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Biomedical subjects

M W Carr

Publications and source records attributed to M W Carr.

11 recordsLinked to original sources
PubMed1997

Contrasting responses to multiple chemotactic stimuli in transendothelial migration: heterologous desensitization in neutrophils and augmentation of migration in eosinophils.

At inflammatory sites in vivo, leukocytes may confront multiple, competing chemoattractive signals. We found significant differences between eosinophils and neutrophils in transendothelial chemotaxis to a chemoattractant diffusing from the lower chamber, when a chemoattractant that binds to another receptor is present at uniform concentration. The transendothelial migration of eosinophils to FMLP, C5a, RANTES, or MCP-3 was totally inhibited by the presence of the homologous chemoattractant, and only RANTES and MCP-3 showed mutual inhibition. C5a and to a lesser extent FMLP chemokinetically stimulated migration to RANTES and MCP-3, without stimulating random migration. Results with neutrophils contrasted. The presence of FMLP not only abrogated neutrophil transmigration to FMLP but also strongly decreased chemotaxis to C5a, IL-8, and Gro-alpha. Similarly, C5a inhibited neutrophil chemotaxis to IL-8 and Gro-alpha. IL-8 almost totally abrogated chemotaxis to Gro-alpha, but Gro-alpha only moderately inhibited chemotaxis to IL-8. Neither IL-8 nor Gro-alpha significantly inhibited transmigration to FMLP or C5a. Actin polymerization in eosinophils and neutrophils was desensitized by the same combinations of chemoattractants that desensitized chemotaxis. We conclude that eosinophils have at least three noninterfering receptor-signal transduction pathways for chemotaxis and actin polymerization. In contrast, the signaling pathways for FMLP, C5a, and IL-8/Gro-alpha in neutrophils are heterologously cross-desensitized, with a hierarchy of resistance to competing signals of FMLP > C5a > IL-8 > Gro-alpha, in agreement with previous results in neutrophils on the Ca2+-mobilizing response. These results may have important implications for the behavior of these cell types in inflammatory sites.

Actins↗
PubMed1996

The C-C chemokine MCP-1 differentially modulates the avidity of beta 1 and beta 2 integrins on T lymphocytes.

The ability of chemokines, particularly MCP-1, to induce integrin-dependent binding of T lymphocytes to endothelial adhesion molecules or extracellular matrix (ECM) components was examined. MCP-1 induced significant adhesion to fibronectin (FN) and to endothelial-secreted ECM but not to purified ICAM-1 or VCAM-1, or to activated endothelium. The MCP-1-induced binding of T lymphocytes to FN was rapid, dose dependent, and resulted from activation of both VLA-4 and VLA-5. Like MCP-1, the chemokines RANTES and MIP-1 beta induced T lymphocyte binding to FN, but not to ICAM-1. We suggest therefore, that these T lymphocyte chemokines may be most important, not in initiating integrin-dependent firm adhesion of T lymphocytes to the vascular wall, but rather, in subsequent adhesive interactions during migration into tissue.

CD18 Antigens↗
PubMed1995

Characterization of transendothelial chemotaxis of T lymphocytes.

We have adapted a chemotaxis assay using human umbilical vein endothelial cell (HUVEC) monolayers on microporous membranes for studying lymphocyte transendothelial chemotaxis in vitro. Supernatants of peripheral blood mononuclear cells stimulated with phytohemagglutinin (PHA) were identified as an excellent source of lymphocyte chemoattractant activity. The activity in PHA supernatant typically caused 2-6% of peripheral blood lymphocytes (PBL) to transmigrate compared to 0.1-0.3% to media control. Checkerboard analysis demonstrated that transmigration was directional and not attributable to random locomotion. Purified T lymphocytes also underwent transendothelial chemotaxis to PHA supernatant. Using monoclonal antibodies to several human adhesion receptors, we found that the interaction between LFA-1 and ICAM-1/ICAM-2 was more important for transendothelial lymphocyte chemotaxis than the interaction between VLA-4 and VCAM-1. A monoclonal antibody to the beta 1 integrin subunit inhibited chemotaxis more than antibodies to the VLA alpha 2, alpha 3, alpha 4, or alpha 5 subunits. The transendothelial assay was used to guide purification of the lymphocyte chemoattractant activity, which we reported previously to be monocyte chemoattractant protein-1 (MCP-1) (Carr et al., Proc. Natl. Acad. Sci. USA (1994) 91, 3652). The adhesion molecules required for chemotaxis to MCP-1 were similar to those with PHA supernatant. The use of HUVEC in the assay enhances the signal-to-background ratio of chemotaxis and provides a model that is physiologically relevant to lymphocyte emigration from the bloodstream into sites of inflammation.

Antibodies, Monoclonal↗
PubMed1995

C-C chemokines, but not the C-X-C chemokines interleukin-8 and interferon-gamma inducible protein-10, stimulate transendothelial chemotaxis of T lymphocytes.

