Divergent immunohistochemical expression of CD21 and CD23 by follicular dendritic cells with increasing grade of follicular lymphoma.

BACKGROUND: Ultrastructural and immunohistochemical differences have been described in FDCs of primary and secondary follicles, illustrating the highly compartmentalized structure of lymph follicles. Differences in FDC immunophenotype in different grades of FL may reflect some parallelism between reactive and neoplastic conditions in terms of FDC-B cell interaction and may be used as a valuable additional tool for grading FL. METHODS: A total of 60 paraffin blocks from patients with follicular lymphoma, 30 cases each of grade 1 and 3, were retrieved from our archive. Immunohistochemical analysis was carried out for CD21, CD23, cyclin A, and Ki-67. RESULTS: Our study demonstrates that during evaluation, six patterns of FDC distribution were distinguished. The intensity of stain for CD21 was not statistically significant in grade 1 and grade 3 FL (p = 0.340). In contrast, grade 3 FLs exhibited a significant decrease of CD23 expression by the FDCs (p < 0.001). By CD21 stain, there was no significant difference in the distribution of pattern 1 in grades 1 and 3 (p = 0.098). In contrast, in grade 3, this pattern was significantly less observed by CD23 stain (p = 0.016). The same was observed for pattern 2 for CD21 (p = 0.940) and CD23 (p = 0.010) and pattern 4 for CD21 (p = 0.305) and CD23 (p = 0.005), respectively. Distribution of pattern 5 was significantly different between grades 1 and 3 both for CD21 (p = 0.005) and CD23 (p < 0.001). Distribution of patterns 2 and 6 was not significantly different between grades 1 and 3 for CD21 and CD23. The values of cyclin A and Mib-1 were also significantly different between grades 1 and 3 (p < 0.001). CONCLUSIONS: The observed patterns of FDCs lead us to believe that similar to reactive lymph node follicles, neoplastic follicles in FL, at least in early stages, have an organized structure. Hypothetically, with CD21, CD23, and cyclin A immunohistochemistry, the sequence of events in FL progression may be traced.

Mast cell differentiation: still open questions?

In this issue of Blood, Dahlin et al report on a minor circulating human mast cell (MC) progenitor cell population (lineage-negative [Lin−]/CD34hi/CD117int/hi/high-affinity immunoglobulin E receptor-positive [FcεRI+]), with an immature MC-like appearance, which is present in the peripheral blood (PB) of healthy individuals and of asthma subjects well controlled by treatment or with reduced lung function.

Lin- CD34hi CD117int/hi FcεRI+ cells in human blood constitute a rare population of mast cell progenitors.

Mast cells are rare tissue-resident immune cells that are involved in allergic reactions, and their numbers are increased in the lungs of asthmatics. Murine lung mast cells arise from committed bone marrow-derived progenitors that enter the blood circulation, migrate through the pulmonary endothelium, and mature in the tissue. In humans, mast cells can be cultured from multipotent CD34(+) progenitor cells. However, a population of distinct precursor cells that give rise to mast cells has remained undiscovered. To our knowledge, this is the first report of human lineage-negative (Lin(-)) CD34(hi) CD117(int/hi) FcεRI(+) progenitor cells, which represented only 0.0053% of the isolated blood cells in healthy individuals. These cells expressed integrin ß7 and developed a mast cell-like phenotype, although with a slow cell division capacity in vitro. Isolated Lin(-) CD34(hi) CD117(int/hi) FcεRI(+) blood cells had an immature mast cell-like appearance and expressed high levels of many mast cell-related genes as compared with human blood basophils in whole-transcriptome microarray analyses. Furthermore, serglycin, tryptase, and carboxypeptidase A messenger RNA transcripts were detected by quantitative reverse transcription-polymerase chain reaction. Altogether, we propose that the Lin(-) CD34(hi) CD117(int/hi) FcεRI(+) blood cells are closely related to human tissue mast cells and likely constitute an immediate precursor population, which can give rise to predominantly mast cells. Furthermore, asthmatics with reduced lung function had a higher frequency of Lin(-) CD34(hi) CD117(int/hi) FcεRI(+) blood mast cell progenitors than asthmatics with normal lung function.

