ADAM17-dependent proteolysis of L-selectin promotes early clonal expansion of cytotoxic T cells

L-selectin on T-cells is best known as an adhesion molecule that supports recruitment of blood-borne naïve and central memory cells into lymph nodes. Proteolytic shedding of the ectodomain is thought to redirect activated T-cells from lymph nodes to sites of infection. However, we have shown that activated T-cells re-express L-selectin before lymph node egress and use L-selectin to locate to virus-infected tissues. Therefore, we considered other roles for L-selectin proteolysis during T cell activation. In this study, we used T cells expressing cleavable or non-cleavable L-selectin and determined the impact of L-selectin proteolysis on T cell activation in virus-infected mice. We confirm an essential and non-redundant role for ADAM17 in TCR-induced proteolysis of L-selectin in mouse and human T cells and show that L-selectin cleavage does not regulate T cell activation measured by CD69 or TCR internalisation. Following virus infection of mice, L-selectin proteolysis promoted early clonal expansion of cytotoxic T cells resulting in an 8-fold increase over T cells unable to cleave L-selectin. T cells unable to cleave L-selectin showed delayed proliferation in vitro which correlated with lower CD25 expression. Based on these results, we propose that ADAM17-dependent proteolysis of L-selectin should be considered a regulator of T-cell activation at sites of immune activity.

A Randomised Controlled Trial Comparing Fibreoptic-Guided Tracheal Intubation through Two Supraglottic Devices: Ambu® Auragain™ Laryngeal Mask and LMA® Fastrach™

The Ambu®AuraGain™ laryngeal mask (LM) (Ambu A/S, Ballerup, Denmark) is one of the few readily available second-generation supraglottic airway devices (SADs) that offer a conduit for fibreoptic-guided endotracheal intubation. We aimed to compare fibreoptic intubation through this device with the LMA® (laryngeal mask airway) Fastrach™ (Teleflex Medical, Co. Westmeath, Ireland), which has been a recommended dedicated rescue device for the management of the unanticipated difficult airway. This randomised controlled trial compared a previously described fibreoptic score in 116 patients with no known airway pathology, who had asleep fibreoptic endotracheal intubation via either the AuraGain LM or the LMA Fastrach. Time, ease and success rate of SAD and endotracheal tube (ETT) insertion and complications were recorded. The AuraGain LM demonstrated better laryngeal alignment with 29 out of 59 patients in the AuraGain LM (AG) group having a Grade 4 view (only vocal cords visible), compared to 20 out of 54 patients in the LMA Fastrach (FT) group (P=0.003). It allowed significantly quicker and easier ETT intubation when used as a conduit. The AuraGain LM was also quicker to insert compared to the Fastrach LMA. Similar rates of minor complications, such as sore throat and dysphonia occurred in both groups. Our study indicates that when used in patients with complete muscle relaxation and no known airway pathology, the AuraGain LM achieves better laryngeal alignment and quicker, easier and more successful fibreoptic-guided ETT intubation than the Fastrach LMA.

T lymphocyte rolling and recruitment into peripheral lymph nodes is regulated by a saturable density of L-selectin (CD62L)

L-selectin mediates tethering and rolling of lymphocytes in high endothelial venules (HEV) of lymph nodes (LN) and of leukocytes at inflammatory sites. We used transgenic mice expressing varying levels of wild-type or a non-cleavable mutant form of L-selectin on T cells to determine the relationship between L-selectin density, tethering and rolling, and migration into LN. T cells expressing supraphysiological levels of either wild-type or non-cleavable L-selectin showed rolling parameters similar to C57BL/6 T cells in hydrodynamic flow assays and during rolling in Peyer's patch HEV. In contrast, PMA- or antigen-activated T cells and L-selectin(+/-) T cells expressing subphysiological levels of L-selectin showed reduced numbers of rolling cells with increased rolling velocity. Short-term homing studies showed that elevated expression of L-selectin above physiological levels had no effect on T cell migration to LN; however, low L-selectin expression resulted in reduced T cell homing to LN. Thus, T lymphocyte migration into LN is regulated by the density of cell surface L-selectin. In addition, there is a saturable density of L-selectin required for optimal homing to PLN in C57BL/6 mice, the L-selectin level on circulating naive T cells promotes optimal homing, and increased expression above saturating levels promotes no further increase in T cell recruitment.

