Forms and functions of CD44

CD44 signaling through focal adhesion kinase and its anti-apoptotic effect

Adhesion molecules can initiate intracellular signaling. Engagement of CD44 either by its natural ligand hyaluronan or a specific antibody on a cell line induced tyrosine phosphorylation and activation of focal adhesion kinase (FAK), which then associated with phosphatidylinositol 3-kinase (PI3K) and activated mitogen-activated protein kinase at its downstream. However, the introduction of dominant negative Rho into the cells inhibited the CD44-stimulated FAK phosphorylation. Cells expressing CD44 were significantly resistant to etoposide-induced apoptosis. This anti-apoptotic effect was cancelled by the inhibition of either Rho, FAK or PI3K. These results may indicate a signaling pathway from CD44 to mediate the resistance against drug-induced apoptosis in cancer cells.

Hyaluronan-CD44 interaction hampers migration of osteoclast-like cells by down-regulating MMP-9

Osteoclast (OC) precursors migrate to putative sites of bone resorption to form functionally active, multinucleated cells. The preOC FLG 29.1 cells, known to be capable of irreversibly differentiating into multinucleated OC-like cells, displayed several features of primary OCs, including expression of specific integrins and the hyaluronan (HA) receptor CD44. OC-like FLG 29.1 cells adhered to and extensively migrated through membranes coated with fibronectin, vitronectin, and laminins, but, although strongly binding to HA, totally failed to move on this substrate. Moreover, soluble HA strongly inhibited OC-like FLG 29.1 cell migration on the permissive matrix substrates, and this behavior was dependent on its engagement with CD44, as it was fully restored by function-blocking anti-CD44 antibodies. HA did not modulate the cell-substrate binding affinity/avidity nor the expression levels of the corresponding integrins. MMP-9 was the major secreted metalloproteinase used by OC-like FLG 29.1 cells for migration, because this process was strongly inhibited by both TIMP-1 and GM6001, as well as by MMP-9-specific antisense oligonucleotides. After HA binding to CD44, a strong down-regulation of MMP-9 mRNA and protein was detected. These findings highlight a novel role of the HA-CD44 interaction in the context of OC-like cell motility, suggesting that it may act as a stop signal for bone-resorbing cells.

Dissimilar invasive and metastatic behavior of vincristine and doxorubicin-resistant cell lines derived from a murine T cell lymphoid leukemia

Multidrug resistance (MDR) lines from a murine T-cell lymphoid leukemia were selected in increasing vincristine (VCR) or doxorubicin (DOX) concentrations. Surface markers were determined by flow cytometry in both resistant (LBR-V 160 and LBR-D 160) and sensitive (LBR-) cell lines. Results obtained revealed similar expression of CD25, CD24, CD8, CD4, C18 and CD44, while differences in binding to hyaluronic acid (HA) were found. LBR- and LBR-D 160 bound to HA only after phorbol ester (PMA) activation, while LBR-V160 failed to bind HA even after PMA treatment. Histopathological analysis disclosed that LBR-V160 was less invasive than LBR- and LBR-D160 cell lines. In vitro growth of cell lines analyzed by sulforhodamine-B uptake showed that doubling time for the three lines was 10.24 h (LBR-), 16.75 h (LBR-V160) and 16.29 h (LBR-D160). Mortality rate was determined after i.p. injection of 10(4) cells. Mice inoculated with LBR- died at 23 2.11) days, while those inoculated with LBR-V160 or LBR-D160 died at 41 (+/- 9.53) or 41 (+/- 4.96) days, respectively. Our results demonstrated that leukemic murine T cells cultured in the long-term presence of VCR or DOX not only presented changes in the resistance phenotype but also variations in their growth and metastatic pattern.

Expression of CD44v5 and -v6 in Barrett's carcinoma is not increased compared to that in nondysplastic Barrett's mucosa

Barrett's adenocarcinoma currently shows the highest increase in the incidence of all malignant tumors. Reliable molecular markers to identify Barrett's patients at risk are still missing. Our own results demonstrate that the expression of CD44v6 correlates with the development of dysplasia in colorectal neoplasms. Therefore, we examined the expression of CD44 variants v5 and v6 in normal esophageal mucosa, non-dysplastic Barrett's mucosa, and Barrett's carcinoma. mRNA from biopsy specimens of patients with Barrett's esophagus (n = 19) or Barrett's carcinoma (n = 15) and patients without esophageal diseases (controls; n = 9) were extracted and used as templates for cDNA synthesis. CD44 variants were detected by RT-PCR with primers hybridizing with CD44 sequences up- and downstream of variable exons. CD44v6 expression was found in 36 of 56 biopsy specimens (64%) of non-dysplastic Barrett's mucosa, in 100% of squamous epithelium, and in none of the gastric mucosa specimens. Eleven of 15 specimens (73%) of Barrett's carcinoma tested positive for v6 expression. The identification of v5 expression did not give additional information. There was no correlation between CD44v5 or -v6 expression and staging or grading of the tumors. Expression of CD44v5 and -v6 seems to be independent of the development of cancer in Barrett's mucosa.

Conceptus influences the distribution of uterine leukocytes during early porcine pregnancy

Pregnancy in humans and rodents is associated with dramatic changes in leukocyte populations within the uterus. In these species, recruitment of leukocytes, mostly natural killer (NK) lymphocytes, accompanies decidualization of endometrial stroma even in the absence of pregnancy. In the pig, a nondecidualizing species, the predominant lymphocytes in the pregnant uterus are T and/or NK cells, but their distribution relative to embryonic attachment sites has not been reported. The objective of this study was to compare the abundance of leukocytes in porcine endometrium in contact with trophoblast with that between attachment sites during the early postattachment period. Uteri were recovered on Days 15-17 (n = 4), 18 and 19 (n = 4), 21 and 22 (n = 5), and 25-27 (n = 2) of gestation and from cycling pigs during the luteal phase (Day 15; n = 3). Leukocytes were identified in uterus obtained at versus between attachment sites using an antibody reactive with all leukocytes (CD44). In all pregnant animals, leukocytes were diffusely scattered throughout the endometrial stroma but were rare or absent in the luminal epithelium. Leukocyte density was approximately 3-fold greater in endometrium in contact with conceptuses than in endometrium between attachment sites throughout the early postattachment period. Leukocyte density during the luteal phase was similar to that between attachment sites, suggesting that leukocyte recruitment was a localized response to the embryo. The ability of an individual porcine conceptus to recruit maternal leukocytes to the adjacent stroma may be a vital step in early placental development and embryo survival.

