Human mast cells express the hyaluronic-acid-binding isoform of CD44 and adhere to hyaluronic acid

CD44 is expressed in various isoforms on multiple cell lineages including those of hematopoietic origin and is believed in part to mediate cell adhesion to hyaluronic acid. Elevated levels of soluble CD44 (sCD44) have been identified in the serum of some patients with specific neoplasms. We thus sought to determine whether human mast cells express functional CD44 and whether sCD44 might be associated with systemic mast cell disease. Using a standard assay, CD34(+)-derived cultured human mast cells were first demonstrated to adhere to hyaluronic-acid-coated surfaces. Human mast cells were then found by flow cytometry to express CD44S, but not the v5, v6, v7, and v8 isoforms, and to shed CD44S following activation induced by PMA or aggregation of FcvarepsilonRI. However, CD44S was not found to be consistently elevated in serum obtained from patients with mastocytosis or individuals experiencing anaphylaxis. Thus, human cultured mast cells express and shed CD44S, which appears to mediate the attachment of these cells to hyaluronic acid.     

Differentiation of mesothelioma from adenocarcinoma in serous effusions: the role of hyaluronic acid and CD44 localization

Differentiating cells of mesothelial origin from adenocarcinoma (ACA) based on morphology alone can be a diagnostic challenge, especially in cytological specimens. Malignant mesothelioma (MM) is characterized by accumulation of abundant intracellular hyaluronic acid (HA), a feature that is not reported in ACA. The purpose of this study was to evaluate the significance of cellular HA using an HA-specific binding peptide (HABP) and the expression of its principal receptor, the standard CD44 molecule (CD44S). Archival paraffin-embedded cell blocks of serous fluids from 28 cases of reactive mesothelial cells, 14 cases of MM, 20 cases of metastatic ovarian carcinomas, 17 cases of metastatic breast carcinomas, 12 cases of metastatic lung ACA, and 12 cases of metastatic gastrointestinal ACA were stained with HA using a biotinylated HABP and CD44S. Positive staining was defined as droplet to diffuse cytoplasmic staining for HA and uniform membranous staining for CD44S. All MMs and 93% (26/28) of the benign mesothelial cells were positive for intracytoplasmic HA vs. none of ACAs. CD44S was expressed in 100% (28/28) of mesothelial hyperplesia, 86% (12/14) of MMs, 70% (14/20) of ovarian carcinomas, 29% (5/17) of breast carcinomas, 25% (3/12) of gastrointestinal ACAs, and 8% (1/12) of lung ACAs. In MM and reactive mesothelial cells, CD44S stained cell membranes diffusely with highlights on the villous surfaces and in ACA it was focal and confined to cell membranes. Immunostaining with HA is a reliable marker that can distinguish between cells of mesothelial origin (reactive mesothelial cells and MM) and ACA. The CD44S staining pattern of cells of mesothelial origin is of diagnostic significance. CD44 may prove useful in conjunction with other stains in the differential diagnosis of mesothelioma and ADA.     

人CD44的结构与功能

CD44是属于黏附因子家族的跨膜糖蛋白。它广泛表达于多种内皮细胞、间充质细胞、造血干细胞及中胚层来源的细胞和组织。其最初作用被描述为介导淋巴细胞归巢到外周淋巴组织;后来发现CD44蛋白在多种生理和病理过程中起到重要作用,如造血、免疫反应(淋巴细胞活化和归巢)、发育、创伤愈合、炎症和肿瘤等。本文旨在分析CD44结构与功能的关系,探讨其与癌症的相关性。     

Human ovarian tumour cells can bind hyaluronic acid via membrane CD44: a possible step in peritoneal metastasis