L-selectin shedding does not regulate constitutive T cell trafficking but controls the migration pathways of antigen-activated T lymphocytes

L-selectin mediates rolling of lymphocytes in high endothelial venules (HEVs) of peripheral lymph nodes (PLNs). Cross-linking of L-selectin causes proteolytic shedding of its ectodomain, the physiological significance of which is unknown. To determine whether L-selectin shedding regulates lymphocyte migration, a mutant form that resists shedding (LdDeltaP-selectin) was engineered. Transgenic mice expressing either LDeltaP or wild-type (WT) L-selectin on T cells were crossed with L-selectin knockout (KO) mice. The cellularity and subset composition of secondary lymphoid organs did not differ between LDeltaP and WT mice, however, they were different from C57BL/6. Plasma levels of soluble L-selectin in LDeltaP mice were reduced to <5% of WT and C57BL/6 mice. The rolling properties of T lymphocytes from LDeltaP and WT mice on immobilized L-selectin ligands were similar. Furthermore, similar numbers of LDeltaP and WT T lymphocytes were recruited from the bloodstream into PLNs in mice, although LDeltaP T cells transmigrated HEVs more slowly. WT, but not LDeltaP-selectin, underwent rapid, metalloproteinase-dependent shedding after TCR engagement, and LDeltaP T cells retained the capacity to enter PLNs from the bloodstream. These results suggest that the ability to shed L-selectin is not required for T cell recirculation and homing to PLNs. However, L-selectin shedding from antigen-activated T cells prevents reentry into PLNs.

Transendothelial migration of lymphocytes across high endothelial venules into lymph nodes is affected by metalloproteinases

The migration of lymphocytes from the bloodstream into lymph nodes (LNs) via high endothelial venules (HEVs) is a prerequisite for the detection of processed antigen on mature dendritic cells and the initiation of immune responses. The capture and arrest of lymphocytes from flowing blood is mediated by the multistep adhesion cascade, but the mechanisms that lymphocytes use to penetrate the endothelial lining and the basement membrane of HEVs are poorly understood. Matrix metalloproteinases (MMPs) control the metastatic spread of tumor cells by regulating the penetration blood vessel basement membranes. In this study, synthetic and natural inhibitors were used to determine the role of MMPs and MMP-related enzymes in regulating lymphocyte extravasation in mice. Mice were treated systemically with the hydroxamate-based MMP inhibitor Ro 31-9790 and plasma monitored for effective levels of Ro 31-9790, which block shedding of L-selectin. The total numbers of lymphocytes recruited into LNs were not altered, but L-selectin levels were higher in mice treated with Ro 31-9790. A reduced number of lymphocytes completed diapedesis and there was an increase in the number of lymphocytes in the endothelial cell lining, rather than the lumen or the basement membrane of HEVs. Lymphocyte migration and L-selectin expression in the spleen were not altered by Ro 31-9790 treatment. Two MMP inhibitors, TIMP1 and Ro 32-1541, did not block L-selectin shedding and had no effect on lymphocyte migration across HEVs. These results suggest that metalloproteinase activity is required for lymphocyte transmigration across HEVs into LNs and provide evidence for the concept that metalloproteinases are important players in some forms of transendothelial migration. (Blood. 2001;98:688-695)

Production of monoclonal antibodies against excretory-secretory products of adult male Onchocerca gibsoni