Alternative splicing: combinatorial output from the genome

Alternative splicing has emerged as a mechanism that can account for a large proportion of the disparity between the modest number of genes in the human genome and the much higher complexity of the expressed proteome. At least a third, and probably the majority, of human genes are alternatively spliced, and some genes can generate thousands of protein isoforms by complex alternative splicing events. Analysis of the transcriptome will therefore require the development of massively parallel technologies that are able to encompass the complexity arising from alternative splicing.

Hyaluronan increases glomerular cyclooxygenase-2 protein expression in a p38 MAP-kinase-dependent process

BACKGROUND

Accumulation of the matrix glycosaminoglycan hyaluronan occurs in many types of renal injury but could follow any provision of hyaluronan substrate to the kidney, for example, through widespread use of supplementary glucosamine in osteoarthritic conditions. Hyaluronan can increase cyclooxygenase-2 (COX-2) protein and prostaglandin production. This effect was characterized in rat renal glomeruli to determine the cellular mechanism of activation.

METHODS

Isolated glomeruli were treated with purified hyaluronan (molecular mass 2 x 105 D) for up to 24 hours.

RESULTS

An increase in cyclooxygenase capacity and COX-2 protein was shown to follow the activation of p38-mitogen-activated protein (MAP) kinase and to be inhibited by a specific pyridinyl imadazole inhibitor (SB 202190). Hyaluronan-induced activation of cytosolic phospholipase A2 also was shown to be a p38 MAP kinase effect in these preparations. Prostaglandin production was inhibited by COX-2-specific non-steroidal anti-inflammatory compounds (NS-398 and celecoxib) but, as shown for many non-steroidal anti-inflammatory drugs (NSAIDs), an increase in COX-2 protein accompanied this inhibition.

CONCLUSIONS

We propose that these findings have clinical relevance. Prostaglandins have a number of important intrarenal regulatory effects leading to some debate over renal function with the use of NSAIDs. Where hyaluronan is increased, p38 MAP-kinase-dependent provision of prostaglandin substrate, via activation of cytosolic phospholipase A2, and a concomitant increase in cyclooxygenase-2 protein would raise renal prostaglandin levels. While NSAID treatment can prevent a rise in prostaglandin levels, it needs to be maintained to avoid possible exacerbation of pro-inflammatory conditions due to increased COX-2 protein levels.

Interaction of CD44 with different forms of hyaluronic acid. Its role in adhesion and migration of tumor cells

Interaction between hyaluronic acid (HA) and CD44 has been considered a key event in tumor invasion and metastasis. HA is a linear, high molecular weight glycosaminoglycan in its native state, but fragmented low molecular forms are found at sites ofneoplastic or inflammatory infiltrates. Both high and low molecular weights HA are involved in diverse biological functions. In this study, we used two clonal variants of a T cell murine lymphoma designated LBLa and LBLc. These cell lines were found to differ in their in vivo and in vitro growth rates. LBLa grew faster and exhibited an enhanced invasive capacity as compared to LBLc. In contrast, cell lines did not differ in the expression of surface markers (CD8, CD24, CD25, CD44, and CD18), or in their capacity to bind HA. However, LBLa cells exhibited higher capacity to migrate to low molecular weight HA than did LBLc. Migration was mediated by CD44 since it was abrogated by anti-CD44 monoclonal antibody as well as by hyaluronidase. We suggest that interaction between CD44 and low molecular weight HA may trigger migration mechanisms in LBLa cells, thus contributing to enhanced invasive cell capacity.

Evaluation of natural killer cell recruitment to embryonic attachment sites during early porcine pregnancy

Specialized natural killer (NK) lymphocytes are a feature of the pregnant uterus in humans and rodents. Conceptus-mediated recruitment of uterine (u)NK cells in the pig was proposed based on evidence that elevated uNK activity was temporally associated with increased leukocyte density in endometrium underlying conceptuses. The objective of this study was to determine whether uNK cells were more abundant at embryonic attachment sites during the early postattachment period. Mononuclear leukocytes were isolated from endometrium at attachment sites versus between attachment sites, and expression of CD16, a marker for NK cells, was assessed by flow cytometry. CD16 binding was normalized to leukocyte numbers in each sample. CD16+ small lymphocytes were more frequent in uterus than in blood (41% +/- 2% versus 26% +/- 4%). Differences between pregnant and luteal phase uterus (43% +/- 2% versus 31% +/- 7%, respectively) were not statistically significant. In pregnant animals, CD16+ lymphocytes were slightly but significantly more abundant in uterus at attachment sites versus between attachment sites at Days 15-17, 21-22, and 25-28. Before normalization, CD16+ large, granular cells were more abundant at attachment sites versus between attachment sites; however, these differences were removed when data were normalized according to leukocyte numbers. Further characterization showed that the proportion of large granular leukocytes expressing CD8, reactive with NK cells and T cell subsets, was 2-fold higher in pregnant uterus than in maternal blood. These results raise the possibility that uNK cells resembling those in blood may be transformed into larger, more granulated forms in the uterine microenvironment.

CD44 variant exons in leukemia and lymphoma

CD44 is a cell surface glycoprotein expressed on different cell types that functions in lymphocyte activation and homing, extracellular matrix adhesion and cellular migration. CD44 is encoded by a single gene composed of at least 20 exons. The standard CD44 protein (CD44S or CD44H) is the hematopoietic form of CD44 in lymphoid cells. Variant isoforms (designated from v1 to v10) are formed by addition of new exons to the extracellular domain. High levels of CD44v6 expression has been observed in some tumors and are associated with metastatic spread. The aim of the present study was to investigate and evaluate expression of the CD44v6 and v6-containing variants as a possible marker in chronic myeloid leukemia and lymphoma by reverse transcription-polymerase chain reaction. CD44 exon v6 was detected in all patients and all individuals in the control group. CD44v6-v10 mRNA was observed in 25 patients but in none of the subjects in the control group. CD44v6/v9-10, CD44v6-v7, CD44v6/v10 transcripts were detected in 11, 6, and 2 patients, respectively. CD44v6-7/v9-10 transcripts were not observed in either the patients or the healthy individuals. We conclude that CD44v6-v10 expression may be associated with hematologic malignancies.

CD44 expression in human gliomas

BACKGROUND AND OBJECTIVES

Glioma invasiveness involves the attachment of tumor cells to the brain extracellular matrix, rich in hyaluronic acid (HA). CD44, the principal receptor for HA is found as a standard molecule (CD44s) or as variants (CD44v). We undertook a retrospective study to evaluate the expression pattern of CD44s, the isoforms CD44v3, v4/5 and v6 and to correlate their expression with clinical-anatomopathological parameters and survival rate.

METHODS

The expression of these molecules was evaluated immunohistochemically in 84 gliomas.