Our previous studies have suggested that the interaction between hyaluronic acid (HA) on peritoneal mesothelial cells and the membrane adhesion molecule, CD44, on ovarian tumour cells could be important in ovarian cancer metastasis. In order to study this further, adhesion of six ovarian tumour lines to HA coated on to a plastic surface was investigated. Four lines bound to the HA coat and two lines did not. The adhesive lines were those that expressed high amounts of CD44, but the degree of adhesion was not closely correlated with CD44 expression. The results suggested that different tumour lines had different affinities for HA. Treatment of the HA coat with hyaluronidase substantially reduced adhesion. Adhesion was also partially reduced if the tumour cells were preincubated with either soluble HA, or anti-CD44 antibodies directed against the HA binding region. An antibody against a non-HA binding region only slightly blocked adhesion at high antibody concentrations. Only the CD44H isoform was detected by immunoprecipitation on the tumour cells. These results suggest that ovarian tumour cells can attach to immobilised HA via CD44H on the cell membrane.     

Expression of hyaluronic acid and its receptors, CD44s and CD44v6, in normal, hyperplastic, and neoplastic endometrium

The interaction between epithelial tumor cells and their surrounding stroma is important in tumor progression and metastasis. This is accomplished through a number of transmembrane receptors that interact with stromal extracellular matrix molecules. One of these receptors, CD44, binds to extracellular matrix component hyaluronic acid (HA). The purpose of this study was to evaluate the significance of HA, CD44s, and CD44v6 in benign, hyperplastic, atypical, and malignant endometrial epithelia. Archival paraffin-embedded cell blocks from proliferative endometrium (n = 11), secretory endometrium (n = 12), simple hyperplasia (n = 13), complex hyperplasia without atypia (n = 9), complex hyperplasia with atypia (n = 17), and adenocarcinoma (n = 21) were stained for HA, CD44s, and CD44v6. HA was detected throughout the normal menstrual cycle but was more intense during the secretory phase. Only during the secretory phase was CD44s expressed in the stromal cells in 11 cases (92%), whereas CD44v6 was detected in glandular epithelium in 9 (75%). CD44s was expressed in the glandular epithelium in 2 (15%) cases of simple hyperplasia, 4 (44%) of complex hyperplasia without atypia, 14 (82%) of complex hyperplasia with atypia, and in 16 (76%) of adenocarcinoma. CD44v6 was expressed in the glandular epithelium in 1 (11%) case of complex hyperplasia without atypia, 17 (100%) cases of complex hyperplasia with atypia, and in 18 (86%) cases of adenocarcinoma, but in none of the cases of simple hyperplasia. The endometrial stromal cells expressed CD44v6 in 1 (8%) case of simple hyperplasia, 6 (67%) of complex hyperplasia without atypia, 8 (47%) of complex hyperplasia with atypia, and in 3 (14%) of adenocarcinoma. We concluded that in the normal menstrual cycle, the timing of peak staining of HA and CD44s in the stroma and the up-regulation of CD44v6 in secretory glands are coincident with the period in which the endometrium is most receptive to embryo implantation. HA is more abundant in the stroma adjacent to the tumor, suggesting that interactions between tumor cells and stromal HA promote tumorigenesis. With progression from hyperplasia and with increasing atypia to adenocarcinoma, levels of stromal HA, glandular CD44v6, and glandular and stromal CD44s all increase. Thus, HA and CD44 are both involved in the development and progression of endometrial cancer.     

CD44s-targeted treatment with monoclonal antibody blocks intracerebral invasion and growth of 9L gliosarcoma

Glioma invasiveness is a complex process involving recognition and attachment of tumor cells to particular extracellular matrix (ECM) molecules prior to migrating into proteolytically modified matrix and inducing angiogenesis. CD44 is a group of transmembrane adhesion molecules found on a wide variety of cells including gliomas that has been suggested as the principal mediator of migration/invasion. The aim of the present study was to demonstrate whether antibody specific for the standard form of CD44 (CD44s, 85–90 kDa) might prevent invasion, thus blocking growth of the 9L gliosarcoma in vivo. High expression of CD44s on the surface of 9L cells and brain tumors was demonstrated by immunochemistry. Fluorescence-activated cell sorting (FACS) demonstrated binding saturation of anti-CD44s monoclonal antibody (mAb) to the receptor at 1 g/5 × 10⁵ cells. Blocking of CD44s in vitro resulted in a dose-dependent progressive, up to 95% ± 2.5% detachment of 9L cells from ECM-coated culture surfaces. Blocking of CD44s in vivo resulted in significantly reduced 9L brain tumors (2.5% ± 0.4%) – measured as the quotient: tumor surface (mm²)/brain surface (mm²) × 100 – as compared to untreated (16.1% ± 2.2%) or sham-treated rats (16% ± 3.7% to 16.1% ± 3%). We conclude that CD44s-targeted treatment with specific mAb may be an effective means for preventing glioma progression.     