Eight chemokines were tested for ability to elicit transendothelial chemotaxis of unstimulated peripheral blood T lymphocytes. The C-C chemokines monocyte chemotactic protein (MCP)-2, MCP-3, RANTES, macrophage inflammatory protein (MIP)-1 alpha, MIP-1 beta, and, as previously described, MCP-1 induced significant, dose-dependent transendothelial chemotaxis of CD3+ T lymphocytes. In contrast, the C-X-C chemokines interleukin-8 (IL-8) and interferon-gamma inducible protein-10 (IP-10) failed to induce transendothelial chemotaxis of CD3+ T lymphocytes or T lymphocyte subsets. RANTES, MIP-1 alpha, and MIP-1 beta induced significant transendothelial chemotaxis of CD4+, CD8+, and CD45R0+ T lymphocyte subsets. Phenotyping of mononuclear cells that underwent transendothelial migration to MCP-2, MCP-3, RANTES, or MIP-1 alpha showed both monocytes and activated (CD26 high), memory-type (CD45R0+) T cells. Both CD4+ and CD8+ T lymphocytes were recruited, but not natural killer cells or significant numbers of B cells. MCP-2 was the only C-C chemokine tested that attracted a significant number of naive-type (CD45RA+) T lymphocytes. In the absence of endothelium, IL-8 but not IP-10 promoted modest but significant chemotoxis of CD3+ T lymphocytes. Our data support the hypothesis that C-C, not the C-X-C chemokines IL-8 or IP-10, promote transendothelial chemotaxis of T lymphocytes.

CD3 Complex↗
PubMed1995

The integrin VLA-4 supports tethering and rolling in flow on VCAM-1.

Selectins have previously been shown to tether a flowing leukocyte to a vessel wall and mediate rolling. Here, we report that an intergrin, VLA-4, can also support tethering and rolling. Blood T lymphocytes and alpha 4 integrin-transfected cells can tether in shear flow, and then roll, through binding of the intergrin VLA-4 to purified VCAM-1 on the wall of a flow chamber. VLA-4 transfectants showed similar tethering and rolling on TNF-stimulated endothelium. Tethering efficiency, rolling velocity, and resistance to detachment are related to VCAM-1 density. Tethering and rolling did not occur on ICAM-1, fibronectin, or fibronectin fragments, and tethering did not require integrin activation or the presence of an alpha 4 cytoplasmic domain. Arrest of rolling cells on VCAM-1 occurred spontaneously, and/or was triggered by integrin activating agents Mn2+, phorbol ester, and mAb TS2/16. These agents, and the alpha 4 cytoplasmic domain, promoted increased resistance to detachment. Together the results show that VLA-4 is a versatile integrin that can mediate tethering, rolling, and firm arrest on VCAM-1.

Cell Adhesion↗
PubMed1994

Monocyte chemoattractant protein 1 acts as a T-lymphocyte chemoattractant.

We have utilized a transendothelial lymphocyte chemotaxis assay to identify and purify a lymphocyte chemoattractant in supernatants of mitogen-stimulated peripheral blood mononuclear cells. Amino acid sequence analysis revealed identity with monocyte chemoattractant protein 1 (MCP-1), a chemoattractant previously thought to be specific for monocytes. Recombinant MCP-1 is chemoattractive for purified T lymphocytes and for CD3+ lymphocytes in peripheral blood lymphocyte preparations. The T-cell response to MCP-1 is dose-dependent and chemotactic, rather than chemokinetic. Phenotyping of chemoattracted T lymphocytes shows they are an activated memory subset. The response to MCP-1 by T lymphocytes can be duplicated in the absence of an endothelial monolayer and the majority of T-lymphocyte chemotactic activity in mitogen-stimulated peripheral blood mononuclear cell supernatants can be neutralized by antibody to MCP-1. Thus, MCP-1 is the major lymphocyte chemoattractant secreted by mitogen-stimulated peripheral blood mononuclear cells and is capable of acting as a potent T-lymphocyte, as well as monocyte, chemoattractant. This may help explain why monocytes and T lymphocytes of the memory subset are always found together at sites of antigen-induced inflammation.

Amino Acid Sequence↗
PubMed1989

To treat or not to treat: the controversy of handicapped newborns.

When dealing with the prospects of treating, not treating, or delaying treatment for handicapped newborns, there is no room for error. Since that is an impossible premise, one must make the best possible treatment plan for the newborn. The parents and members of the health care team should be included in the decision making. Those involved must also remember that no decisions are final; if the infant's physical condition changes, the treatment plan may be reevaluated. Any errors must be made by promoting the best interests of the infant in question, by keeping the infant alive longer than necessary rather than providing a premature death. Never, under any circumstances, should an infant be starved, dehydrated, or outright killed; to do so is to violate the rights of the infant. The infant's rights to life without constant pain are also violated by the senseless prolongation of his life and the promotion of wrongful life through the excessive use of modern technology.

Persons with Disabilities↗