Yasuhisa Sakakibara

Clinical Significance of Cloned Expansion and CD5 Down-Regulation in Epstein-Barr Virus (EBV)- Infected CD8 + T Lymphocytes in EBV-Associated Hemophagocytic Lymphohistiocytosis

Epstein-Barr virus (EBV) is the pathogen that most commonly triggers infection-associated hemophagocytic lymphohistiocytosis (HLH) and ectopically infects CD8(+) T cells in EBV-associated HLH (EBV-HLH). We recently described an EBV-HLH patient who had a clonally expanded population of EBV-infected CD8(+) T cells with CD5 down-regulation. To determine whether this finding could serve as a useful marker for EBV-HLH, we investigated 5 additional patients. We found a significant increase in the subpopulation of CD8(+) T cells with CD5 down-regulation and bright human leukocyte antigen (HLA)-DR expression in all patients with EBV-HLH but not in patients with infectious mononucleosis or in control subjects. Such T cells were frequently found to be larger cells that stained positive for a specific T cell receptor VB. We also demonstrated that those cells were the major cellular target of EBV, and their numbers progressively declined in parallel with the serum ferritin levels. All together, our findings reveal the immunophenotypic characteristics of EBV-infected CD8(+) T cells and may provide a valuable tool for the diagnosis of EBV-HLH.

Distinct cytokine profile in juvenile systemic lupus erythematosus-associated macrophage activation syndrome

Macrophage activation syndrome (MAS) has been observed in patients with systemic lupus erythematosus (SLE). Recognition of MAS in patients with SLE may be particularly challenging because it may mimic the clinical features of the underlying disease or be confused with an infectious complication. Massive hypercytokinemia is strongly associated with the pathogenesis of systemic lupus erythematosus-associated macrophage activation syndrome (SLE-MAS) but the pathogenesis and kinetics of cytokine release in SLE-MAS patients is not well studied. We present a case of SLE-MAS. The patient showed the distinct cytokine profile of SLE-MAS compared to systemic juvenile idiopathic arthritis associated MAS and Epstein-Barr virus-induced hemophagocytic lymphohistiocytosis. The observed TNF-α dominant increase appears to be characteristic of SLE-MAS. IgM type antilymphocyte antibody (ALAB) was detected on the surface of lymphocytes during the acute phase and disappeared when the patient was in remission. The patient had a heterozygous P369S-R408Q mutation in the MEFV gene. Our results suggest that ALAB and a MEFV mutation might play important roles in the pathogenesis of SLE-MAS. Furthermore, the cytokine profile of SLE-MAS differs from that of S-JIA-MAS: the TNF-α dominant increase appears to be characteristic.

Analysis of mutations and recombination activity in RAG-deficient patients.

Mutations in the recombination activating genes (RAG1 or RAG2) can lead to a variety of immunodeficiencies. Herein, we report 5 cases of RAG deficiency from 5 families: 3 of Omenn syndrome, 1 of severe combined immunodeficiency, and 1 of combined immunodeficiency with oligoclonal TCRγδ(+) T cells, autoimmunity and cytomegalovirus infection. The genetic defects were heterogeneous and included 6 novel RAG mutations. All missense mutations except for Met443Ile in RAG2 were located in active core regions of RAG1 or RAG2. V(D)J recombination activity of each mutant was variable, ranging from half of the wild type activity to none, however, a significant decrease in average recombination activity was demonstrated in each patient. The reduced recombination activity of Met443Ile in RAG2 may suggest a crucial role of the non-core region of RAG2 in V(D)J recombination. These findings suggest that functional evaluation together with molecular analysis contributes to our broader understanding of RAG deficiency.