RESULTS

No expression of CD44v was detected in any tumors. CD44s staining of tumor cells was found in 70 of 84 (83.3%) of the gliomas. In 23 of 39 (59.0%) of the GBM more than the 70% of the cells were stained, while only 2 of 21 (9.5%) of LGA showed high expression. The association between CD44 and histological grade remained when the prognostic variables were considered in a multivariate analysis. Higher expression of CD44 was associated with worse overall survival rate; however, the Cox analysis indicated that survival was not associated with CD44.

CONCLUSIONS

Our results suggest that overexpression of CD44s could be relevant in determining the highly invasive behaviour of gliomas, though it does not behave as an independent prognostic factor for survival.

Identification of a hyaluronic acid (HA) binding domain in the PH-20 protein that may function in cell signaling

The macaque sperm surface protein PH-20 is a hyaluronidase, but it also interacts with hyaluronic acid (HA) to increase internal calcium ( [Ca(2+)](i) ) in the sperm cell. A region of the PH-20 molecule, termed Peptide 2 (aa 205-235), has amino acid charge homology with other HA binding proteins. The Peptide 2 sequence was synthesized and two recombinant PH-20 proteins were developed, one containing the Peptide 2 region (G3, aa 143-510) and one without it (E12, aa 291-510). On Western blots, affinity-purified anti-Peptide 2 IgG recognized the 64 kDa band corresponding to PH-20 in acrosome intact sperm and, under reducing conditions, recognized the whole 67 kDa PH-20 and the endoproteolyzed N-terminal fragment of PH-20. HA conjugated to a photoaffinity substrate specifically bound to sperm surface PH-20. Indirect immunofluorescence demonstrated that Fab fragments of anti-Peptide 2 IgG bound to the head of live sperm. Biotinylated HA was bound by Peptide 2 and by sperm extracts in a microplate binding assay, and this binding was inhibited by Fab fragments of anti-Peptide 2 IgG. Biotinylated HA bound to the G3 protein and this binding was inhibited by anti-Peptide 2 Fab, but HA did not bind to the E12 protein. Fab fragments of anti-Peptide 2 IgG inhibited the increase in [Ca(2+)](i) induced in macaque sperm by HA. Our results suggest that the Peptide 2 region of PH-20 is involved in binding HA, which results in the cell signaling events related to the elevation of [Ca(2+)](i) during sperm penetration of the cumulus.

Mesothelial cell-associated hyaluronic acid promotes adhesion of endometrial cells to mesothelium

OBJECTIVE

To evaluate the role of hyaluronic acid in the attachment of endometrial cells to mesothelium.

DESIGN

In vitro study of adhesion of endometrial stromal and epithelial cells to mesothelial cells.

SETTING

University medical center.

PATIENT(S)

Reproductive-age women without endometriosis undergoing surgery for benign conditions.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The effect of hyaluronidase treatment of mesothelial cells or endometrial cells on adhesion of (51)Cr labeled endometrial stromal and epithelial cells to monolayers of mesothelium was evaluated. The expression of CD44, the hyaluronate receptor, was evaluated by western blot.

RESULT(S)

Hyaluronidase pretreatment of mesothelial cells decreased the binding of endometrial stromal and epithelial cells to mesothelium by 39% (P< .02) and 31% (P< .03), respectively. There was no effect on endometrial cell binding to mesothelial cells or to collagen IV when the endometrial cells were pretreated with hyaluronidase. CD44 expression by endometrial stromal and epithelial cells was demonstrated by western blot.

CONCLUSIONS

This study demonstrates that mesothelial cell-associated hyaluronic acid is involved in attachment of endometrial stromal and endometrial epithelial cells to the mesothelium. We hypothesize that binding of hyaluronic acid by endometrial cells is involved in the pathogenesis of the early endometriotic lesion.

The distribution pattern of the hyaluronan receptor CD44 during human tooth development

The aim was to investigate the expression pattern of the major cell-surface hyaluronan receptor CD44, as there are no existing data on its presence or absence in human dental structures at different developmental stages. Immunohistochemical localization of CD44 was studied using a monoclonal antibody, H3, that specifically recognizes an epitope in the common backbone of all CD44 isoforms. The dental lamina displayed a strong CD44 signal; the external enamel epithelium was negative. In the coronal region of the tooth germ the presecretory ameloblasts showed an intense reaction whereas the less differentiated inner enamel epithelial cells showed no signal at the cervical loop where they meet the external enamel epithelium. In the stellate reticulum a moderate reaction was detected. The secretory ameloblasts and the stratum intermedium showed a strong cell-surface CD44 signal. A strong signal was also observed on the odontoblasts and their processes. In the pulp, close to the odontoblastic layer, weak labelling was seen in the walls of capillary vessels. The distribution of CD44 in the human tooth germ corresponds to that of hyaluronan in most locations, suggesting that during tooth development this transmembrane protein plays an important part in hyaluronan-mediated events.

Discriminatory immunohistochemical staining of urothelial carcinoma in situ and non-neoplastic urothelium: an analysis of cytokeratin 20, p53, and CD44 antigens

Distinction of urothelial carcinoma in situ (CIS) from reactive atypia on the basis of morphology alone may be difficult in some cases. Because this distinction is therapeutically and prognostically critical, we attempted to determine if an immunohistochemical panel would help in this differential diagnosis. The immunoprofile of 21 cases of CIS and 25 non-neoplastic urothelia (15 urothelial biopsies with reactive atypia from patients without a history of bladder cancer and 10 normal ureter sections from nephrectomies performed for renal cell carcinoma) was determined using antibodies against cytokeratin 20 (CK20), p53, and CD44 (standard isoform). In the normal urothelium CK20 showed patchy cytoplasmic immunoreactivity in only the superficial umbrella cell layer and CD44 stained only the basal cells. Nuclear immunoreactivity to p53 varied from negative to weak and patchy. Reactive urothelium also showed CK20 immunoreactivity in only the umbrella cell layer in all 15 cases, and p53 nuclear staining was predominantly negative with occasional weak positivity in the basal and parabasal intermediate cells. CD44 was overexpressed in the entire reactive urothelium in 9 cases (60%) or focally positive in intermediate cells in 6 cases (40%). In contrast, CIS showed intense CK20 and p53 positivity (81% and 57%, respectively) in the majority (>50%) of malignant cells. CD44 staining revealed residual basal cells with membranous reactivity in 44% of the cases of CIS; however, the neoplastic cells were immunonegative in all cases. At least one positive immunomarker (CK20 or p53) was abnormally expressed in all cases of CIS. Abnormal expression of CK20 (increased), p53 (increased), and CD44 (decreased) in urothelial CIS, and increased expression of CD44 in reactive atypia allows more confident distinction of urothelial CIS from non-neoplastic urothelial atypias. From a differential diagnosis perspective, use of a panel of all three antibodies with morphologic correlation would be essential.