Nine monoclonal antibodies (mabs) have been produced against excretory-secretory products (ES) of adult male Onchocerca gibsoni. These mabs fail to interact with the highly cross-reactive phosphorylcholine (PC) group and with ES of the related rodent filarial parasites Acanthocheilonema viteae and Litomosoides carinii. Eight of the mabs are of the IgG isotype: 1 is an IgM. Three of the mabs, OGMES 4, 9, and 10, were each found by immunoprecipitation/SDS-PAGE analysis of [3H] leucine-labeled ES, to recognize a triplet of polypeptides of molecular weight 120, approximately 210, and approximately 260 kDa. No recognition was observed by any mab when [3H] glucosamine was employed as the radiolabel for ES. Western blotting employing [125I] as indicator system demonstrated that OGMES 7 recognized a molecule of 27 kDa, and OGMES 1, a molecule of approximately 210 kDa, albeit faintly. These mabs may be of value to researchers working on the isolation, characterization, and detection in the bloodstream of Onchocerca volvulus ES.

Metalloproteinase-mediated regulation of L-selectin levels on leucocytes

Leucocyte (L)-selectin can be proteolytically cleaved in the membrane proximal extracellular region to yield a soluble fragment that contains the functional lectin and epidermal growth factor domains. A variety of stimuli are known to stimulate L-selectin shedding including chemoattractants, phorbol esters, and L-selectin cross-linking; however, the enzymes that regulate L-selectin expression are not characterized. In this study we have used phorbol ester to stimulate endoproteolytic release of L-selectin and identified a major role for a cell surface metalloproteinase (L-selectin sheddase) in this process. The hydroxamic acid-based inhibitor of zinc-dependent matrix metalloproteinases Ro 31-9790 completely prevented shedding of cell surface L-selectin from leucocytes in mouse, rat, and man. L-selectin was susceptible to cleavage by known matrix metalloproteinases. Recombinant human fibroblast collagenase (MMP1) reduced the number of L-selectin-positive lymphocytes to a similar extent as phorbol ester activation, and stromelysin (MMP3) had a partial effect on L-selectin expression. Gelatinases A (MMP2) and B (MMP9) were without effect. Lymphocytes did not express fibroblast collagenase or stromelysin at the cell surface, and tissue inhibitor of metalloproteinases (TIMP) did not affect L-selectin levels. L-selectin sheddase was not detected in media harvested from phorbol ester-stimulated lymphocytes and was only able to cleave L-selectin in the cis but not the trans configuration. These results suggest that endoproteolytic release of L-selectin from the leucocyte surface is mediated by a metalloproteinase (L-selectin sheddase), which is distinguishable from known matrix metalloproteinases. Understanding the regulation of L-selectin sheddase will be critical for controlling leucocyte migration from the blood.

A B lymphocyte surface molecule mediating activation and protection from apoptosis via calcium channels

A rat mAb (NIM-R5) was prepared against a 42-kD B cell activation Ag (p42). The expression of p42 is increased upon activation. NIM-R5 induces an increase of intracellular Ca2+, due to influx from the exterior milieu via calcium channels. This stimulation does not prejudice further stimulation with anti-Ig, and thus p42 constitutes an activation signal independent of membrane Ig. The antibody induces increased expression of class II molecules on resting B lymphocytes and prepares the cells for "spreading" when interacted with immobilized anti-class II antibody. The antibody alone is weakly mitogenic and comitogenic with IL-4 on resting B cells. Of particular interest, NIM-R5 induces proliferation and rescue from apoptosis in B cells activated in vitro. In conclusion, NIM-R5 induces an Ig-independent activation and proliferation of resting and activated B cells. This antibody does not recognize other known B cell activation Ag such as CD23, CD40, or CD72. We therefore propose that the p42 Ag is a glycoprotein with an important role in the regulation of B lymphocyte activation and survival.