CD44 and hyaluronic acid regulate in vivo iNOS expression and metalloproteinase activity in murine air-pouch inflammation

Objective: To evaluate the effects of anti-CD44 IM7.8.1 antibody, HMW-HA and LMW-HA on leukocyte migration and adhesion, and the induction of proinflammatory mediators, in mouse air-pouch inflammation induced by zymosan.Methods: Leukocytes were obtained from zymosan-air pouches after the intra-pouch injection of anti-CD44 IM7.8.1, isotype control, HMW-HA, LMW-HA or PBS. TNF-, IL-1 and iNOS mRNA were estimated in leukocytes by semi-quantitative RT-PCR. Matrix metalloproteinases (MMPs) from exudates were evaluated by zymography and Western Blot. Adhesion and migration of leukocytes were evaluated in HA-coated plates and Boyden chambers respectively.Results: IM7.8.1 decreased iNOS mRNA levels and the activity of both MMP-9 and MMP-2 eight h after injection into zymosan air pouch while IM7.8.1, HMW-HA and LMW-HA had no effect on IL1- or TNF- mRNA levels. Leukocytes from air pouch adhered to and migrated in vitro against both HMW-HA and LMW-HA. LMW-HA increased the number of leukocytes in the air pouch and iNOS mRNA levels as compared to PBS injection. In contrast, HMW-HA decreased leukocyte count and reduced iNOS mRNA levels. Paradoxically, the activity of both MMP-9 and MMP-2 was increased by HMW-HA and decreased by LMW-HA.Conclusions: Both CD44 and HA can modulate leukocyte migration and induction of proinflammatory mediators in mouse zymosan air pouch inflammation. IM7.8.1 had consistent anti-inflammatory effects, reducing iNOS, MMP-9 and MMP-2. HMW-HA and LMW-HA were able to modulate both the induction of proinflammatory mediators and leukocyte count in the air pouch.Received 8 December 2003; returned for revision 29 January 2004; accepted by M. J. Parnham 18 May 2004This work was supported by University of Buenos Aires Grant B081-UBACYT to S.H. and CONICET Grant PEI 6377 to G.B.Dr. Cabrera and Dr. Blanco contributed equally to this work.     

CD44 binds a chondroitin sulfate proteoglycan, aggrecan

Here we report that CD44 binds a chondroitin sulfate (CS) proteoglycan, aggrecan, a major component of cartilage. Soluble CD44-IgG and CD44(+) cells bound to aggrecan from rat chondrosarcoma and bovine cartilage, immobilized on microtiter plates. In both cases, binding was blocked by a neutralizing anti-CD44 mAb or by the pretreatment of aggrecan with chondroitinase, but not hyaluronidase or keratanase, indicating that CD44 binds aggrecan in a manner dependent on CS side chains of aggrecan and that hyaluronic acid is not involved in the binding. Structural analysis showed that glycosaminoglycans of aggrecan from rat chondrosarcoma and bovine articular cartilage consist of mainly CS A and a mixture of CS A and C respectively. When immobilized on microtiter plates, both CS A and C bound CD44-IgG, and the reaction was specifically inhibited by an anti-CD44 mAb. In addition, aggrecan augmented apoptosis in cells expressing CD44-Fas chimeric molecules in synergy with a non-blocking anti-CD44 mAb IRAWB14.4, suggesting that CD44-aggrecan interaction can induce oligomerization of the chimeric molecules. These results suggest that aggrecan interacts with CD44 to mediate cell adhesion and to trigger oligomerization of CD44 molecules, which may lead to intracellular signaling.     

