The L-selectin (Leu8) molecule is associated with the TcR/CD3 receptor; fluorescence energy transfer measurements on live cells

Overview of laser microbeam applications as related to antibody targeting

This chapter reviews several techniques which combine the use of laser microbeams with antibodies to study molecular and cellular biology. An overview of the basic properties of lasers and their integration with microscopes and computers is provided. Biophysical applications, such as fluorescence recovery after photobleaching to measure molecular mobility and fluorescence resonance energy transfer to measure molecular distances, as well as ablative applications for the selective inactivation of proteins or the selective killing of cells are described. Other techniques, such as optical trapping, that do not rely on the interaction of the laser with the targeting antibody, are also discussed.

Requirement of L-selectin for gammadelta T lymphocyte activation and migration during allergic pleurisy: co-relation with eosinophil accumulation

Intra-thoracic antigenic challenge (ovalbumin, 12.5 microg/cavity) led to increased numbers of gammadelta T lymphocytes in pleural cavities, blood and thoracic lymph nodes in sensitized mice within 48 h. Part of these cells expressed CD62L, which increased on gammadelta T cell surfaces obtained from lymph nodes after ovalbumin (OVA) challenge. Selectin blockade by fucoidan pre-treatment (10 mg/kg, i.v.) impaired in vivo increase in CD25(+) and c-fos(+) gammadelta T cell numbers in lymph nodes, indicating a role for selectins on gammadelta T lymphocyte activation and proliferation. In vivo selectin blockade by fucoidan or alpha-CD62L mAb (200 microg/mice, i.p.) also inhibited OVA-induced gammadelta T cell accumulation in pleural cavities. Confirming the direct effect of CD62L on gammadelta T cell transmigration, the migration of i.v. adoptively-transferred CFSE-labeled gammadelta T lymphocytes into pleural cavities of challenged recipient mice was impaired by fucoidan ex vivo treatment. It is noteworthy that eosinophil influx was also impaired in those mice, indicating that reduced eosinophil migration by CD62L in vivo blockade depended on gammadelta T cell migration via CD62L molecules. Accordingly, pleural gammadelta T lymphocytes from fucoidan-treated mice presented reduced OVA-induced IL-5 and CCL11 production. Supporting these data, the depletion of Vgamma4 T lymphocytes, which are pulmonary gammadelta T cells, decreased OVA-induced eosinophil influx into allergic site. Such results demonstrate that CD62L is crucial for the activation of gammadelta T cells in lymph nodes, for their migration into inflamed tissue and for the modulation of eosinophil influx during allergic response.

Differential effects of hydroxamate inhibitors on PMA and ligand-induced L-Selectin down-modulation: role of membrane proximal and cytoplasmic domains

L-selectin is down-modulated from the cell surface in response to leukocyte activation or cross-linking with ligand mimetics such as anti-L-selectin antibodies or sulfatides. The down-modulation induced upon cellular activation with PMA is due to proteolytic shedding mediated by a cysteine metalloprotease, presumably the TNF-alpha converting enzyme (TALE), and is susceptible to inhibitors of the hydroxamate class. To determine if cross-linking-induced down-modulation of L-selectin is similarly affected by these inhibitors, we exposed Jurkat T cells to the anti-L-selectin antibody Dreg 200 or sulfatides in the presence of the hydroxamate TNF-alpha protease inhibitor (TAPI). TAPI completely inhibited PMA-induced downmodulation but had no effect on that induced by the anti-L-selectin antibody or sulfatides. The downmodulation induced by an anti-TCR antibody (WT31) was only partially inhibited by TAPI. An L-selectin mutant lacking the putative TACE cleavage site and resistant to PMA-induced shedding (321del.9) was expressed in L1.2 pre-B cells. Like WT L-selectin, this mutant was down-modulated when exposed to sulfatides, or Dreg 200 and this down-modulation was unaffected by TAPI. An L-selectin cytoplasmic tail deletion mutant (344del.15) expressed in L1.2 pre-B cells was down-modulated by PMA or sulfatides, but not Dreg 200. Electrophoretic analysis of L-selectin immunoprecipitated from the supernatants of Jurkat cells treated with either sulfatides or D200 revealed a proteolytic fragment of the same size as that released from the cell surface in response to PMA. Our data indicate that the down regulation of L-selectin in response to cross-linking by ligands or TCR engagement may be mechanistically distinct from that induced by PMA. Furthermore, our results with the 344del.15 mutant suggest that the down-modulation of Lselectin induced by certain sulfated carbohydrate ligands may be initiated through surface receptors other than L-selectin itself. The abbreviations used in this paper are: TAPI, TNF-alpha protease inhibitor; TACE, TNF-alpha converting enzyme; PMA, 4(3-phorbol 12-myristate 13-acetate.

Regulation of schistosome egg granuloma formation: host-soluble L-selectin enters tissue-trapped eggs and binds to carbohydrate antigens on surface membranes of miracidia

Immunogenic carbohydrate epitopes are prominent in soluble egg antigens (SEA) of Schistosoma mansoni and in vivo are released through ultramicroscopic pores in the eggshell. Previously, one immunogenic carbohydrate was identified as lacto-N-fucopentaose III (LNFPIII), which contains the biologically important trisaccharide Lewis(x) (Le(x)), a weak ligand for E-, L-, and P-selectins. Selectins are involved in various inflammatory reactions, including recruitment of granulocytes. Further, L-selectin molecules are shed from leukocyte cell surfaces upon activation. These independent observations suggest that selectins may play various roles in granuloma formation and/or regulation. We tested in situ for alterations in expression of host E-, L-, or P-selectin in murine liver tissue at various times postinfection with schistosome cercariae. We found that L-selectin was expressed on cells surrounding egg granulomas, but surprisingly we also found mouse L-selectin on the surface membranes of larval miracidia within the S. mansoni ova. In contrast, neither E- nor P-selectin was found within ova. Antibodies to human or rat L-selectin or 15 other distinct mouse leukocyte surface molecules did not bind to the miracidial surface. The anti-mouse L-selectin staining of miracidia could be inhibited by wash buffer containing sulfated carbohydrates such as sulfated Le(x), heparan sulfate, fucoidan, and carrageenan. The elution studies imply that the miracidial surface and, therefore, schistosomes express sulfated glycans. The binding of soluble L-selectin to miracidia was not restricted by the genetic background of the host, as mouse L-selectin was detected on the surface of S. mansoni miracidia in livers from BALB/C, CBA/J, C57BL/6, and outbred Swiss mice. We also detected soluble mouse L-selectin binding to Schistosoma japonicum miracidia, indicating that these observations can be generalized to all schistosome infections. On the basis of these observations we hypothesize that host-soluble L-selectin traverses through pores in the eggshell and binds to target ligands on the surface membranes of miracidia; this complex formation might ultimately impede the release of soluble antigens from the eggs. The intraovum binding of mouse L-selectin to immunogenic carbohydrate antigens is a novel role for selectins, and this model may, in part, explain the down-regulation in granulomatous pathology observed following the acute phase of the disease.