Down-regulation of CD5 expression on activated CD8+ T cells in familial hemophagocytic lymphohistiocytosis with perforin gene mutations

Hemophagocytic lymphohistiocytosis (HLH) is characterized by uncontrolled activation of T cells and macrophages with overproduction of cytokines. Familial HLH type 2 (FHL2) is the most common form of primary HLH and is caused by mutations in PRF1. We have recently described a significant increase in the subpopulation of CD8(+) T cells with clonal expansion and CD5 down-regulation in Epstein-Barr virus associated-HLH, which represented a valuable tool for its diagnosis. However, this unusual phenotype of CD8(+) T cells has not been investigated fully in patients with FHL2. We performed immunophenotypic analysis of peripheral blood and measured serum pro-inflammatory cytokines in five patients with FHL2. All patients showed significantly increased subpopulations of activated CD8(+) T cells with down-regulation of CD5, which were negligible among normal controls. Analysis of T-cell receptor Vβ repertoire suggested the reactive and oligoclonal expansion of these cells. The proportion of the subset declined after successful treatment concomitant with reduction in the serum levels of cytokines in all patients except one who continued to have a high proportion of the subset and died. These findings suggest that down-regulation of CD5 on activated CD8(+) T cells may serve as a useful marker of dysregulated T cell activation and proliferation in FHL2.

Sequentially appearing erythema nodosum, erythema multiforme and Henoch-Schönlein purpura in a patient with Mycoplasma pneumoniae infection: a case report.

IntroductionA wide variety of skin manifestations are associated with Mycoplasma pneumoniae infection. However, the precise mechanisms by which M. pneumoniae infection is able to produce a variety of cutaneous manifestations are poorly understood.Case presentationAn 8-year-old Japanese girl presented with sequential skin manifestations, including erythema nodosum, erythema multiforme and Henoch-Schönlein purpura. Although a chest radiograph showed no significant lung abnormalities, serological examinations revealed that these skin manifestations were associated with M. pneumoniae infection.ConclusionIt has been reported that the variations in cutaneous manifestations of M. pneumoniae infection can be attributed to the immaturity of the adaptive immunity of a host. However, the case presented herein indicates that skin manifestations might not be specific for each individual. An awareness of the varied patterns of cutaneous disease is essential for the early diagnosis and treatment of patients with manifestations of M. pneumoniae infection.

Clonal expansion of Epstein-Barr virus (EBV)-infected γδ T cells in patients with chronic active EBV disease and hydroa vacciniforme-like eruptions

Chronic active Epstein–Barr virus (EBV) disease (CAEBV) is a systemic EBV-positive lymphoproliferative disorder characterized by fever, lymphadenopathy, and splenomegaly. Patients with CAEBV may present with cutaneous symptoms, including hypersensitivity to mosquito bites and hydroa vacciniforme (HV)-like eruptions. HV is a rare photodermatosis characterized by vesicles and crust formation after exposure to sunlight, with onset in childhood, and is associated with latent EBV infection. While γδ T cells have recently been demonstrated to be the major EBV-infected cell population in HV, the immunophenotypic features of EBV-infected γδ T cells in CAEBV with HV-like eruptions or HV remain largely undetermined. We describe three patients with CAEBV whose γδ T cells were found to be the major cellular target of EBV. HV-like eruptions were observed in two of these patients. A clonally expanded subpopulation of γδ T cells that were highly activated and T cell receptor Vγ9- and Vδ2-positive cells was demonstrated in all patients. We also show that the clonally expanded γδ T cells infiltrated into the HV-like eruptions in one patient from whom skin biopsy specimens were available. These results suggest the pathogenic roles of clonally expanded γδ T cells infected by EBV in patients with CAEBV and HV-like eruptions.