CD44 expression and hyaluronic acid binding of malignant glioma cells

The mechanisms leading to rapid invasive growth of malignant gliomas are poorly understood. Expression of the hyaluronic acid (HA) receptor CD44 and adhesion to HA are involved in invasive properties. Our previous studies have shown that malignant glioma cells are able to adhere to extracellular HA. Here we investigated expression of the hyaluronic acid receptor CD44 protein in five human (T98G, A172, U87MG, 86HG39, 85HG66) and two rat (C6, 9L) glioma cell lines. Influence of anti-CD44 antibody and hyaluronidase-preincubation on the HA-binding was determined using HA/BSA (bovine serum albumin)-coated culture plates. While all gliomas were highly positive for CD44 with no differences in the number of positive staining cells, median fluorescence intensity decreased as follows: C6>T98G>9L>85HG66> 86HG39>A172> U87MG. Using HA/BSA coated culture plates the relative levels of specific adhesion to HA were determined as T98G>A172>9L>86HG39>U87MG> 85HG66. C6 cells failed to bind HA specifically. Incubation with anti-human-CD44 MAb significantly decreased HA-adhesion of T98G, A172, 85HG66 and U87MG human glioma cells. However the binding capacity was completely blocked only in 85HG66 cells. The three other cell lines kept a specific HA-adhesion after saturation of the receptor. Hyaluronidase pretreatment markedly enhanced HA-adhesion of C6 and 9L rat glioma cells. These results suggest that (i) HA-adhesion of malignant glioma cells is mainly, but not only, mediated by CD44, (ii) expression of CD44 does not correspond with adhesion capacity and (iii) cell-bound glycosaminoglycans may influence glioma cell adhesion to extracellular HA.     

标准型白细胞分化抗原44（CD44s ）鼻息肉发病过程中作用的初步研究

目的：研究CD44s 在鼻息肉中的表达及与鼻息肉发病的关系。方法：收集鼻息肉组织20例、正常下鼻甲粘膜组织15例(对照组)。HE 染色观察组织中炎症细胞浸润和上皮细胞受损情况;免疫组织化学染色观察CD44s 和EGF 的表达。结果：①鼻息肉粘膜上皮细胞、血管内皮细胞和基质炎症细胞CD44s表达（0.24±0.07,0.28±0.05,0.36±0.08）较下鼻甲粘膜（0.11±0.02,0.13±0.03,0.22±0.04）显著升高(P＜　0.05）;②鼻息肉组织中血管内皮细胞CD44s 蛋白表达和浸润Eos数目正相关(r=0.56,P＜0.05）;③EGF 在鼻息肉上皮表达（0.22±0.05）高于下鼻甲粘膜上皮（0.08±0.02）,差异具有统计学意义(P＜0.05）。结论：促进炎症细胞浸润、上皮损伤修复及疝出固有层的上皮化过程中,CD44s 可能扮有重要的角色。     

Mouse B cell activation is inhibited by CD44 cross-linking

Lymphocyte activation and trafficking are indispensable to the immune system. CD44 is an adhesion molecule with known importance in T cell activation, lymphocyte trafficking, and tumor metastasis. Although CD44 has been shown to participate in the activation, rolling and adhesion, and homing of T cells, the role of CD44 on B cells is relatively unknown. The effects of CD44 cross-linking on murine B cell activation via CD40L was explored using the anti-CD44 mAbs RK3G9 and IM7. When immobilized on a plate, both RK3G9 and IM7 were found to strongly inhibit B cell proliferation and Ig production, especially at lower cell input concentrations. IgE inhibition was especially prominent. In contrast, soluble RK3G9 added to the B cell cultures had no effect. The inhibitory effect of anti-CD44 on B cell activation was not influenced by the addition of the anti-FcγRII, indicating that Fc cross-linking did not play a role in this inhibition. As Ig production requires several days for both B cell proliferation and differentiation to occur, the effects of delayed addition of immobilized anti-CD44 mAbs were studied, and the results indicated no inhibition after 96 hrs of culture. Finally, B cells were activated by either LPS or anti-IgM F(ab')₂. While LPS-induced B cell activation was inhibited by immobilized anti-CD44 mAbs, anti-IgM activation was refractory. Interestingly, addition of both anti-IgM and CD40L or LPS resulted in some modulation of the inhibitory activity. These results suggest that CD44 cross-linking could control polyclonal B cell activation by CD40L, but allow sIgM/CD40L activation to continue.     