Molecular cloning of rat NK target structure--the possibility of CD44 involvement in NK cell-mediated lysis

The nature of target molecules of natural killer (NK) cell-mediated lysis remains to be elucidated. As we previously reported, mAb 109 recognizes one of the tumor-associated antigens, designated as 109 antigen (Ag), expressed on the cell surface of rat fibrosarcomas W31 and W14, which are transformants of WFB (rat fetal fibroblast cell line) with H-ras oncogene. 109Ag was thought to be a target structure of NK cells since mAb 109 inhibited NK cell-mediated lysis against W31 and W14. Here, we demonstrate by molecular cloning that 109Ag is identical to rat CD44. Immunoprecipitation and immunoblotting studies also showed that mAb 109 and anti-rat CD44 mAb OX-50 recognize the same protein of W31 cell lysates with an 86 kDa molecular size. CD44 was suggested to be a target structure of NK cell-mediated lysis; however, rat CD44 cDNA transfection alone into CD44 null cell lines did not result in up-regulation of target cell susceptibility to NK cell-mediated lysis. Our results therefore indicated that CD44 may play a crucial role as one of the target structures in our rat fibrosarcoma system though the cell surface expression of CD44 alone does not affect NK susceptibility of the target cells.

Structural and functional diversity of blood group antigens

Biochemical and molecular genetic studies have revealed that blood group antigens are present on cell surface molecules of wide structural diversity, including carbohydrate epitopes on glycoproteins and/or glycolipids, and peptide antigens on proteins inserted within the membrane via single or multi-pass transmembrane domains, or via glycosylphosphatidylinositol linkages. These studies have also shown that some blood group antigens are carried by complexes consisting of several membrane components which may be lacking or severely deficient in rare blood group 'null' phenotypes. In addition, although all blood group antigens are serologically detectable on red blood cells (RBCs), most of them are also expressed in non-erythroid tissues, raising further questions on their physiological function under normal and pathological conditions. In addition to their structural diversity, blood group antigens also possess wide functional diversity, and can be schematically subdivided into five classes: i) transporters and channels; ii) receptors for ligands, viruses, bacteria and parasites; iii) adhesion molecules; iv) enzymes; and v) structural proteins. The purpose of this review is to summarize recent findings on these molecules, and in particular to illustrate the existing structure-function relationships.

Involvement of CD44 in cytoskeleton rearrangement and raft reorganization in T cells

T cell activation is accompanied by actin-mediated receptor clustering and reorganization of lipid rafts. It has been suggested that costimulatory molecules might be involved in these processes. We here provide evidence that engagement of the adhesion molecule CD44 initiates cytoskeletal rearrangement and membrane reorganization in T cells. Cross-linking of CD44 on a T helper line was accompanied by adhesion, spreading and actin bundle formation. These processes were energy dependent and required an intact actin and microtubule system. They involved the small GTPase Rac as evidenced by the absence of spreading in cells overexpressing a dominant negative form of Rac. The CD44 initiated reorganization of the cytoskeleton was associated with the recruitment of CD44 and the associated tyrosine phosphokinases p56(lck) and p59(fyn) into glycolipid enriched membrane microdomains (GEM). We interpret the data in the sense that CD44 functions as a costimulatory molecule in T cell activation by inducing actin cytoskeletal rearrangements and membrane protein and lipid reorganization including its association with GEMs. Due to the association of CD44 with lck and fyn this colocalization with the TCR allows an abundant provision of these kinases, which are essential to initiate the TCR signaling cascade.

Expression of CD44 isoforms in squamous cell carcinoma of the border of the tongue: A correlation with histological grade, pattern of stromal invasion, and cell differentiation

BACKGROUND AND OBJECTIVES

Oral squamous cell carcinoma is a frequent disease with reserved prognosis, where the routinely evaluated morphological features lack a major correlation with prognosis. In order to assess the potential value of the immunoexpression of CD44 isoforms v3, v4-5, and v6, we studied it in a series of 56 consecutive cases of squamous cell carcinomas of the border of the tongue.

METHODS

All the histological (World Health Organization grade, Bryne score, degree of keratinization, and pattern of stromal invasion) and immunohistochemistry (using monoclonal antibodies to CD44v) results were exclusively assessed at the deep invasion front of the neoplasms. Downregulation of CD44v was defined by focal or irregular staining of < 10% of the cells at the deep invasive front.

RESULTS

There was downregulation of CD44v3 in 37.5% of the cases, CD44v4-5 in 67.9%, and CD44v6 in 33.9%, occurring mostly in cases with low Bryne scores and graded as well-differentiated according to the WHO classification. Downregulation of CD44v was found to correlate with cell differentiation, tumor grade, and the pattern of neoplastic invasion.

CONCLUSIONS

Our findings in the present series point to the consideration that CD44v pattern and intensity of immunoexpression in the deep invasive front of squamous cell carcinoma of the tongue are mostly related to tumor grade, the features of stromal invasion, and to the presence of cervical lymph node metastases.

Prognostic value of hyaluronan expression in non-small-cell lung cancer: Increased stromal expression indicates unfavorable outcome in patients with adenocarcinoma

The prognostic value of hyaluronan (HA) was analyzed in a large number of patients (n = 261) with non-small-cell lung cancer (NSCLC) by staining archived tumor samples with a biotinylated HA-specific probe. The level of HA in the tumor cells and surrounding stroma was scored and compared with parallel CD44 stainings, clinicopathological factors and survival data. Adenocarcinomas were characterized by a low percentage of HA-positive cells with low staining intensity compared with squamous-cell and large-cell/anaplastic carcinomas. The HA signal in the peri-tumoral stroma was often higher than that in the uninvolved stroma in all subgroups of NSCLC. CD44 and HA associated with the cancer cells showed a strong positive correlation with each other. In the whole tumor material, dominated by squamous-cell carcinomas (n = 168), recurrences were more often found in cases showing a low percentage of cancer cell-associated HA. However, within the adenocarcinoma subgroup (n = 68), a high percentage of cell-associated HA was correlated with poor tumor differentiation. Also specific for the adenocarcinoma subgroup was the increased number of recurrences in cases with a strong stromal HA signal. In survival analysis of the whole material (n = 189), a low percentage of HA-positive cancer cells was associated with a shortened disease-free survival (DFS) together with stage and tumor type. However, in the subgroup of patients with adenocarcinoma (n = 49), a strong stromal signal for HA predicted poor DFS. The level of HA in the stroma of adenocarcinomas retained its prognostic value in Cox's multivariate analysis. These results indicate that the frequency and intensity of HA has a significant prognostic value in NSCLC, particularly when the histological subtypes are analyzed as separate entities.