Lymphoma-like monoclonal B cell lymphocytosis in a patient population: biology, natural evolution, and differences from CLL-like clones.

High-count monoclonal B cell lymphocytosis (MBL) with a chronic lymphocytic leukemia (CLL) phenotype is a well-known entity, featuring 1-4% annual risk of progression towards CLL requiring treatment. Lymphoma-like MBL (L-MBL), on the other hand, remains poorly defined and data regarding outcome are lacking. We retrospectively evaluated 33 L-MBL cases within our hospital population and compared them to 95 subjects with CLL-like MBL (C-MBL). Diagnoses of L-MBL were based on asymptomatic B cell clones with Matutes score < 3, B cells < 5.0 × 103/µl, and negative computerized tomography scans. We found that median B cell counts were considerably lower compared to C-MBL (0.6 vs 2.3 × 103/µl) and remained stable over time. Based on immunophenotyping and immunogenetic profiling, most L-MBL clones did not correspond to known lymphoma entities. A strikingly high occurrence of paraproteinemia (48%), hypogammaglobulinemia (45%), and biclonality (21%) was seen; these incidences being significantly higher than in C-MBL (17, 21, and 5%, respectively). Unrelated monoclonal gammopathy of undetermined significance was a frequent feature, as the light chain type of 5/12 paraproteins detected was different from the clonal surface immunoglobulin. After 46-month median follow-up, 2/24 patients (8%) had progressed towards indolent lymphoma requiring no treatment. In contrast, 41% of C-MBL cases evolved to CLL and 17% required treatment. We conclude that clinical L-MBL is characterized by pronounced immune dysregulation and very slow or absent progression, clearly separating it from its CLL-like counterpart.

Characterization of a variant of t(14;18) negative nodal diffuse follicular lymphoma with CD23 expression, 1p36/TNFRSF14 abnormalities, and STAT6 mutations.

A predominantly diffuse growth pattern and CD23 co-expression are uncommon findings in nodal follicular lymphoma and can create diagnostic challenges. A single case series in 2009 (Katzenberger et al) proposed a unique morphologic variant of nodal follicular lymphoma, characterized by a predominantly diffuse architecture, lack of the t(14;18) IGH/BCL2 translocation, presence of 1p36 deletion, frequent inguinal lymph node involvement, CD23 co-expression, and low clinical stage. Other studies on CD23+ follicular lymphoma, while associating inguinal location, have not specifically described this architecture. In addition, no follow-up studies have correlated the histopathologic and cytogenetic/molecular features of these cases, and they remain a diagnostic problem. We identified 11 cases of diffuse, CD23+ follicular lymphoma with histopathologic features similar to those described by Katzenberger et al. Along with pertinent clinical information, we detail their histopathology, IGH/BCL2 translocation status, lymphoma-associated chromosomal gains/losses, and assessment of mutations in 220 lymphoma-associated genes by massively parallel sequencing. All cases showed a diffuse growth pattern around well- to ill-defined residual germinal centers, uniform CD23 expression, mixed centrocytic/centroblastic cytology, and expression of at least one germinal center marker. Ten of 11 involved inguinal lymph nodes, 5 solely. By fluorescence in situ hybridization analysis, the vast majority lacked IGH/BCL2 translocation (9/11). Deletion of 1p36 was observed in five cases and included TNFRSF14. Of the six cases lacking 1p36 deletion, TNFRSF14 mutations were identified in three, highlighting the strong association of 1p36/TNFRSF14 abnormalities with this follicular lymphoma variant. In addition, 9 of the 11 cases tested (82%) had STAT6 mutations and nuclear P-STAT6 expression was detectable in the mutated cases by immunohistochemistry. The proportion of STAT6 mutations is higher than recently reported in conventional follicular lymphoma (11%). These findings lend support for a clinicopathologic variant of t(14;18) negative nodal follicular lymphoma and suggests importance of the interleukin (IL)-4/JAK/STAT6 pathway in this variant.

Phenotypic variability in human skin mast cells.