The CD44/integrins interplay and the significance of receptor binding and re-presentation in the uptake of RGD-functionalized hyaluronic acid

We have studied the interplay between two endocytic receptors for a carrier structure bearing two complementary ligands. Hyaluronic acid (HA; three different molecular weights) was functionalized with an RGD-containing peptide; this ancillary ligand allows the macromolecule to bind to α_v integrins in addition to the classical HA internalization receptor (CD44). The uptake of HA-RGD and of native HA was assessed in a phagocytic cell model (J774.2 murine macrophages), studying the kinetics of internalization and its mechanistic details. Indications of a synergic binding to integrins and CD44 emerged for HA-RGD; possibly, a first binding to integrins allows for a pre-concentration of the macromolecule on the cell surface, which is then followed by its binding to CD44. The endocytic mechanism and kinetics appeared then dominated by CD44, which has a much slower turnover than integrins. In this study we have demonstrated that the knowledge of the rate-determining steps of the internalization of a carrier is necessary for assessing its performance. In this case, the presence of multiple ligands on a carrier was beneficial in some respect (e.g. in improved binding/targeting), but may not be sufficient to overcome penetration barriers that arise from slow receptor re-presentation.     

流体剪切力下 CD44-HA 介导的 MDA-MB-231细胞及 HL60 细胞的滚动黏附

目的 探究胞外基质中的透明质酸(hyaluronic acid, HA)如何调控血流中CD44⁺肿瘤细胞的黏附滚动行为。方法 采用平行平板流动腔装置,观察记录流场中MDA-MB-231细胞及HL60细胞在固定HA上的运动,提取细胞滚动黏附特征参数。结果 MDA-MB-231细胞在HA底板上的黏附受到HA浓度的正向调控,但不受HA分子量影响;与物理吸附相比,生物素-亲和素固定的HA可显著提高细胞的黏附比率。在30～50 mPa剪切力范围内,剪切力的增加加快了细胞的滚动速度,降低了细胞的黏附比率,但对细胞的栓缚时间影响不大。同样流场中,与MDA-MB-231细胞比较,CD44表达水平较低的HL60细胞在HA底板上的栓缚时间短、滚动速度快、黏附比率低(<1.5%)。结论 流体剪切力可能通过调节CD44-HA的结合速率而非解离速率来调控MDA-MB-231细胞的滚动速度;CD44-HA相互作用参与HL60细胞的初始黏附,但不起主要作用。研究结果为抗肿瘤药物的开发提供参考。     

GLIOMA INVASION IN VITRO IS MEDIATED BY CD44–HYALURONAN INTERACTIONS

Invasion is a clinically important problem contributing to mortality and morbidity in patients with gliomas, but the mechanism(s) by which glioma cells invade surrounding brain structures is poorly understood. Various experimental models have been used in attempts to elucidate the process of glioma invasion. An in vitro model which is increasingly being employed involves measurement of the rate of invasion of tumour cells through Matrigel^®—a complex mixture of extracellular matrix components derived from the Engelbroth–Holm–Swarm (EHS) sarcoma. This model has been used to examine the possibility that extracellular hyaluronan (HA) might facilitate the invasive behaviour of human glioma cells. The major component of Matrigel^® is laminin, with smaller amounts of collagen IV, heparan sulphate proteoglycans, entactin, and nidogen, but it lacks HA. In our experiments, we have incorporated HA into Matrigel^® and have measured its effect on the rate of invasion of human glioma cells in a modified Boyden chamber assay system. The incorporation of HA (50–800 mg/cm²) resulted in a dose-dependent increase in invasion. Invasion was enhanced by up to 70 per cent in comparison with HA-free Matrigel^®. Since CD44 is a major HA receptor expressed on gliomas, it might have a role in the HA-mediated facilitation of invasion. This was tested by blocking CD44 with specific antibody, which resulted in a 43 per cent reduction in invasion rate. We conclude that in an in vitro model system, HA enhances invasion of glioma cells and that the mechanism involves a CD44–HA interaction. © 1997 by John Wiley & Sons, Ltd.     

