprepitant was added orally for 3 days (125 mg on day 1, and 80 mg on days 2 and 3) at 7 am during the course 2. In each course, 3 mg of granisetron was given twice on day 1. Ten patients (diffuse large B-cell lymphoma in seven and follicular lymphoma in three) completed the study. Antiemetic CR (defined as no emetic episodes and no use of rescue medication) without and with aprepitant was observed in 8 and 10 out of 10 patients, respectively. A series of serum prednisolone concentrations in eight patients were measured. The mean AUC of prednisolone from 0 to 5 h was not different between the courses 1 and 2 (2200 ± 490 and 2178 ± 794 ng h/ml, respectively; P = 0.932) (Figure 1), although areas under the curve of prednisolone were increased in four patients and decreased in other four patients by the co-administration of aprepitant. The median (range) Tmax [2 (0.5–2) and 2 (0.5–5) h, respectively] and the mean Cmax (646 ± 191 and 634 ± 285 ng/ml, respectively; P = 0.88) were not affected by aprepitant. There was no significant difference in blood glucose concentration and blood pressure level between the courses 1 and 2. Previous studies have shown that CYP3A4 inhibitors, such as ketoconazole and itraconazole, do not affect the metabolism of prednisolone [3, 4], whereas they increase plasma concentration of dexamethasone and methylprednisolone [1]. Consistent with these reports, our results indicated that aprepitant had virtually no impact on prednisolone pharmacokinetics. Hepatic metabolism for prednisolone is different from those for dexamethasone and methylprednisolone, in that 11-β-hydroxysteroid dehydrogenase plays a role in addition to CYP3A4 only for prednisolone, through the conversion of the hydroxyl group to ketone on the 11th position of C-ring. Therefore, the contribution of CYP3A4 to the metabolism may be lower in prednisolone than in dexamethasone and methylprednisolone [5]. We concluded that aprepitant could be safely administered when strengthened antiemetic treatment is required, without serious drug interactions with prednisolone in R-CHOP.

Early Pathologic Findings of Bronchiolitis Obliterans after Allogeneic Hematopoietic Stem Cell Transplantation: A Proposal from a Case

Bronchiolitis obliterans (BO) is one of the serious, noninfectious pulmonary complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Early diagnosis of BO is usually difficult because patients are often asymptomatic at an initial stage of the disease and pathologic findings are available mostly at the late stages. Therefore, the diagnosis of the disease is based on the pulmonary function test using the National Institute of Health consensus criteria. Here, we report a case of slowly progressive BO. A biopsy specimen at an early stage demonstrated alveolar destruction with lymphocyte infiltration in bronchial walls and mild narrowing of bronchioles without fibrosis, those were strongly indicative of initial pathologic changes of BO. Definitive BO followed, which was proven by both clinical course and autopsy. While alloreactive lymphocytes associated with chronic graft-versus-host disease are believed to initiate BO, we present a rare case that directly implies such a scenario.

Prognosis Factors in Japanese Elderly Patients with Primary Central Nervous System Lymphoma Treated with a Nonradiation, Intermediate-Dose Methotrexate-Containing Regimen

Background: Nearly half of all patients with primary central nervous system lymphoma (PCNSL) are known to be aged over 60 years. However, clinical factors affecting treatment outcomes in elderly patients are understudied. Methods: We analyzed 38 patients with PCNSL older than 60 years. All patients were treated with a nonradiation, intermediate-dose methotrexate-containing regimen between March 2005 and May 2013 at the University of Tsukuba Hospital. Results: The 3-year overall survival and progression-free survival rates were 56.2% (95% confidence interval (CI) 36.2-76.2%) and 29.8% (95% CI 9-50.6%), respectively, with a median follow-up of 36.5 months. We found that an age > 75 years, a Karnofsky performance score < 70, altered mentation, and a creatinine clearance (CrCl) > 90 ml/min were significant (p < 0.05) factors associated with a worse survival, by univariate analysis. Multivariate analysis revealed that CrCl (p < 0.05; hazard ratio (HR) = 3.39; 95% CI 1.08-10.68) and altered mentation (p < 0.05; HR = 6.27; 95%CI 1.37-28.83) were independent significant association factors. The most frequent adverse event was myelosuppression, with grade 3-4 hematologic toxicities in 28 patients. No delayed neurotoxicities were observed. Conclusion: More intensive therapy may be introduced in selected patients with poor prognosis factors to improve outcomes.

Retrospective assessment of secondary prophylaxis for invasive aspergillosis in neutropenic hematology patients and identification of risk factors for relapse of fungal disease

Abstract Background: Invasive aspergillosis (IA) is a critical complication in neutropenic patients. Recurrent IA is especially associated with high mortality. Therefore, secondary prophylaxis is important in patients with a history of IA. We retrospectively assessed the effect of secondary prophylaxis for IA. Methods: We reviewed the medical records of 46 hematology patients who developed possible, probable, or proven IA according to the EORTC/MSG criteria between 2005 and 2009, and who subsequently underwent chemotherapy (n = 30) or stem cell transplantation (n = 16). Results: Ten patients developed recurrent IA within 10 days after recovery from neutropenia. None of the 15 patients who achieved complete response (CR) of IA experienced recurrent IA. Among patients who did not achieve CR of IA, multivariate analysis identified the following independent risk factors: female sex (hazard ratio (HR) 7.23, 95% confidence interval (CI) 2.38–21.9, p = 0.00047), high serum C-reactive protein level (≥ 1 mg/dl) at the beginning of subsequent therapy (HR 4.46, 95% CI 1.51–13.2, p = 0.007), and the use of micafungin (HR 12.0, 95% CI 2.03–71.2, p = 0.0061) or amphotericin B (HR 16.5, 95% CI 1.56–174, p = 0.020) for secondary prophylaxis (reference: voriconazole). Conclusions: Three risk factors for recurrent IA were identified. However, a prospective controlled trial is required to evaluate the impact of secondary prophylactic regimens.

Complete Remission in Systemic Skin Interdigitating Dendritic Cell Sarcoma after ABVD Chemotherapy

Interdigitating dendritic cell sarcoma (IDCS) is a rare and aggressive neoplasm that is thought to arise from dendritic cells. This disease usually involves the lymph nodes and, rarely, extra-nodal sites. We report a 62-year-old man presenting skin nodules in the head, body, and extremities, as well as bone marrow involvement. Morphologic analysis of a biopsied specimen from the skin lesion was consistent with IDCS. Immunohistochemical staining demonstrated that the tumor cells were positive for IDCS-associated antigens such as CD4, CD45, CD68 (KP-1), and S-100 protein. Complete remission was achieved by treatment with 6 cycles of ABVD (adriamycin, bleomycin, vinblastine, and dacarbazine) chemotherapy. Although the optimal treatment of IDSC remains unknown, the experience in the current case supports the notion that ABVD chemotherapy may be effective for IDCS, and further extends this idea to rare patients presenting multiple skin lesions.