Mast cells (MCs) are unique constituents of the human body. While inter-individual differences may influence the ways by which MCs operate in their skin habitat, they have not been surveyed in a comprehensive manner so far. We therefore set out to quantify skin MC variability in a large cohort of subjects. Pathophysiologically relevant key features were quantified and correlated: transcripts of c-kit, FcεRIα, FcεRIß, FcεRIγ, histidine decarboxylase, tryptase, and chymase; surface expression of c-Kit, FcεRIα; activity of tryptase, and chymase; histamine content and release triggered by FcεRI and Ca(2+) ionophore. While there was substantial variability among subjects, it strongly depended on the feature under study (coefficient of variation 33-386%). Surface expression of FcεRI was positively associated with FcεRIα mRNA content, histamine content with HDC mRNA, and chymase activity with chymase mRNA. Also, MC signature genes were co-regulated in distinct patterns. Intriguingly, histamine levels were positively linked to tryptase and chymase activity, whereas tryptase and chymase activity appeared to be uncorrelated. FcεRI triggered histamine release was highly variable and was unrelated to FcεRI expression but unexpectedly tightly correlated with histamine release elicited by Ca(2+) ionophore. This most comprehensive and systematic work of its kind provides not only detailed insights into inter-individual variability in MCs, but also uncovers unexpected patterns of co-regulation among signature attributes of the lineage. Differences in MCs among humans may well underlie clinical responses in settings of allergic reactions and complex skin disorders alike.

Blastic marginal zone lymphoma: a clinical and pathological study of 8 cases and review of the literature.

INTRODUCTION: Blastic transformation (BT) of marginal zone lymphoma or mucosa-associated lymphoid tissue lymphoma has been mainly reported in the spleen and stomach. Primary cutaneous marginal zone lymphoma that undergoes BT is rare and not well documented. We describe 8 patients with blastic primary cutaneous marginal zone lymphoma and compare the clinical, pathologic, and molecular findings of these patients with 10 cases previously reported in the literature. RESULTS: The cases of blastic marginal zone lymphoma could be categorized into cases of de novo blastic marginal zone lymphoma and large-cell transformation arising in a background of a history of biopsy proven marginal zone lymphoma. The cases of de novo blastic marginal zone lymphoma occurred in elderly patients without any medical history. In each of the cases, the lesions were radiated, not treated, or treated with complete excision without any death due to lymphoma nor was there any evidence of extracutaneous dissemination. Large-cell transformation arising in background of marginal zone lymphoma typically occurred in patients who were younger; 2 of the 4 cases were immunocompromised. The clinical course in each of the cases was aggressive with 3 of the 4 patients succumbing to disseminated disease while 1 patient developed extracutaneous nodal disease. Phenotypically, there was an expression of CD5 in a total of 3 of the 8 cases and CD23 in 3 of the 8 cases. Commonality of B-cell clones was demonstrated in 2 cases where biopsies were available of both the less aggressive appearing marginal zone lymphoma and the transformed biopsies. Cytogenetic abnormalities associated with BT included a deletion of chromosome 7q in all cases tested. CONCLUSION: Large-cell transformation arising in a patient with a history of marginal zone lymphoma portends a worse prognosis, including death from disseminated disease, whereas a de novo presentation of blastic marginal zone lymphoma may define a clinical course similar to other forms of low-grade cutaneous B-cell lymphoma. The expression of CD5 and CD23 may define a phenotypic profile associated with BT. It is possible that marginal zone lymphomas associated with CD5 and CD23 positivity should be followed more closely and/or treated with radiation and/or complete excision.

A time-resolved fluorescence resonance energy transfer assay suitable for high-throughput screening for inhibitors of immunoglobulin E-receptor interactions.

The interaction of immunoglobulin E (IgE) antibodies with the high-affinity receptor, FcεRI, plays a central role in initiating most allergic reactions. The IgE-receptor interaction has been targeted for treatment of allergic diseases, and many high-affinity macromolecular inhibitors have been identified. Small molecule inhibitors would offer significant advantages over current anti-IgE treatment, but no candidate compounds have been identified and fully validated. Here, we report the development of a time-resolved fluorescence resonance energy transfer (TR-FRET) assay for monitoring the IgE-receptor interaction. The TR-FRET assay measures an increase in fluorescence intensity as a donor lanthanide fluorophore is recruited into complexes of site-specific Alexa Fluor 488-labeled IgE-Fc and His-tagged FcεRIα proteins. The assay can readily monitor classic competitive inhibitors that bind either IgE-Fc or FcεRIα in equilibrium competition binding experiments. Furthermore, the TR-FRET assay can also be used to follow the kinetics of IgE-Fc-FcεRIα dissociation and identify inhibitory ligands that accelerate the dissociation of preformed complexes, as demonstrated for an engineered DARPin (designed ankyrin repeat protein) inhibitor. The TR-FRET assay is suitable for high-throughput screening (HTS), as shown by performing a pilot screen of the National Institutes of Health (NIH) Clinical Collection Library in a 384-well plate format.