Expression of CD44 and its variant isoform v3 has no prognostic value in gastric cancer

AIMS

To study the controversial role of transmembrane glycoprotein CD44 as a moderator of tumour spread and as a prognostic factor in gastric cancer.

METHODS AND RESULTS

The expression of all CD44 forms and that with exon v3 was assessed in 198 stage I-IV gastric adenocarcinomas using immunohistochemistry. CD44 expression was found in 72% and CD44v3 in 55% of the cases. The intensity of CD44 expression was associated with the level of invasion and with hyaluronan expression, while the frequency of CD44 positive cells was not significantly related to any of the clinical or histological features of the tumours. CD44v3 expression failed to show any association with the clinical or histological variables examined. Neither total CD44 nor CD44v3 expression affected survival. The most important prognostic factors in this cohort were the level of invasion, lymph node status, tumour size and vascular or perineural invasion.

CONCLUSIONS

Changes in CD44 or CD44v3 expression level do not predict tumour spread or patient survival in gastric cancer.

Relationship of cytokeratin 20 and CD44 protein expression with WHO/ISUP grade in pTa and pT1 papillary urothelial neoplasia

The aim of this study was to assess the relationship of immunoreactivity of cytokeratin 20 (CK20) and CD44 across the spectrum of urothelial neoplasia using the WHO/ISUP consensus classification. A total of 120 papillary urothelial pTa and pT1 tumors (8 papillomas, 8 neoplasms of low malignant potential, and 42 low-grade and 62 high-grade carcinomas) were immunostained by using CK20 and CD44 antibodies. The relationships of tumor grade, pathologic stage, recurrences, and progression in stage with CK20 and CD44 immunoreactivity were assessed. WHO/ISUP grade correlated with tumor stage (P < 0.005), recurrence (P = 0.02), and progression in stage (P = 0.031). Normal urothelium showed CK20 immunoreactivity restricted to a few umbrella cells. Expression of CD44 in normal urothelium was restricted to the basal cell layer. Loss of CD44 immunoreactivity and increasing CK20 positivity were significantly associated with increasing tumor grade and stage (P < 0.005). An inverse relationship was observed in the staining patterns of CK20 and CD44 within individual cases, as well as in the aggregate data, with 79.2% of tumors with CD44 loss showing CK20 positivity (P < 0.001). In conclusion, CK20 and CD44 immunoreactivity are significantly related to the WHO/ISUP grade and to each other, and our data suggest their potential combined utility in predicting biologic behavior in patients with papillary urothelial pTa and pT1 neoplasms.

MYCN-related suppression of functional CD44 expression enhances tumorigenic properties of human neuroblastoma cells

Highly malignant neuroblastoma tumors with MYCN amplification have been shown to downregulate the expression of the CD44 adhesion receptor. We have previously shown that MYCN amplified neuroblastoma cell lines either lack CD44 expression or express a nonfunctional, nonhyaluronic acid-binding CD44 receptor. By analysis of cells with manipulated expression of either CD44 or MYCN, we demonstrate that transfection of cells with a CD44 full-length cDNA construct produced a functional receptor in single copy MYCN cells and a nonfunctional CD44 receptor in MYCN amplified cells, similar to the CD44 receptor expressed by cells with enforced MYCN. Analysis of the in vivo growth properties of the transfectants revealed that the restoration of a functional CD44 receptor in nonamplified cells resulted in the suppression of in vivo cell growth, therefore linking the MYCN-related lack of hyaluronic acid-binding function of CD44 to the highly tumorigenic properties of a subset of neuroblastoma cells.

Reduced CD44 standard expression is associated with tumour recurrence and unfavourable outcome in differentiated thyroid carcinoma

CD44 was detected with an antibody recognizing all forms of CD44 (CD44 standard) and others specific for its v3 and v6 variant isoforms; their prognostic value was evaluated in 213 patients with differentiated thyroid carcinoma (DTC). The staining patterns of CD44 standard (s) and CD44v6 in tumour tissue were quite similar, 176 cases (83%) being highly positive for CD44s and 153 cases (72%) for CD44v6. Only 18 (9%) tumours showed high expression of CD44v3. Papillary carcinomas were significantly more often high expressors of CD44s and CD44v6 than follicular carcinomas (p<0.001 for both). Age older than 60 years, distant metastases, and advanced pTNM stage were related to loss of expression of CD44s (p<0.001, p=0.021, and p=0.003, respectively). Tumour recurrence and cancer-related mortality were related to the reduced level of CD44s (p=0.049 and p=0.042). CD44v3 did not associate with any of the clinicopathological factors. In univariate analysis, CD44s was the only significant prognostic factor for disease-free survival (p=0.0488). In multivariate analysis, CD44s and thyroglobulin level were significant prognostic factors for disease-free survival (p=0.040 and p<0.001, respectively). The reduced level of CD44s in DTC patients seems to be an independent prognostic factor for unfavourable disease outcome.

Increased protein synthesis after T cell activation in presence of cyclosporin A

BACKGROUND

The immunosuppressive drug, cyclosporin A (CsA), blocks immune responses by inhibiting the calcineurin-dependent dephosphorylation of the nuclear factor of activated T cells (NFAT). We have previously reported that T cells activated in presence of CsA exhibit particular properties. In our study, we have tested the hypothesis that T cells activated in presence of CsA display a differential pattern of gene expression.

METHODS

T lymphocytes were activated in vitro by Concanavalin A with or without CsA. The cells were: (1) pulsed with 35S-methionine to label the newly synthesized proteins that in turn were revealed by 2D-gel electrophoresis; (2) analyzed by flow cytometry for activation markers expression; and (3) examined by gel electrophoresis for early tyrosine phosphorylation events.

RESULTS

The proteomic patterns of T lymphocytes activated by Concanavalin A, with or without CsA, were compared. In keeping with the well-known effect of the immunosuppressor, many polypeptides were not found in its presence. Remarkably, several newly synthesized polypeptides were detected only when activation was carried out in presence of CsA. In addition, immunologically relevant proteins, such as CD44 and CD69, escape CsA-inhibitory action. Furthermore, CsA did not modify the early protein tyrosine phosphorylation events resulting from T cell triggering.

CONCLUSIONS

The present data show that the effect of CsA on protein synthesis is more complex than anticipated. Signaling provided by T cell activation and the blockade of the calcineurin-dependent pathway by CsA results in an altered program of gene expression.

