CD1 expression defines subsets of follicular and marginal zone B cells in the spleen: beta 2-microglobulin-dependent and independent forms

We have used multicolor FACS analysis, immunohistology, and functional assays to study the expression of CD1 on B cell subsets from normal and beta 2m-/- mice. Two B cell subpopulations were identified that express high levels of CD1 in normal mice: splenic marginal zone B cells (IgMhigh IgDlow CD21high CD24intermediate CD23- CD43-) and a newly identified subpopulation of follicular B cells. The latter cells are unusual, because they are IgDhigh CD23+, like follicular B cells, but express high levels of CD21 and IgM, an expression pattern that is associated with marginal zone B cells. Therefore, the high-level expression of CD1 and CD21 was found to be closely associated on splenic B cells. Immunohistology confirmed the expression of CD1 on marginal zone B cells and on clusters of B cells in splenic follicles. Both the high-level CD1 expression by these cells and the low-level CD1 expression by subpopulations of B cells in the spleen, lymph node, peritoneal cavity, and bone marrow were markedly reduced in beta 2m-/- mice. Despite this, a CD1-restricted T cell clone proliferated vigorously in response to LPS-activated spleen cells that had been obtained from both beta 2m-/- and wild-type mice. This response was inhibited by the 3C11 anti-CD1 mAb. These results show the heterogeneity of B cell subsets in their expression of the beta 2m-dependent form of CD1. They further suggest that a beta 2m-independent form of CD1 is expressed on B cells that can stimulate T cells; however, this form is not easily visualized with the anti-CD1 mAb used here.     

Active Wegener's granulomatosis is associated with HLA-DR+ CD4+ T cells exhibiting an unbalanced Th1-type T cell cytokine pattern: reversal with IL-10

Wegener's granulomatosis (WG) is a granulomatous vasculitis that affects the upper respiratory tract, lung, and kidney. Since T cells make up a significant proportion of cells infiltrating granulomatous lesions in WG, we investigated the proliferative response and cytokine profile of T cells from these patients. PBMCs were isolated from 12 patients with active WG, 7 patients with inactive disease, and 12 healthy normal donors. PBMCs from clinically active WG patients exhibited increased proliferation following stimulation with either PMA/ionomycin or anti-CD2 and anti-CD28, when compared with normal donors. In addition, these PBMCs exhibited increased secretion of IFN-gamma, but not of IL-4, IL-5, or IL-10. Furthermore, TNF-alpha production from PBMCs and CD4+ T cells isolated from patients with WG was elevated, when compared with healthy donors. In further studies, we investigated the ability of WG patients' monocytes to produce IL-12 and showed that both inactive and active patients produced increased amounts of IL-12. Finally, the in vitro IFN-gamma production by WG PBMC is inhibited in a dose-dependent manner by exogenous IL-10. These data suggest that T cells from WG patients overproduce IFN-gamma and TNF-alpha, probably due to dysregulated IL-12 secretion, and that IL-10 may therefore have therapeutic implications for this disease.     

Pathological findings in human autoimmune lymphoproliferative syndrome

The defects in lymphocyte apoptosis that underlie the autoimmune lymphoproliferative syndrome (ALPS) are usually attributable to inherited mutations of the CD95 (Fas) gene. In this report, we present the histopathological and immunophenotypic features seen in the lymph nodes (n = 16), peripheral blood (n = 10), bone marrow (n = 2), spleen (n = 3), and liver (n = 2) from 10 patients with ALPS. Lymph nodes showed marked paracortical hyperplasia. Interfollicular areas were expanded and populated by T cell receptor-alphabeta CD3+ CD4-CD8- (double-negative, DN) T cells that were negative for CD45RO. CD45RA+ T cells were increased in all cases studied. The paracortical infiltrate was a result of both reduced apoptosis and increased proliferation, as measured by in situ detection of DNA fragmentation and staining with MIB-1, respectively. The paracortical proliferation may be extensive enough to suggest a diagnosis of malignant lymphoma. Many of the paracortical lymphocytes expressed markers associated with cytotoxicity, such as perforin, TIA-1, and CD57. CD25 was negative. In addition, most lymph nodes exhibited florid follicular hyperplasia, often with focal progressive transformation of germinal centers; in some cases, follicular involution was seen. A polyclonal plasmacytosis also was present. The spleens were markedly enlarged, more than 10 times normal size. There was expansion of both white pulp and red pulp, with increased DN T cells. DN T cells also were observed in liver biopsies exhibiting portal triaditis. In the peripheral blood, the T cells showed increased expression of HLA-DR and CD57 but not CD25. CD45RA+ T cells were increased in the four cases studied. Polyclonal B cell lymphocytosis with expansion of CD5+ B cells was a characteristic finding. Taken together, the histopathological and immunophenotypic findings, particularly in lymph nodes and peripheral blood, are sufficiently distinctive to suggest a diagnosis of ALPS. Of note, two affected family members of one proband developed lymphoma (T-cell-rich B-cell lymphoma and nodular lymphocyte predominance Hodgkin's disease, respectively).     