[Chronic lymphocytic leukaemia presenting with specific cutaneous infiltrates in the absence of lymphocytosis: Two cases]. / Leucémie lymphoïde chronique révélée par des infiltrats cutanés spécifiques en l'absence d'hyperlymphocytose : deux observations.

BACKGROUND: Specific cutaneous infiltrates of chronic lymphocytic leukaemia (CLL) are rare. They occur after a mean disease duration of 3 years. CLL skin infiltrates as the primary manifestation of the disease have been reported, but a normal lymphocyte count at diagnosis is rare. We present two cases of CLL initially presenting in the skin, without lymphocytosis. PATIENTS AND METHODS: A 53-year-old man developed papulonodular lesions of the face and infiltrated plaques of the scalp, and an 85-year-old woman presented erythematous nodules of the face and neck. Histopathology revealed a lymphocytic infiltrate, consisting of small mature B-cells CD20+, CD79+, with an aberrant phenotype CD5+. CD23 was positive in one case. The two patients had no lymphocytosis, but immunophenotyping was characteristic of CLL. In the second case, there was a sub-mental adenopathy, histologic analysis of which was consistent with CLL. The CLL was classified as Binet stage A in the two cases. No disease progression was noted at follow-up. DISCUSSION: The unusual feature of these cases is the lack of lymphocytosis at diagnosis. Thus, the skin lesions resulted in further evaluations for CLL, although the diagnosis was not suggested by the blood count. CONCLUSION: Skin involvement in CLL does not appear to be a poor prognostic indicator, arguing in favour of recruitment of circulating monoclonal B-cells rather than an additional tumour mass.

Tetraspanins CD9 and CD81 are molecular partners of trimeric FcɛRI on human antigen-presenting cells.

BACKGROUND: Most functions of tetraspanins are not related to cell-surface receptor ligand binding, but are mediated by direct interactions with their partner proteins. Functions of trimeric FcɛRI, expressed by antigen-presenting cells (APCs), range from amplification of allergic inflammatory reactions to their active suppression. Cell-type-specific protein-protein interactions might play a role in the regulation of these bidirectional tasks. Therefore, we intended to study the interactions of trimeric FcɛRI with tetraspanins. METHODS: The expression levels of tetraspanins CD9, CD37, CD53, CD63, CD81, CD82, and CD151 on skin dendritic cells of atopic dermatitis (AD) patients or healthy individuals were detected by flow cytometry. Tetraspanin expression on FcɛRI(pos) and FcɛRI(neg) monocyte subpopulations was evaluated. Flow cytometry, confocal microscopy, immunoprecipitation, and immunoblotting experiments were performed to observe the relationship between tetraspanins CD9 and CD81 and FcɛRI. Furthermore, plate stimulation experiments were performed, and cytokines in the supernatants were detected. RESULTS: We found that human FcɛRI(pos) APCs expressed high amounts of tetraspanins and that the tetraspanins CD9 and CD81 were associated with FcɛRI. Concomitant activation of FcɛRI and CD9 on human monocytes increased FcɛRI-mediated cytokine release. CONCLUSION: Taken together, we show for the first time that CD9 and CD81 act as molecular partners of trimeric FcɛRI on human APC, which might be of importance in allergic diseases such as AD.

IgE-dependent and IgE-independent stimulation of human basophils increases the presence of immature FcεRIα by reversing degradative pathways.

