Sho Hokibara

CD27: a memory B-cell marker

Abstract Memory B cells generate immunoglobulins rapidly and vigorously in the secondary immune response. Here, Kazunaga Agematsu and colleagues highlight studies confirming that CD27 is a memory B-cell marker.

Absence of IgD-CD27(+) memory B cell population in X-linked hyper-IgM syndrome.

The present study analyzed peripheral blood B cell populations separated by IgD and CD27 expression in six males with X-linked hyper-IgM syndrome (XHIM). Costimulation of mononuclear cells from most of the patients induced no to low levels of class switching from IgM to IgG and IgA with Staphylococcus aureus Cowan strain (SAC) plus IL-2 or anti-CD40 mAb (anti-CD40) plus IL-10. Measurable levels of IgE were secreted in some of the patients after stimulation with anti-CD40 plus IL-4. Costimulation with SAC plus IL-2 plus anti-CD40 plus IL-10 yielded secretion of significant levels of IgG in addition to IgM, but not IgA. The most striking finding was that peripheral blood B cells from all of the six patients were composed of only IgD+ CD27(-) and IgD+ CD27(+) B cells; IgD- CD27(+) memory B cells were greatly decreased. IgD+ CD27(+) B cells from an XHIM patient produced IgM predominantly. Our data indicate that the low response of IgG production in XHIM patients is due to reduced numbers of IgD- CD27(+) memory B cells. However, the IgG production can be induced by stimulation of immunoglobulin receptors and CD40 in cooperation with such cytokines as IL-2 and IL-10 in vitro.

Theophylline induces neutrophil apoptosis through adenosine A2A receptor antagonism.

This study was designed to determine whether theophylline would augment granulocyte apoptosis via a mechanism of adenosine A2A receptor antagonism. A selective adenosine A2 receptor agonist (CGS‐21680, 1 μM) exhibited the most efficient potency for decreasing neutrophil apoptosis for 16 h from 63 ± 5 to 19 ± 4% (P < 0.001); it exerted poor and adverse effects on eosinophil survival. A selective protein kinase A inhibitor KT‐5720 (10 μM) reversed the capacity of dibu‐tyryl cAMP but not CGS‐21680 to induce an inhibitory effect on neutrophil apoptosis, suggesting that occupancy of adenosine A2 receptors inhibit neutrophil apoptosis by a cAMP‐independent mechanism. Theophylline derivatives show the following pattern of potency for inducing neutrophil apoptosis competing with CGS‐21680: 8‐phenyltheophylline = 8‐p‐sulfophenyltheophylline > theophylline ≫ enprofylline. This pattern is consistent with the affinity established for A2A receptors. Theophylline demonstrated an additive effect to that of anti‐Fas antibody (CH11, 1 μg/mL) in inducing neutrophil apoptosis, but not to that of adenosine deaminase or KF‐17837 (a selective A2 receptor antagonist; 1 μM), suggesting conflicting effects on the receptor antagonism. These findings suggest that theophylline has an immunomodulatory action on neutrophil apoptosis via a mechanism of A2A antagonism. J. Leukoc. Biol. 67:529–535; 2000.

Plasma Cell Generation from B-Lymphocytes via CD27/CD70 Interaction

To produce antibodies, the differentiation of B cells into antibody-secreting cells, plasma cells, is required. We describe that ligation of CD27, which belongs to the tumor necrosis factor receptor (TNFR) family and is a memory marker of B cells, yields crucial signals that positively control the entry of B cells into the pathway to plasma cells. The triggering via CD27 by CD27 ligand (CD70) on purified peripheral blood B cells yielded an increase in the number of plasma cells in the presence of interleukin-10 (IL-10). The differentiation into plasma cells by a combination of IL-10 and CD70-transfectants occurred in CD27+ B cells, but not in CD27- B cells. Moreover, the addition of IL-2 to the IL-10 and CD70-transfectants greatly induced the differentiation into plasma cells. In the presence of only IL-2, IL-4 or IL-6, CD70-transfectants did not promote the differentiation into plasma cells. On the other hand, CD40 signaling increased the expansion of a B cell pool from peripheral blood B cells primarily activated by IL-2, IL-10 and anti-CD40 mAb. These data demonstrate that CD27 ligand (CD70) is a key molecule to direct the differentiation of CD27+ memory B cells toward plasma cells in cooperation with IL-10.