Epithelial hyaluronic acid and CD44v6 are mutually involved in invasion of colorectal adenocarcinomas and linked to patient prognosis

Desmoplastic stroma of colorectal adenocarcinomas contains a variety of extracellular matrix molecules, including hyaluronic acid (HA). Overexpression of the HA receptor CD44 and, in particular, its splicing variant CD44v6 has been described as a prognostic factor for patients with colorectal adenocarcinomas in some studies, but converse reports also exist. Our hypothesis is that these divergent results may be related to the fact that the function of CD44v6 depends on the HA content of cell-surrounding matrix. Therefore, we studied the expression of HA and CD44v6 in tissue samples of 145 patients suffering from colorectal adenocarcinomas using immunohistochemistry. Expression of HA was separately evaluated in tumor epithelium and stroma. We additionally examined the influence of HA on invasion and adhesion of colorectal adenocarcinoma cells in vitro. The results show that epithelial HA expression was not correlated with tumor stage but with lymph-node or distant metastasis. Patients with tumors expressing epithelial HA had a decreased overall survival (P=0.017) as well as tumors with coexpression of epithelial HA and CD44v6 (P=0.011). The latter issue remained an independent prognostic factor in multivariate analysis (relative risk 5.06; 95% confidence interval, 1.18–21.57; P=0.028). HA exclusively stimulated in vitro invasion of CD44v6-expressing cells. This stimulation was partly reversed by an anti-CD44v6 antibody. Our findings suggest that the adverse prognostic effect of CD44v6 in colorectal adenocarcinoma might be restricted to those tumors that have pericellular HA.     

Antibody-induced activation of the hyaluronan receptor function of CD44 requires multivalent binding by antibody

CD44 can function as a receptor for hyaluronan (HA). However, many cell lines and normal hematopoietic cells that express CD44 do not constitutively bind HA. A monoclonal antibody (mAb) specific for CD44 (IRAWB14) has been described previously which induces CD44-mediated binding of HA rapidly (seconds to minutes) in some cell lines and in normal murine T cells. Of 16 CD44-specific mAb tested in the present study, only 3 exhibited this activity. Monovalent Fab fragments were prepared from two IgG2a antibodies that induce HA binding (IRAWB 14 and IRAWB 26) and used to determine whether multivalent binding was required for induction of HA receptor function. Fab from both antibodies had a tendency to form multivalent aggregates. After addition of iodoacetamide to prevent further aggregation, multimeric and monovalent forms were separated by gel filtration. This made it possible to compare the inducing activity of monovalent and multivalent antibody fragments of identical composition in the absence of Fc determinants. Multimeric forms were very active at inducing binding of fluorescein-conjugated HA (Fl-HA). Monovalent Fab fragments of both antibodies had 20- to 50-fold lower binding activity than intact antibody or multimer. IRAWB 26 Fab monomers were completely inactive in the induction of HA-binding. The observed weak inducing activity of IRAWB 14 Fab monomer could be attributed to very low levels of contaminating multimer. Induction of HA binding could also be achieved by using anti-immunoglobulin to cross-link Fab monomers of IRAWB 26. Thus, multivalent binding was required for the activation of HA binding by CD44-specific antibody, suggesting that the distribution of CD44 molecules on the cell surface is important for HA receptor function. In kinetic studies, induction of HA receptor function occurred simultaneously with antibody binding at 0°C (ice water bath). Furthermore, antibody could induce HA binding in paraformaldehyde-fixed cells, which were permeable to propidium iodide and trypan blue, suggesting that intracellular signaling mechanisms were not involved in induction of receptor function. We conclude, therefore, that these CD44-specific antibodies are inducing HA binding by directly influencing the distribution of CD44 on the cell surface. The possibility of a concurrent change in CD44 conformation is not ruled out. We discuss possible mechanisms by which CD44 might be activated to bind HA in vivo.     