BACKGROUND: Expression of the high-affinity IgE receptor, FcεRI, on mast cells and basophils has previously been shown to be sensitive to the presence of IgE or cytokines. The current study examined whether stimulation of human basophils resulted in a change in the expression of FcεRI. METHODS: Changes in the well-expressed immature intracellular form of the receptor, FcεRIα (p46), were examined by quantitative PCR, Western blot and the pulse-chase method. RESULTS: Both IgE-dependent (anti-IgE antibody) and IgE-independent stimulation [formyl-methionyl-leucyl-phenylalanine (FMLP) and C5a] led to increased accumulation of p46. The p46 form of FcεRIα increased 1.52 ± 0.09-, 2.58 ± 0.09- and 1.47 ± 0.07-fold following stimulation with anti-IgE, FMLP and C5a, respectively. There were no changes in the steady-state levels of mRNA for FcεRIα. The kinetics of the increase in p46 was slow following stimulation with anti-IgE antibody, with the earliest increases observed after 8 h. The p46 form was degraded in a bafilomycin A (lysosomal inhibitor)-sensitive process. There was no synergy between treatment with bafilomycin A and anti-IgE or FMLP stimulation, suggesting that the 2 methods of enhancement operate on the same pathway. Pulse-chase studies corroborated this conclusion. In contrast, IL-3 and bafilomycin A synergistically increased p46, suggesting that IL-3 increased synthesis of FcεRIα. CONCLUSIONS: Taken together, these results suggest that secretagogue stimulation results in an increase in p46 due to reversal of degradative pathways rather than increased synthesis of FcεRIα. Nevertheless, a decrease in the degradation of FcεRIα at an intermediate step in its processing by non-FcεRI-dependent stimulation may still influence expression of this important receptor.

Immune pathways for translating viral infection into chronic airway disease.

To better understand the immune basis for chronic inflammatory lung disease, we analyzed a mouse model of lung disease that develops after respiratory viral infection. The disease that develops in this model is similar to asthma and chronic obstructive pulmonary disease (COPD) in humans and is manifested after the inciting virus has been cleared to trace levels. The model thereby mimics the relationship of paramyxoviral infection to the development of childhood asthma in humans. When the acute lung disease appears in this model (at 3 weeks after viral inoculation), it depends on an immune axis that is initiated by expression and activation of the high-affinity IgE receptor (FcvarepsilonRI) on conventional lung dendritic cells (cDCs) to recruit interleukin (IL)-13-producing CD4(+) T cells to the lower airways. However, when the chronic lung disease develops fully (at 7 weeks after inoculation), it is driven instead by an innate immune axis that relies on invariant natural killer T (iNKT) cells that are programmed to activate macrophages to produce IL-13. The interaction between iNKT cells and macrophages depends on contact between the semi-invariant Valpha14Jalpha18-TCR on lung iNKT cells and the oligomorphic MHC-like protein CD1d on macrophages as well as NKT cell production of IL-13 that binds to the IL-13 receptor (IL-13R) on the macrophage. This innate immune axis is also activated in the lungs of humans with severe asthma or COPD based on detection of increased numbers of iNKT cells and alternatively activated IL-13-producing macrophages in the lung. Together, the findings identify an adaptive immune response that mediates acute disease and an innate immune response that drives chronic inflammatory lung disease in experimental and clinical settings.

Cervical follicular dendritic cell sarcoma: a case report and review of the literature.

Follicular dendritic cell (FDC) sarcoma is a rare tumour with a low-to-intermediate grade of malignancy. It frequently occurs in cervical, mediastinal and axillary lymph nodes. In approximately 30% of cases an extranodal localization has been reported (tonsils, oral cavity, mediastinum, liver, and spleen). Very little is known about possible treatment options and overall prognosis. This case reports a 66 year-old patient, who underwent surgical removal of a persistently enlarged right cervical lymph node. The histopathological examination revealed a spindle cell tumour with lymphocyte and plasma cell infiltrates. Neoplastic cells stained positive for CD21, CD23 and CD35, thus confirming the diagnosis of FDC sarcoma. The neoplasm recurred two years later and partial regression was achieved by IGEV rescue therapy. We briefly discuss clinical history, histopathological differential diagnosis and treatment options of FDC sarcoma.

Increases in levels of schistosome-specific immunoglobulin E and CD23(+) B cells in a cohort of Kenyan children undergoing repeated treatment and reinfection with Schistosoma mansoni.