Marked eosinophilia in interleukin-5 transgenic mice fails to prevent Trichinella spiralis infection.

In order to study the role of eosinophils in the host defense against Trichinella spiralis infection, worm recovery after infection with T. spiralis was compared between interleukin-5 transgenic (IL-5 Tg) mice with a constant high level of peripheral eosinophils and nontransgenic C3H/HeN mice. No significant difference in the recovery of muscle larvae or adult worms in the small intestine, fecundity of female adult worms, or infectivity of newborn larvae was observed between nonimmunized C3H/HeN and IL-5 Tg mice or C3H/HeN and IL-5 Tg mice immunized with somatic antigen of T. spiralis. However, a significant difference was observed in the fecundity of female adult worms and recovery of muscle larvae between nonimmunized and immunized IL-5 Tg mice or C3H/HeN mice. These results demonstrate that having more eosinophils does not improve immunity against the various aspects of T. spiralis infection.

Effects of monoclonal antibodies to adhesion molecules on eosinophilic myocarditis in Toxocara canis-infected CBA/J mice

Eosinophilic myocarditis followed by fibrosis of the cardiac muscle was observed in addition to peripheral blood eosinophilia in CBA/J mice infected with Toxocara canis. The infected mice were used as an experimental model of eosinophilic endomyocarditis associated with hypereosinophilic syndrome. Effects of in vivo treatment with MoAbs to adhesion molecules on eosinophilic myocarditis were examined using this experimental model. Expressions of intercellular adhesion molecule‐1 (ICAM‐1) and vascular cell adhesion molecule‐1 (VCAM‐1) on endothelial cells of capillaries in myocardium were increased 1 and 2 weeks after infection. Infiltration of very late antigen (VLA)‐4+ and/or CD11a+ cells into the cardiac muscles was also observed 1 and 2 weeks after infection. Infiltration of eosinophils into the heart was significantly suppressed by anti‐CD18 MoAb and anti‐VLA‐4 MoAb, and focal fibrosis of the cardiac muscle was also significantly suppressed by combined administration of anti‐CD18 and anti‐ICAM‐1 MoAbs. These results indicate that adhesion molecules may play important roles in eosinophilic myocarditis, and that blockade of interaction between adhesion molecules and their ligands may help to control it.

Markedly elevated CD64 expressions on neutrophils and monocytes are useful for diagnosis of periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome during flares

Periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome is the most commonly encountered autoinflammatory disease in children, but its pathogenesis and diagnostic biomarkers are unknown. In this study, we examined the utility of CD64, a member of the Fcγ receptors, expressions on neutrophils and monocytes in diagnosing patients with PFAPA, along with other autoinflammatory diseases exhibiting periodic fever, and bacterial infections. Although CD64 was expressed at a similar level in the attack-free period of PFAPA and in controls, CD64 expressions on both neutrophils and monocytes were dramatically increased during attacks. Serum IFN-γ also increased in some PFAPA patients during flares, suggesting the involvement of T cell activation. Our findings demonstrate that remarkable CD64 expression during PFAPA flares serves as a potential biomarker for the diagnosis. We also suspect that IFN-γ, possibly from retention of activated T cells in peripheral tissues, increases CD64 synthesis in such cases.

Increased CD45RO+ CD62L+ CD4+ T-cell subpopulation responsible for Th2 response in Kimura's disease.