The metabolism of IgE. Studies in normal individuals and in a patient with IgE myeloma

IgE metabolic turnover studies with purified radioiodinated IgE were performed in normal individuals and in a patient with IgE myeloma. The validity of the turnover studies was established in several ways, including comparisons of radioiodinated IgE turnover with the turnover of endogenously labeled 14C-IgE and with the turnover of infused unlabeled IgE in a patient with hypogammaglobulinemia. The geometric mean serum IgE concentration in 73 normal adults was 96 ng/ml with a 68% confidence interval of 24 to 386 ng/ml. Metabolic turnover studies in 10 control individuals disclosed a geometric mean total circulating IgE of 4.1 mug/kg, a mean percentage of the total exchangeable IgE in the intravascular space of 41%, a mean half-time of survival of IgE of 2.7 days, a mean fractional catabolic rate of 94% of intravascular pool per day, and a geometric mean synthetic rate of 3.8 mug/kg/day. IgE has the lowest synthetic rate and highest fractional catabolic rate of the five major classes of immunoglobulin molecules. In contrast to these normal values, a patient with IgE myeloma had a serum IgE comcentration of 42 mg/ml, a total circulating IgE of 1.7 g/kg, and a synthetic rate of 270 mg/kg/day. Furthermore, although the synthetic rate was vastly increased, the survival time was prolonged and the fractional catabolic rate was decreased to 5.1 days and 16 to 22% of the intravascular pool per day, respectively. These data are compatible with the concept that IgE is catabolized in part by a mechanism common to all immunoglobulin classes and in part by a unique mechanism not available to other immunoglobulins. At very high IgE serum concentrations, such as those encountered in patients with IgE myeloma, the unique mechanism would be saturated and only the catabolic pathways available to all immunoglobulins would be available to IgE.     

The T cell-B cell interaction via OX40-OX40L is necessary for the T cell-dependent humoral immune response

Recent in vitro studies have established that activated B cells express OX40 ligand (L), a member of the tumor necrosis factor/nerve growth factor family of cytokines, and become stimulated to proliferate and secrete immunoglobulin (Ig) after cross-linking of OX40L by its counterreceptor OX40, which is expressed on activated T cells. In the present study we investigated the in vivo role of this receptor-ligand pair for the interaction of T and B cells in the course of the T-dependent B cell response against 2,4,6 trinitro-phenyl-keyhole limpet hemocyanin. First, we showed that OX40 is maximally expressed by T cells in the periarteriolar lymphoid sheath (PALS) 3 d after primary immunization. These OX40+ cells are located in close proximity to antigen-specific, activated B cells. Second, we demonstrated that blocking of OX40-OX40L interaction with polyclonal anti-OX40 antibody or with antibodies against certain peptide sequences within its extracellular domain resulted in a profound decrease of the anti-hapten IgG response, whereas the antihapten IgM response was grossly unchanged. Third, we showed that this antibody treatment leads to an inhibition of the development of PALS-associated B cell foci, whereas the formation of germinal centers remained intact. Finally, our data suggest that, whereas B cell memory development was not impaired by anti-OX40 administration, OX40-OX40L interaction seems to be crucial in the secondary immune response. We conclude from these data that the OX40-OX40L interaction in vivo is necessary for the differentiation of activated B cells into highly Ig-producing cells, but is not involved in other pathways of antigen-driven B cell differentiation such as memory cell development in the germinal centers.     

Intestinal lymphangiectasia, a disease characterized by selective loss of naive CD45RA+ lymphocytes into the gastrointestinal tract

Intestinal lymphangiectasia (InL) is a disease characterized by hypoproteinemia and lymphocytopenia resulting from blocked intestinal lymphatics and loss of lymph fluid into the gastrointestinal tract. This leads to immunologic abnormalities including hypogammaglobulinemia, skin anergy and impaired allograft rejection. In the present study, we evaluated whether the above immunologic abnormalities are secondary to a quantitative or qualitative disorder of T cells. In initial studies we demonstrated that adult InL patients' peripheral blood contain strikingly (and significantly) reduced numbers of CD4+/CD45RA+ T cells, whereas the numbers of CD4+/CD45RO+ T cells were only moderately (and not significantly) reduced. In addition, the CD4+/CD45RO+ T cell population contained an increased percentage of highly differentiated and previously sensitized cells, as demonstrated by decreased CD27 and CD31 expression and increased HLA-DR and CD69 expression. In subsequent functional studies, we showed that the InL CD4+/CD45RO+ T cells, when stimulated in vitro, proliferate fivefold less than control CD4+/CD45RO+ T cells and produce fourfold more IL-4 and threefold less IFN-gamma and IL-2. Thus, this cytokine production profile also reflects the highly differentiated nature of the residual cell population. Overall, these studies provide new information on the trafficking of naive/mature and Th1/Th2 T cell populations in this disease model.     

Utility of the Beck Depression Inventory with psychiatrically hospitalized adolescents.

Investigated whether the Beck Depression Inventory (BDI) is a psychometrically sound instrument for measuring depressive symptomatology in 78 12–16 yr old psychiatrically disturbed adolescents. Test–retest, item-total, and coefficient alpha estimates of reliability were found to be statistically acceptable. BDI scores discriminated between patients with a hospital diagnosis of major depressive disorder and a diagnostically heterogeneous group of patients with nonaffective conditions. Results suggest that the BDI can be used profitably in clinical and treatment studies of depressive phenomena in early adolescence. (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An alternate pathway for T cell development supported by the bone marrow microenvironment: recapitulation of thymic maturation

In the principal pathway of alpha/beta T cell maturation, T cell precursors from the bone marrow migrate to the thymus and proceed through several well-characterized developmental stages into mature CD4+ and CD8+ T cells. This study demonstrates an alternative pathway in which the bone marrow microenvironment also supports the differentiation of T cell precursors into CD4+ and CD8+ T cells. The marrow pathway recapitulates developmental stages of thymic maturation including a CD4+CD8+ intermediary cell and positive and negative selection, and is strongly inhibited by the presence of mature T cells. The contribution of the marrow pathway in vivo requires further study in mice with normal and deficient thymic or immune function.