BACKGROUND: Age prevalence curves for areas in which schistosomiasis is endemic suggest that humans develop partial immunity to reinfection beginning in early adolescence. We conducted a 2-year longitudinal study to determine whether children infected with Schistosoma mansoni develop protection-related immune responses after treatment with praziquantel and whether the development of these immune responses is accelerated by frequent treatment after reinfection. METHODS: Children (8-10 years old) were tested for S. mansoni every 4 months and treated with praziquantel when positive (arm A; n=68) or were tested and treated at the end of the 2-year follow-up period (arm B; n=49). RESULTS: Children in arm A who remained free of infection during follow-up had significantly higher baseline levels of schistosome-specific immunoglobulin E (IgE) than did children with > or =2 repeat diagnoses of S. mansoni infection. Children with > or =2 repeat diagnoses of S. mansoni infection had significantly increased levels of anti-schistosome IgE and CD23(+) B cells after receiving > or =3 praziquantel treatments over the course of follow-up. No increase in either parameter was seen in children who received only the baseline praziquantel treatment. CONCLUSIONS: B cell activation and anti-schistosome IgE are associated with resistance to S. mansoni in children, and these immunological parameters can be increased by multiple rounds of infections and praziquantel-induced cures.

Basophils as a potential therapeutic target in cancer.

Basophils, which are considered as redundant relatives of mast cells and the rarest granulocytes in peripheral circulation, have been neglected by researchers in the past decades. Previous studies have revealed their vital roles in allergic diseases and parasitic infections. Intriguingly, recent studies even reported that basophils might be associated with cancer development, as activated basophils synthesize and release a variety of cytokines and chemokines in response to cancers. However, it is still subject to debate whether basophils function as tumor-protecting or tumor-promoting components; the answer may depend on the tumor biology and the microenvironment. Herein, we reviewed the role of basophils in cancers, and highlighted some potential and promising therapeutic strategies.

A new score including CD43 and CD180: Increased diagnostic value for atypical chronic lymphocytic leukemia.

Moreau score has been used to differentiate chronic lymphocytic leukemia (CLL) from other mature B-cell neoplasms. However, it showed limitations in Asian patients. Therefore, we conducted a new score system replacing CD5 and CD23 with CD43 and CD180 to evaluate its diagnostic value of CLL. 237 untreated samples diagnosed with mature B-cell neoplasms were collected and were randomly divided into an exploratory and a validation cohort by a 2:1 ratio. The expression of CD5, CD19, CD20, CD23, CD43, CD79b, CD180, CD200, FMC7, and surface immunoglobulin (SmIg) were analyzed among all the samples. A proposed score was developed based on the logistic regression model. The sensitivity and specificity of the proposed score were calculated by ROC curves. CD43/CD180, CD200, FMC7, and CD79b were included in our new CLL score, which showed a sensitivity of 91.8% and a specificity of 83.1%. These results were confirmed in a validation cohort with a sensitivity of 90.5% (p = 0.808) and a specificity of 79.5% (p = 0.639). In CD5 negative or CD23 negative CLL group, the new CLL score displayed improved sensitivity of 79.4% compared to Moreau score and CLLflow score (41.2% and 47.1%, respectively). In atypical CLL group, the new CLL score showed improved sensitivity of 84.2% compared to Moreau score and CLLflow score (61.4% and 64.9%, respectively). This proposed atypical CLL score helped to offer an accurate differentiation of CLL from non-CLL together with morphological and molecular methods, particularly in Chinese patients with atypical immunophenotype.

Evidence for an interleukin 4-inducible immunoglobulin E uptake and transport mechanism in the intestine.