Bacterial signals and cell responses during Shigella entry into epithelial cells

Shigella invades epithelial cells by inducing cytoskeletal reorganization localized at the site of bacterial-host cell interaction. During entry, the Shigella type III secretion apparatus allows the insertion of a pore that contains the IpaB and IpaC proteins into cell membranes. Insertion of this complex is thought to allow translocation of the carboxy-terminus moiety of IpaC, but also of other Shigella effectors, such as IpaA, into the cell cytosol. IpaC triggers actin polymerization and the formation of filopodial and lamellipodial extensions dependent on the Cdc42 and Rac GTPases. IpaA, on the other hand, binds to the focal adhesion protein vinculin and induces depolymerization of actin filaments. IpaA and the GTPase Rho are not required for actin polymerization at the site of bacterial contact with the cell membrane, but allow the transformation of the IpaC-induced extensions into a structure that is productive for bacterial entry. Rho is required for the recruitment at entry foci of ezrin, a cytoskeletal linker required for Shigella entry, and also of the Src tyrosine kinase. The Src tyrosine kinase activity, which is required for Shigella-induced actin polymerization, also appears to be involved in a negative regulatory loop that downregulates Rho at the site of entry.

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.

Decreased elastin deposition and high proliferation of fibroblasts from Costello syndrome are related to functional deficiency in the 67-kD elastin-binding protein

Costello syndrome is characterized by mental retardation, loose skin, coarse face, skeletal deformations, cardiomyopathy, and predisposition to numerous malignancies. The genetic origin of Costello syndrome has not yet been defined. Using immunohistochemistry and metabolic labeling with [3H]-valine, we have established that cultured skin fibroblasts obtained from patients with Costello syndrome did not assemble elastic fibers, despite an adequate synthesis of tropoelastin and normal deposition of the microfibrillar scaffold. We found that impaired production of elastic fibers by these fibroblasts is associated with a functional deficiency of the 67-kD elastin-binding protein (EBP), which is normally required to chaperone tropoelastin through the secretory pathways and to its extracellular assembly. Metabolic pulse labeling of the 67-kD EBP with radioactive serine and further chase of this tracer indicated that both normal fibroblasts and fibroblasts from patients with Costello syndrome initially synthesized comparable amounts of this protein; however, the fibroblasts from Costello syndrome patients quickly lost it into the conditioned media. Because the normal association between EBP and tropoelastin can be disrupted on contact with galactosugar-bearing moieties, and the fibroblasts from patients with Costello syndrome revealed an unusual accumulation of chondroitin sulfate-bearing proteoglycans (CD44 and biglycan), we postulate that a chondroitin sulfate may be responsible for shedding EBP from Costello cells and in turn for their impaired elastogenesis. This was further supported by the fact that exposure to chondroitinase ABC, an enzyme capable of chondroitin sulfate degradation, restored normal production of elastic fibers by fibroblasts from patients with Costello syndrome. We also present evidence that loss of EBP from fibroblasts of Costello syndrome patients is associated with an unusually high rate of cellular proliferation.

Blocking of CD44-hyaluronic acid interaction prolongs rat allograft survival

BACKGROUND

Lymphocyte activation and infiltration into a transplanted organ is an integral component of the rejection process. Graft infiltration of lymphocytes requires adhesion of leukocytes to the endothelium, diapedesis, and transmigration. One of several proteins involved in this process is CD44, which is known to interact with endothelial hyaluronan (HA). Blockade of cell-matrix and cell-cell interactions have been used extensively for modulation of immune responses and graft rejection. Based on these observations, we evaluated the effects of blocking CD44-HA interactions in a transplantation model.

METHODS

We used a low molecular weight hyaluronic acid formulation (LMWHA) for the treatment of rat renal and cardiac allograft recipients. LMWHA was administered intraperitoneally at 0.5-5 mg/kg for 5-10 days after transplantation with or without a subtherapeutic dose of cyclosporine.

RESULTS

LMWHA monotherapy prolonged allograft survival significantly, but only for a few days. In combination with low-dose cyclosporine, long-term survival of allografts was observed in some of recipients.

CONCLUSION

Further definition of the underlying mechanism of LMWHA therapy may provide a rationale for the development of novel, nontoxic, nonimmunogenic immunotherapies.

CD44 binds to the Shigella IpaB protein and participates in bacterial invasion of epithelial cells

Shigella entry into epithelial cells is characterized by a transient reorganization of the host cell cytoskeleton at the site of bacterial interaction with the cell membrane, which leads to bacterial engulfment in a macropinocytic process. Using affinity chromatography on HeLa cell extracts, we show here that the hyaluronan receptor CD44 associates with IpaB, a Shigella protein that is secreted upon cell contact. Overlay and solid-phase assays indicated that IpaB binds directly to the extracellular domain of CD44; binding is saturable and inhibitable, with a half-maximal inhibitory concentration of 175 nM. Immunoprecipitation experiments showed that IpaB associates with CD44 during Shigella entry. CD44 is recruited at bacterial entry sites and localizes at the plasma membrane of cellular extensions induced by Shigella. Pretreatment of cells with an anti-CD44 monoclonal antibody resulted in inhibition of Shigella-induced cytoskeletal reorganization, as well as inhibition of bacterial entry, whereas transfection of CD44 in cells that are deficient for CD44 results in increased bacterial binding to cells and internalization. The IpaB-CD44 interaction appears to be required for Shigella invasion by initiating the early steps of the entry process.

Expression of CD44 in kidney after acute ischemic injury in rats

De novo CD44 and ligand expression at wound margins accompanies cellular proliferation and migration that effect repair of injured mucosal and vascular endothelial tissues. To determine whether CD44 could play a role in recovery from acute ischemic renal injury, we characterized its renal expression and those of two of its ligands, hyaluronic acid and osteopontin. Although no expression is detectable in nonischemic kidneys, several mRNAs for CD44 are present within 1 day after injury. CD44 mRNA is expressed in proximal tubules undergoing repair. CD44 peptide is present in basal and lateral cell membranes. Hyaluronic acid is normally expressed in the interstitium of the renal papilla only. By 1 day postischemia, hyaluronic acid can be detected, in addition, in the interstitium surrounding regenerating tubules. Osteopontin, not normally expressed in the renal proximal tubule, is expressed in regenerating tubules by 3 days after induction of acute ischemic injury. Immunoreactive osteopontin peptide continues to be localized in those tubules still undergoing repair for as long as 7 days after the injury. Our data are consistent with a role for CD44-ligand interactions in the regenerating proximal tubule participating in the process of recovery after ischemic injury.

Serum levels of the soluble adhesion molecules in patients with malignant melanoma

The incidence of malignant melanoma has been steadily increasing over the past decades. CD 44 is a transmembrane glycoprotein which is implicated in a number of adhesive and migratory events. Downregulation of CD 44 is implicated in the metastatic process. P-Selectin is a member of the selectin family of cell surface molecules. The levels of P-Selectin in biological fluids may be elevated in subjects with a variety of pathological conditions. In malignant melanoma, elevation of the plasma level of soluble intercellular adhesion molecule-1 (sICAM-1) has been associated with a reduction in disease-free survival. This study was performed to investigate the differences in the serum concentrations of the adhesion molecules in patients with malignant melanoma. The study group consisted of 52 patients with malignant melanoma and 20 healthy subjects. No meaningful difference was observed for P-selectin and sICAM 1 levels. A statistically significant decrease was observed in the cancer patients for serum CD 44 levels.