Differences between healthy hematopoietic progenitors and leukemia cells with respect to CD44 mediated rolling versus adherence behavior on hyaluronic acid coated surfaces

We previously demonstrated that leukemia cell lines expressing CD44 and hematopoietic progenitor cells (HPC) from umbilical cord blood (CB) showed rolling on hyaluronic acid (HA)-coated surfaces under physiological shear stress. In the present study, we quantitatively assessed the interaction of HPC derived from CB, mobilized peripheral blood (mPB) and bone marrow (BM) from healthy donors, as well as primary leukemia blasts from PB and BM of patients with acute myeloid leukemia (AML) with HA. We have demonstrated that HPC derived from healthy donors showed relative homogeneous rolling and adhesion to HA. In contrast, highly diverse behavioral patterns were found for leukemia blasts under identical conditions. The monoclonal CD44 antibody (clone BU52) abrogated the shear stress-induced rolling of HPC and leukemia blasts, confirming the significance of CD44 in this context. On the other hand, the immobile adhesion of leukemia blasts to the HA-coated surface was, in some cases, not or incompletely inhibited by BU52. The latter property was associated with non-responsiveness to induction chemotherapy and subsequently poor clinical outcome.     

非小细胞肺癌患者CD44及其变异体V6的测定

目的：探讨测定粘附分子CD44及其变异体V₆在非小细胞肺癌（non-smallcelllungcarcinoma, NSCLC）中的意义。方法：采用酶联免疫吸附试验检测血清中可溶性CD44S（sCD44S）和可溶性CD44V₆（sCD44V₆）含量;流式细胞术测定细胞表面CD44S、CD44V₆的表达。结果：NSCLC患者血清CD44S、CD44V₆水平明显高于肺良性疾病（P<0.05, P<0.01）。原发肺鳞癌（SCC）和腺癌（ADC）细胞的CD44S表达率明显高于对照组（P<0.01）;3组的CD44V₆表达率均低,差异无显著。NSCLC原发癌细胞表面CD44S、CD44V₆表达与其血清的可溶性含量之间均无相关性。结论：提示血清CD44S、CD44V₆水平可作为鉴别NSCLC和肺良性疾病的辅助指标。     

Mouse B Cell Activation is Inhibited by CD44 Cross-Linking

Lymphocyte activation and trafficking are indispensable to the immune system. CD44 is an adhesion molecule with known importance in T cell activation, lymphocyte trafficking, and tumor metastasis. Although CD44 has been shown to participate in the activation, rolling and adhesion, and homing of T cells, the role of CD44 on B cells is relatively unknown. The effects of CD44 cross-linking on murine B cell activation via CD40L was explored using the anti-CD44 mAbs RK3G9 and IM7. When immobilized on a plate, both RK3G9 and IM7 were found to strongly inhibit B cell proliferation and Ig production, especially at lower cell input concentrations. IgE inhibition was especially prominent. In contrast, soluble RK3G9 added to the B cell cultures had no effect. The inhibitory effect of anti-CD44 on B cell activation was not influenced by the addition of the anti-FcγRII, indicating that Fc cross-linking did not play a role in this inhibition. As Ig production requires several days for both B cell proliferation and differentiation to occur, the effects of delayed addition of immobilized anti-CD44 mAbs were studied, and the results indicated no inhibition after 96 hrs of culture. Finally, B cells were activated by either LPS or anti-IgM F(ab′)₂. While LPS-induced B cell activation was inhibited by immobilized anti-CD44 mAbs, anti-IgM activation was refractory. Interestingly, addition of both anti-IgM and CD40L or LPS resulted in some modulation of the inhibitory activity. These results suggest that CD44 cross-linking could control polyclonal B cell activation by CD40L, but allow sIgM/CD40L activation to continue.