A B lymphocyte surface molecule mediating activation and protection from apoptosis via calcium channels

A rat mAb (NIM-R5) was prepared against a 42-kD B cell activation Ag (p42). The expression of p42 is increased upon activation. NIM-R5 induces an increase of intracellular Ca2+, due to influx from the exterior milieu via calcium channels. This stimulation does not prejudice further stimulation with anti-Ig, and thus p42 constitutes an activation signal independent of membrane Ig. The antibody induces increased expression of class II molecules on resting B lymphocytes and prepares the cells for "spreading" when interacted with immobilized anti-class II antibody. The antibody alone is weakly mitogenic and comitogenic with IL-4 on resting B cells. Of particular interest, NIM-R5 induces proliferation and rescue from apoptosis in B cells activated in vitro. In conclusion, NIM-R5 induces an Ig-independent activation and proliferation of resting and activated B cells. This antibody does not recognize other known B cell activation Ag such as CD23, CD40, or CD72. We therefore propose that the p42 Ag is a glycoprotein with an important role in the regulation of B lymphocyte activation and survival.

Relative expression of surface IgM, IgD and the Ig-associating alpha(mb-1) and beta(B-29) polypeptide chains

Membrane immunoglobulins are associated with a transmembrane disulphide-linked heterodimer composed of an alpha-chain (mb-1) and a beta-chain (B-29). The relative surface expression of all of the polypeptide chains comprising the Ig-alpha beta complex has been investigated using surface labelling coprecipitation analysis and two-colour flow cytometric analysis. The main conclusions are that mb-1 and B-29 are B-cell surface markers on immature and mature B cells, and that all components of the surface Ig-alpha beta complex are expressed in stoichiometrically equivalent amounts. Thus the complex was quantitatively precipitated from digitonin lysates of 125I-surface-labelled cells with anti-B-29, anti-mb-1 or anti-Ig. Secondly, by two-colour FACS analysis there was a proportionality between the relative amounts of cell surface mb-1 or B-29 and surface IgM or IgD, but not other B-cell markers (class II, B220, FcR gamma, FcR epsilon). Finally there was an insignificant number of B cells expressing membrane Ig without alpha- and beta-chains, and vice versa. Thus there appears to be a closely controlled relative synthesis and surface expression of all components of the B-cell receptor complex.

Studies on a 14-kilodalton surface protein of Onchocerca microfilariae

A 14-kDa antigen present on the surface of uterine microfilariae of Onchocerca spp. has been identified using monoclonal antibodies. The antigen was also found in skin microfilariae, but in a masked or cryptic form. A complementary DNA clone encoding the epitope recognised by one of the monoclonal antibodies was identified in a lambda gt11 library. Nucleotide sequencing revealed that the 233-bp cDNA fragment codes for the carboxy-terminus of the antigen. The deduced amino acid sequence consists of three hydrophobic domains with high potential for beta-sheet formation. The amino-terminal hydrophobic domain is followed by 4 positively charged residues (positions 22-25) which contribute to the rather basic character of the protein. Another interesting feature of the polypeptide is its richness in phenylalanine (12.7%). From the sequence information, a synthetic peptide was synthesised which was recognised by one of the monoclonal antibodies directed against the 14-kDa antigen and a small number of sera from patients with onchocerciasis. The relevance of this to vaccination is discussed.

Factors that may influence the prescribing habits of rheumatologists

Questionnaire replies were received from 86% of all members of the British Association for Rheumatology and Rehabilitation soliciting opinions regarding influences and attitudes to prescribing. The importance and quality of information sources for new drugs were assessed and the importance of various aspects of information considered to be necessary for inclusion in a data card were investigated. The results indicated the professional journals and independent sources such as the Prescribers Journal are highly thought of by Rheumatologists and that advertisements and 'popular' journals are less likely to be important in the transmission of awareness of a new drug. The most important aspects of information considered to be necessary for inclusion in a data card or information bulletin were adverse- or side-effects. Specific details of the drug formulation or presentation are considered to be of much less importance. Rheumatologists prefer to prescribe by generic name and are likely to use two or three drugs in the treatment of a patient.