Kimuras disease is characterized by subcutaneous masses, eosinophilia, and markedly elevated serum immunoglobulin E, suggesting that T helper (Th)2 cells may play a role in the pathogenesis. We investigated Th2 cytokine synthesis by mononuclear cells and possible Th1/Th2 subpopulations in Kimuras disease. Peripheral blood samples were obtained from seven patients with Kimuras disease and CD4(+) T-cell subpopulations separated by CD45RO and CD62L were isolated. Purified cells were stimulated with PHA or anti-CD3 mAb, and the cytokine levels were measured by Cytometric Bead Array kit. Peripheral blood mononuclear cells in the majority of the patients produced Th2 cytokines such as interleukin (IL)-3, IL-4, IL-5, IL-13 or GM-CSF higher than those of controls. The ratio of CD45RO(+) CD62L(+) cells in CD4(+) T cells was increased in six out of seven patients compared to age-matched controls. Especially, patient 1 had remarkably increased levels of CD45RO(+) CD62L(+) population in CD4(+) T cells. In addition, IL-4 production levels by CD45RO(+) CD62L(+) CD4(+) T cells of patients 1 and 2 were higher than those of their CD45RO(+) CD62L(-) CD4(+) T cells, in the same manner as those by a normal control. Taken together, the synthesis of Th2 cytokines and CD62L-positive subpopulation in CD45RO(+) CD4(+) T cells, which may represent characteristics of Th2, are increased in patients with Kimuras disease, suggesting that deviation to Th2 may involve in pathogenesis of the disease.

Complete arrest from pro‐ to pre‐B cells in a case of B cell‐negative severe combined immunodeficiency (SCID) without recombinase activating gene (RAG) mutations

The B‐cell lineage in a patient with B‐cell‐negative severe combined immunodeficiency (SCID) was analysed by using antisurrogate light chain (SL) MoAbs. Peripheral CD3+ T cells and CD19+ B cells were absent in the patient. The common gamma (γc) chain was expressed normally on the patients peripheral NK cells and his peripheral mononuclear cells did not possess any mutations in recombinase activating gene (RAG)‐1, 2. Normal levels of expression of Ku70 and Ku80 protein were found by Western blot analysis. The patient did, however, display an increase in fibroblast sensitivity to irradiation. Furthermore, flow cytometric analyses of bone marrow cells showed that surface IgM and cytoplasmic µ positive cells were absent and that CD19+ B cells were composed of only CD34+ terminal deoxynucleotidyl transferase (TdT)+ SL+ pro‐B cells. The complete arrest of pro‐ to pre‐B cell development in the SCID patients bone marrow suggests that some genes involved in V(D)J recombination, excepting the RAG gene, may play a causative role in the immunodeficiency.

Markedly elevated CD64 expression on neutrophils and monocytes as a biomarker for diagnosis and therapy assessment in Kawasaki disease

ObjectiveKawasaki disease (KD) is the most commonly encountered inflammatory disease in children. However, its pathogenesis and diagnostic biomarkers have not been fully investigated. We examined the activation of neutrophils and monocytes in KD.MethodsWe studied the expression of the Fcγ-receptors CD64 and CD16 on neutrophils and monocytes in KD before and after the treatment with intravenous infusion of high dose immunoglobulin (IVIG). Bacterial infections were addressed as well.ResultsCD64 expression on neutrophils and monocytes was dramatically increased at the onset of KD flare-ups, but later decreased just after IVIG. Similarly, CD16-positive monocytes were observed at the onset and were less apparent after therapy. The addition of immunoglobulin did not block the expression of CD64 or CD16 in vitro. Serum G-CSF in the majority of patients, and IFN-γ in some patients, were elevated during flares but decreased after treatment.ConclusionOur findings demonstrate that remarkable CD64 expression during KD flare-ups may serve as a biomarker for diagnosis. Evaluation of CD64 is also potentially useful for the determination of treatment efficacy in KD.