Signal transduction via CD44: role of plasma membrane microdomains

CD44 is the principal cell surface receptor for extracellular matrix glycosaminoglycan hyaluronan. CD44-hyaluronan mediated cell adhesion is important in several pathophysiological processes such as inflammation and metastatic spread of cancer cells. It has been recently recognized that CD44 also functions as a signaling receptor in a variety of cell types. Cell stimulation by monoclonal anti-CD44 antibody or natural CD44 ligands activate several signaling pathways that culminate in cell proliferation, cytokine secretion, chemokine gene expression and cytolytic effector functions. One of the earliest signaling events following stimulation via CD44 is tyrosine phosphorylation of intracellular proteins substrates, and CD44 mediated cellular activation could be abolished by protein tyrosine kinase (PTK) inhibitors. The Src-family non-receptor PTKs such as Lck, Fyn, Lyn and Hck were shown to be coupled to CD44 via sphingolipid-rich microdomains (lipid rafts) of the plasma membrane. Studies on T cell receptor and IgE receptor mediated signaling in lymphocytes and mast cells have consolidated the notion that microdomains consist of signaling platforms where components of multiple signaling pathways are assembled. Co-isolation of CD44 with microdomains strongly suggests that CD44 generates cellular activation signals utilizing the signaling machinery of the plasma membrane microdomains.

Synthesis and shedding of hyaluronan from plasma membranes of human fibroblasts and metastatic and non-metastatic melanoma cells

The regulation of hyaluronan synthesis and shedding was analysed in human fibroblasts and in two melanoma cells that differed in the metastatic potential and proteolysis of the hyaluronan receptor CD44. Dissociation of nascent hyaluronan from plasma membranes isolated from fibroblasts by high salt concentrations led to activation of hyaluronan synthase. Hyaluronan synthesis was also enhanced in plasma membranes from fibroblasts that had been treated with hyaluronidase or trypsin. Hyaluronan oligosaccharides stimulated hyaluronan production in fibroblast cultures. These results indicated that nascent high-molecular-mass hyaluronan inhibited its own chain elongation, if it was retained in the vicinity of the synthase by cell-surface receptors. The results also indicated that increased hyaluronan synthesis and shedding correlated with proteolysis of CD44 on the melanoma cell lines, which has been observed by others.

Stimulation of serglycin and CD44 mRNA expression in endothelial cells exposed to TNF-alpha and IL-1alpha

Serglycin is a widely distributed proteoglycan, previously assumed to be hematopoietic cell specific. However, the results presented show that serglycin mRNA is expressed outside the hematopoietic cell system. High levels of serglycin mRNA were detected in endothelial cells and smooth muscle cells, whereas low levels were detected in skin fibroblasts. To further analyze the importance of serglycin in endothelial cells, the expression of serglycin mRNA was measured following activation of an endothelial cell line derived from human umbilical cord vein (HUV-EC-C), by the proinflammatory cytokines TNF-alpha and IL-1alpha. The level of serglycin mRNA increased in a time- and dose-dependent way. TNF-alpha (7 ng/ml) was the most potent inducer, increasing the level of serglycin mRNA 2.5 times after 24 h of stimulation. Serglycin has been shown to be a ligand for CD44, a membrane protein expressed in endothelial cells. Following stimulation of the endothelial cells, the level of CD44 mRNA also increased. Again, TNF-alpha (7 ng/ml) turned out to be the most potent inducer, increasing the level of CD44 mRNA 5.5 times after 24 h of stimulation. Both TNF-alpha and IL-1alpha stimulation of the endothelial cells resulted in an increase in the total incorporation of [(35)S]sulfate into macromolecules, which probably indicates an increase in the total production of proteoglycans. A stimulation of endothelial cells by proinflammatory agents resulted in an increase in both serglycin and CD44 mRNA expression, indicating that serglycin, as well as CD44, may participate in the inflammatory process of leukocyte migration.

Alterations in blood leucocyte adhesion molecule profiles in HIV-1 infection

CD4 and CD8 lymphocyte numbers in the gut lamina propria are grossly altered in HIV-1 infection, out of proportion to alterations in the circulation. Such alterations in lymphocyte counts in the tissues may be due to altered leucocyte migration from the blood. One factor affecting leucocyte migration is adhesion molecule expression. Levels of adhesion molecule expression on peripheral CD4 and CD8 lymphocytes, monocytes and neutrophils from HIV-1-infected (AIDS and non-AIDS) and low-risk control individuals were compared. CD11a, CD62L, CD44, CD49d and beta7 integrin expression were examined by FACS analysis of fresh whole blood. Significant alterations in adhesion molecule expression were detected in HIV infection. The most striking alterations were observed in the CD8 lymphocyte population. CD11a expression was increased and CD62L and CD44 decreased. The CD4 lymphocyte population followed a similar, though less striking, pattern of alteration in adhesion molecule expression. Neutrophils displayed significantly reduced expression of both CD11a and CD62L, but only after onset of AIDS. Monocytes from infected individuals without AIDS displayed a different pattern of altered adhesion molecule expression compared with individuals with AIDS. These findings suggest that in HIV infection, leucocyte functions, such as migration, which require adhesion molecules are abnormal.

The bronchial epithelium as a key regulator of airway inflammation and remodelling in asthma

While asthma is an inflammatory disorder of the airways involving mediator release from mast cells and eosinophils and orchestrated by T cells, inflammation alone is insufficient to explain the chronic nature of the disease and its progression. Evidence is presented that the epithelium is fundamentally disordered in chronic asthma manifest by increased fragility, and an altered phenotype to one that secretes mucus, mediators, cytokines, chemokines and growth factors. Epithelial injury is mediated by exogenous factors such as air pollutants, viruses and allergens as well as by endogenous factors including the release of proteolytic enzymes from mast cells (tryptase, chymase) and eosinophils (MMP-9). Following injury, the normal epithelium should respond with increased proliferation driven by ligands acting on epidermal growth factor (EGF) receptors or through transactivation of the receptor. The epithelial response to these stimuli in asthma appears to be impaired despite upregulation of CD44 capable of enhancing presentation of EGF ligands to epidermal growth factor receptors (EGFR). Because the epithelium is 'held' in this repair phenotype, it becomes a continuous source of proinflammatory products as well as growth factors that drive airway wall remodelling.