Enhanced exon 2 skipping caused by c.910G>A variant and alternative splicing of MEFV genes in two independent cases of familial Mediterranean fever

Most reported cases of familial Mediterranean fever (FMF) involve missense mutations of MEFV concentrated within exon 10. We experienced two independent pedigrees of a unique variant in the MEFV gene that might cause excessive exon 2 skipping due to enhanced alternative splicing. In this study, we tried to elucidate the molecular mechanism of the MEFV variant as a cause of the FMF phenotype. Peripheral blood was obtained from volunteers and two patients with homozygous c.910G>A variant of the MEFV gene. MEFV messenger RNA (mRNA) expression patterns in mononuclear cells and granulocytes were compared using forward and reverse primers from exons 1 and 3, respectively. Expression profiles of pyrin were examined by transfecting wild-type and variant MEFV genes into HEK293T cells. Expression of normal-sized mRNA was extremely reduced in these patients, whereas that of aberrant short mRNA, deleting exon 2 (Δex2), was significantly increased. Immunohistochemical and immunoblotting analyses revealed a truncated immunoreactive pyrin protein in cells transfected with Δex2 cDNA. The MEFV gene c.910G>A variant results in accelerated aberrant splicing with abnormal protein size, presumably leading to anomalous pyrin function. This is the first report to show that an MEFV variant other than missense mutation is responsible for the FMF phenotype.

Flow cytometric analysis of skin blister fluid induced by mosquito bites in a patient with chronic active Epstein-Barr virus infection

In chronic active Epstein–Barr virus (EBV) infection (CAEBV), ectopic EBV infection has been described in T or natural killer (NK) cells. NK cell-type infection (NK-CAEBV) is characterized by large granular lymphocytosis, high IgE levels and unusual reactions to mosquito bites, including severe local skin reactions, fever and liver dysfunction. However, the mechanisms underlying these reactions remain undetermined. Herein, we describe a patient with NK-CAEBV whose blister fluid after mosquito bites was analyzed. The patient exhibited significant increases in the percentage of CD56+ NK cells in the fluid compared with a simple mosquito allergy, in which the majority of infiltrated cells were CD203c+ cells, indicating basophils and/or mast cells. His fluid also contained CD203c+ cells, and his circulating basophils were activated by mosquito extracts in vitro. These results suggest that CD203c+ cells as well as NK cells may play pathogenic roles in the severe skin reactions to mosquito bites in NK-CAEBV.

Basophil activation by mosquito extracts in patients with hypersensitivity to mosquito bites

Hypersensitivity to mosquito bites (HMB) is a cutaneous disorder belonging to the group of Epstein–Barr virus (EBV)‐associated T/natural killer (NK)‐cell lymphoproliferative diseases, and is primarily mediated by EBV‐infected NK cells. It is characterized by intense local skin reactions accompanied by general symptoms after mosquito bites, and infiltration of EBV‐infected NK cells into the bite sites. However, the mechanisms underlying these reactions have not been fully examined. We recently described the activation of circulating basophils by mosquito extracts in vitro in a patient with HMB. To further investigate this finding, we studied four additional patients with HMB. All patients showed typical clinical features of HMB after mosquito bites and they had NK lymphocytosis and high peripheral blood EBV DNA loads. We found evidence of EBV infection in NK cells through in situ hybridization that detected EBV‐encoded small RNA‐1, and flow cytometry showed HLA‐DR expression on almost all NK cells. Basophil activation tests with the extracts of epidemic mosquitoes Culex pipiens pallens and Aedes albopictus showed positive responses to one or both extracts in all samples from patients with HMB, suggesting the presence of mosquito antigen‐specific IgE and its binding to basophils. In particular, the extract of Aedes albopictus was able to activate basophils in all available patient samples. These results indicate that basophils and/or mast cells activated by mosquito bites may be involved in initiation and development of severe skin reactions to mosquito bites in HMB.

Agranulocytosis after infectious mononucleosis

We report the case of a 5-year-old boy with agranulocytosis after infectious mononucleosis (IM). Antibodies against anti-human neutrophil-specific antigens (HNA)-1 were detected in his serum. A literature review on agranulocytosis after IM and our case suggest that anti-HNA-1 antibodies play important roles in agranulocytosis associated with IM.