Immunoglobulin (Ig) E is the principal Ig involved in immediate hypersensitivities and chronic allergic diseases such as asthma. Helminths are the most potent infectious agents known for their capacity to stimulate IgE production during the course of infection. In rats, the nematode Trichinella spiralis typically elicits a strong parasite-specific IgE response during infection, and this IgE antibody has been shown to be protective against the parasite in passive transfer experiments. The study reported here analyzed the fate of 125I-labeled myeloma IgE (1R162) in normal and T. spiralis-infected rats after intravenous injection. T. spiralis infection induced a capacity for specific binding to the gut wall of 125I-IgE rather than 125I-IgG1, as well as the transport of IgE, but not IgG1, into the gut lumen. Peak intestinal uptake and transport of 125I-IgE occurred during the first and second weeks after injection but was not elevated in the fourth week, that is, after intestinal adult worms had been expelled. Neither 125I-IgE uptake in the gut wall nor transport to the lumen could be ascribed to tissue damage or vascular leakage. Luminal transport occurred in the small intestine and not the liver, which only transports low molecular weight degraded 125I-IgE. Calculations based on the amount of intact IgE in the lumen suggest that, in a 24-h period, up to 20% of injected 125I-IgE can be transported to the gut lumen during the peak transport period, between 6 and 14 d after infection. The intestinal IgE binding and transport response can be adoptively transferred with T. spiralis immune CD4+ OX22- (CD45RC-) lymphocytes, which are protective, but not the nonprotective sister population CD4+ OX22+ (CD45RC+) of lymphocytes isolated simultaneously from thoracic duct lymph of infected rats. The intravenous infusion of recombinant rat interleukin 4 also elicited significant intestinal uptake of 125I-IgE. We also present evidence for the presence of CD23 on rat intraepithelial lymphocytes. These data provide evidence for a novel, inducible, intestine-specific IgE uptake and transport mechanism.

Human B cell precursors proliferate and express CD23 after CD40 ligation.

The CD40 surface membrane molecule plays an important role in the activation of mature human B cells, but its role in earlier stages of B lineage development is unknown. Here, we have investigated the effects of triggering the CD40 antigen on B cell precursors (BCP) by crosslinking with anti-CD40 antibody presented by Fc gamma-receptor type II-transfected murine Ltk- cells (CD40 system). CD10+ surface immunoglobulin negative (sIg-) BCP, freshly isolated from fetal bone marrow or precultured on stromal cells, proliferated in the CD40 system. This effect required the presence of IL-3, which acted as a specific cosignal among a panel of cytokines examined. The association of IL-10 and IL-7 potentiated the observed IL-3 and CD40-dependent BCP proliferation, demonstrating that IL-10 can act on early B lineage cells. CD40-dependent activation of fetal BCP did not favor maturation to sIg+ B cells, but resulted in the induction of high levels of surface membrane CD23. The emerging CD23+ BCP lacked sIg and CD10, and represented an important proportion of the cycling cells in the CD40-dependent cultures. Taken together, our data demonstrate that stimulation of the CD40 antigen induces expression of the CD23 gene, and regulates cell proliferation during normal human B cell ontogeny.

Role of appendix in the development of inflammatory bowel disease in TCR-alpha mutant mice.

T cell receptor-alpha mutant mice (TCR-alpha-/-), created by gene targeting of the TCR-alpha gene in embryonic stem cells, spontaneously develop inflammatory bowel disease (IBD) resembling human ulcerative colitis. Since gut-associated lymphoid tissue is likely to play an important role in the development of chronic intestinal inflammation, we examined the changes in the appendix lymphoid follicle (ALF) and Peyer's patches (PP) in these mice. We found the structure of the ALF to be remarkably similar to that of the PP in the small intestine; in both instances, lymphoid follicles covered by surface epithelium (dome-formation) were found. The amount of proliferation in the lymphoid follicles of the appendix estimated by in vivo incorporation of 5-bromo-2'deoxyuridine was more than two times that of PP in TCR-alpha-/- mice. ELISPOT assay showed an increase of IgA, IgG1, and IgG2a, but not IgM-secreting B cells in ALF of TCR-alpha-/- mice compared to TCR-alpha+/- control mice. Furthermore, TCR-alpha-/- mice revealed an increase of autoantibody-producing B cells against the cytoskeletal protein tropomyosin in ALF as compared to PP. When TCR-alpha-/- mice underwent appendectomy at a young age (3-5 wk), the number of mesenteric lymph nodes cells at 6-7 mo were markedly less than in the sham-operated TCR-alpha-/- mice. Furthermore, appendectomy at 1 mo of age suppressed the development of IBD, with only 3.3% of these mice developing IBD in the 6-7-mo period of observation. In contrast, approximately 80% of controls, including the sham-operated TCR-alpha-/- mice, developed IBD during this period. These results suggest that ALF, rather than PP, is the priming site of cells involved in the disease process and plays an important role in the development of IBD in TCR-alpha-/- mice.