Immunomodulatory functions of low-molecular weight hyaluronate in an acute rat renal allograft rejection model

Low molecular weight hyaluronate (LMW-HA) blocks interactions between T lymphocyte CD44 and hyaluronate (HA), a heteropolysaccharide that is expressed on the surface of endothelial cells and ubiquitously in the extracellular matrix. This study was undertaken to assess the ability of LMW-HA to modify the course of experimental acute renal allograft rejection. Lewis (LEW) rats were bilaterally nephrectomized and received an orthotopic, fully MHC-mismatched, Wistar-Furth (WF) kidney transplant. Animals received either no treatment, low doses of cyclosporin A (CsA) on days 0 to 5, LMW-HA on days 0 to 5, or CsA plus LMW-HA on days 0 to 5 after transplantation. With no treatment, CsA monotherapy, or HA monotherapy, animals rejected their allografts at a median of 15, 13, and 7.5 d, respectively (P = NS). In contrast, combined CsA plus LMW-HA therapy prevented acute rejection and significantly prolonged graft survival (P = 0.008) to a median of 49.0 d. CsA/LMW-HA-treated grafts also demonstrated better preservation of renal function at day 30 (serum creatinine level, 1.38+/-0.8 mg/dl), compared with surviving animals treated with CsA alone (2.9+/-0.55 mg/dl, P<0.05). Histologic graft analysis of CsA/LMW-HA-treated animals at day 7 after transplantation showed minimal rejection and leukocyte infiltration, compared with all other groups. Intragraft gene expression analysis, using semiquantitative reverse transcription-PCR, at the same time point showed reductions of CD4, CD8, and interferon-gamma transcript levels in the combined-treatment group. This is the first study demonstrating the immunomodulatory functions of LMW-HA in vivo in the setting of organ transplantation. Defining the exact mechanisms that underlie this immunomodulation may provide the rationale to develop novel strategies for use in clinical transplantation.

CD3-mediated T cell activation is inhibited by anti-CD44 monoclonal antibodies directed to the hyaluronan-binding region

The CD44 molecule has been shown to play a role in T cell adhesion and activation. We have investigated the ability of five anti-CD44 monoclonal antibodies (MoAb) including 15C6, 18A3, BU75 (Ancell), J173 (Immunotech), and L178 (Becton Dickinson) to regulate T cell activation. Three MoAb: 15C6, BU75, and J173 were found to selectively inhibit DNA synthesis, interleukin-2 (IL-2) receptor expression, and G1-->S transition of the cell cycle in T cells stimulated with anti-CD3 MoAb. None of anti-CD44 MoAb had influence on T cell proliferation induced by IL-2 or phorbol 12-myristate 13-acetate plus ionomycin. Inhibition of the CD3 pathway by anti-CD44 MoAb occurred by binding of MoAb directly to T cells without the involvement of monocytes or Fc receptors. In addition, the inhibitory anti-CD44 MoAb clearly suppressed intracellular calcium mobilization in T cells stimulated with anti-CD3 MoAb. Interestingly, the ability of anti-CD44 MoAb to inhibit T cell activation was well correlated with their capability to block the binding of hyaluronan (HA) to CD44 molecules. These results suggest that anti-CD44 MoAb directed to HA-binding site could selectively inhibit CD3-mediated T cell activation. Furthermore, CD44-mediated inhibitory signals would be linked to the blocking of early CD3-mediated signal transduction.

Functional aspects of red cell antigens

Over 250 blood group determinants are known and most of these are located on integral red cell proteins and glycoproteins. The functions of some of these structures are known: Diego (band 3) is the red cell anion exchanger; Kidd, a urea transporter; Colton (aquaporin 1), a water channel; Cromer (DAF) and Knops (CRI), complement regulators; Diego (band 3) and Gerbich (glycophorin C/D) link the red cell membrane and the membrane skeleton. The Duffy glycoprotein is a chemokine receptor that may act as a scavenger for inflammatory mediators in the peripheral blood, but is also exploited as a receptor by Plasmodium vivax merozoites. The functions of some blood group antigens can be speculated upon because of structural similarity to proteins and glycoproteins of known function. For example, the Lutheran, LW, and Ok glycoproteins are members of the immunoglobulin superfamily of receptors and signal transducers, the Rh proteins and related glycoproteins show homology to ammonium transporters, and the Kell glycoprotein resembles a family of endopeptidases. Yet most blood groups systems contain null phenotypes associated with no apparent pathology. If these blood group antigens have important functions, other structures must be able to carry out those functions in their absence. Almost nothing is known of the biological significance of blood group polymorphism.

The role of integrins in immune-mediated diseases of the nervous system

Immune-mediated diseases of the CNS and PNS, such as multiple sclerosis and Guillain-Barré syndrome, respectively, constitute a major cause of transient and permanent neurological disability in the adult. The aetiology and pathogenesis of these disorders are only partially understood. On a cellular level, focal mononuclear-cell infiltration with demyelination and eventual axonal loss is a crucial pathogenetic event that leads to inflammation and subsequent dysfunction. Here, the evidence that integrins, a family of cell adhesion molecules, expressed on neural and immune cells might play a central role in immune cell recruitment to the CNS and PNS, and probably in tissue repair is reviewed. Distinct integrin expression patterns are observed in multiple sclerosis and Guillain-Barré syndrome. Therapeutic targeting of integrins has been very successful in the corresponding animal models and holds promise as a novel treatment strategy to combat human immune-mediated disorders of the nervous system.

Insights into the structure and function of membrane polypeptides carrying blood group antigens

In recent years, advances in biochemistry and molecular genetics have contributed to establishing the structure of the genes and proteins from most of the 23 blood group systems presently known. Current investigations are focusing on genetic polymorphism analysis, tissue-specific expression, biological properties and structure-function relationships. On the basis of this information, the blood group antigens were tentatively classified into five functional categories: (i) transporters and channels, (ii) receptors for exogenous ligands, viruses, bacteria and parasites, (iii) adhesion molecules, (iv) enzymes and, (v) structural proteins. This review will focus on selected blood groups systems (RH, JK, FY, LU, LW, KEL and XK) which are representative of these classes of molecules, in order to illustrate how these studies may bring new information on common and variant phenotypes and for understanding both the mechanisms of tissue specific expression and the potential function of these antigens, particularly those expressed in nonerythroid lineage.

[Blood groups and structure-activity relations]

In the recent years, advances in biochemistry and molecular genetics have contributed to establish the structure of the genes and proteins from most of the 23 blood group systems presently known. From these findings, five functional classes of molecules can be schematically distinguished: (i) transporters and channels, (ii) receptors for ligands, viruses, bacteria and parasites, (iii) adhesion molecules, (iv) enzymes, and (v) structural proteins. Recent advances on these molecules will be reviewed, particularly by illustrating available structure-function relationships.