scholarly journals CD69 is expressed on platelets and mediates platelet activation and aggregation.

1990 ◽  
Vol 172 (3) ◽  
pp. 701-707 ◽  
Author(s):  
R Testi ◽  
F Pulcinelli ◽  
L Frati ◽  
P P Gazzaniga ◽  
A Santoni
Keyword(s):  
Platelet Activation ◽  
T Cell Activation ◽  
Cell Activation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Lymphoid Cells ◽  
General Role ◽  
Dose Dependent Fashion

CD69, a surface dimer so far considered an early activation antigen restricted to lymphocytes, was found constitutively expressed on human platelets. Biochemical analysis revealed that platelet CD69 appears on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a broad 55-65-kD band, in which three 55-, 60-, and 65-kD components were detectable when nonreduced, and as two 28- and 32-kD bands when reduced, corresponding to the two disulfide-linked chains of the dimer. It therefore closely resembles lymphoid CD69, although the resolution of the three bands under nonreducing conditions is not usually seen in lymphoid cells. Moreover, as CD69 expressed on activated lymphocytes and CD3bright thymocytes, both chains are constitutively phosphorylated. CD69 stimulation by anti-Leu-23 monoclonal antibodies induced platelet aggregation in a dose-dependent fashion. This effect was associated with Ca2+ influx and platelet degranulation, as revealed by adenosine triphosphate release. In addition, CD69 stimulation in platelets induced production of thromboxane B2 and PGE2, suggesting activation of arachidonic acid metabolism by cycloxygenase. As observed for CD69-mediated T cell activation, platelet activation through CD69 requires molecular crosslinking. These results suggest that CD69 may function as an activating molecule on platelets, as on lymphocytes, and point toward a more general role of this surface dimer in signal transduction.

Calpain Functions in a Caspase-Independent Manner to Promote Apoptosis-Like Events During Platelet Activation

Blood ◽  
1999 ◽  
Vol 94 (5) ◽  
pp. 1683-1692 ◽  
Author(s):  
Beni B. Wolf ◽  
Joshua C. Goldstein ◽  
Henning R. Stennicke ◽  
Helen Beere ◽  
Gustavo P. Amarante-Mendes ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Platelet Activation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Calcium Ionophore ◽  
Phosphatidyl Serine ◽  
Human Platelets ◽  
Independent Manner ◽  
Calcium Dependent

Apoptosis and platelet activation share common morphological and biochemical features. Because caspases are essential mediators of apoptosis, we examined whether platelets contain these proteinases and use them during platelet activation. Human platelets contained caspase-9, caspase-3, and the caspase activators APAF-1 and cytochrome c as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Upon treatment with cytochrome c and dATP, platelet cytoplasmic extracts recapitulated apoptotic events, including sequential activation of procaspase-9 and procaspase-3 and subsequent proteolysis of caspase substrates. Calcium ionophore-stimulated platelets also recapitulated apoptotic events, including cell shrinkage, plasma membrane microvesiculation, phosphatidyl serine externalization, and proteolysis of procaspase-9, procaspase-3, gelsolin, and protein kinase C-δ. Strikingly, however, these events occurred without caspase activation or release of mitochondrial cytochrome c, suggesting a role for a noncaspase proteinase. Supporting this, inhibition of the calcium-dependent proteinase, calpain, prevented caspase proteolysis, ‘apoptotic’ substrate cleavage, and platelet microvesiculation. In vitro, purified calpain cleaved recombinant procaspase-9 and procaspase-3 without activating either caspase, confirming the inhibitor studies. These data implicate calpain as a potential regulator of caspases and suggest that calpain, not caspases, promotes apoptosis-like events during platelet activation.

scholarly journals Biochemical and Biological Characterization of the Protective Leishmania pifanoi Amastigote Antigen P-8

2001 ◽  
Vol 69 (11) ◽  
pp. 6776-6784 ◽  
Author(s):  
M. Colmenares ◽  
M. Tiemeyer ◽  
P. Kima ◽  
D. McMahon-Pratt
Keyword(s):  
T Cell Activation ◽  
Protective Immunity ◽  
Cell Activation ◽  
Biochemical Characterization ◽  
Cysteine Proteinase ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Biochemical Analyses

ABSTRACT The Leishmania pifanoi amastigote antigen P-8 has been previously shown to induce protective immunity in a murine model of cutaneous leishmaniasis (L. Soong, S. M. Duboise, P. Kima, and D. McMahon-Pratt, Infect. Immun. 63:3559–3566, 1995). As this antigen is of interest for further vaccine studies, the biochemical characterization of P-8 was undertaken. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western-blot analysis, and gel filtration chromatography revealed that P-8 antigen consisted of two proteoglycolipid complexes. The P-8 epitope is associated with theL. pifanoi amastigote-specific glycolipid components found in the two complexes. The P-8 complex 1 (P-8c1) consists of a 56-kDa serine metalloproteinase, apolipoprotein E (derived from fetal bovine serum), and amastigote-specific glycolipids. The P-8 complex 2 (P-8c2) consists of a 31-kDa cysteine proteinase associated with amastigote glycolipids. Biochemical analyses suggest that the P-8 antigenic glycolipids may be distinct from previously describedLeishmania glycolipids (glycosylinositolphospholipids and sphingoglycolipids). Protective immunity studies revealed that P-8c1 (serine metalloproteinase-glycolipid complex) confers comparable protection against infection as immunopurified P-8. The isolated P-8c2 (cysteine proteinase-glycolipid complex) does not provide significant protection, nor does stimulation with P-8c2 result in significant T-cell activation in P-8- or P-8c2-vaccinated mice. Consequently, the P-8c1 complex appears to be the immunodominant component of P-8.

Calpain Functions in a Caspase-Independent Manner to Promote Apoptosis-Like Events During Platelet Activation

Blood ◽  
1999 ◽  
Vol 94 (5) ◽  
pp. 1683-1692 ◽  
Author(s):  
Beni B. Wolf ◽  
Joshua C. Goldstein ◽  
Henning R. Stennicke ◽  
Helen Beere ◽  
Gustavo P. Amarante-Mendes ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Platelet Activation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Calcium Ionophore ◽  
Phosphatidyl Serine ◽  
Human Platelets ◽  
Independent Manner ◽  
Calcium Dependent

Abstract Apoptosis and platelet activation share common morphological and biochemical features. Because caspases are essential mediators of apoptosis, we examined whether platelets contain these proteinases and use them during platelet activation. Human platelets contained caspase-9, caspase-3, and the caspase activators APAF-1 and cytochrome c as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Upon treatment with cytochrome c and dATP, platelet cytoplasmic extracts recapitulated apoptotic events, including sequential activation of procaspase-9 and procaspase-3 and subsequent proteolysis of caspase substrates. Calcium ionophore-stimulated platelets also recapitulated apoptotic events, including cell shrinkage, plasma membrane microvesiculation, phosphatidyl serine externalization, and proteolysis of procaspase-9, procaspase-3, gelsolin, and protein kinase C-δ. Strikingly, however, these events occurred without caspase activation or release of mitochondrial cytochrome c, suggesting a role for a noncaspase proteinase. Supporting this, inhibition of the calcium-dependent proteinase, calpain, prevented caspase proteolysis, ‘apoptotic’ substrate cleavage, and platelet microvesiculation. In vitro, purified calpain cleaved recombinant procaspase-9 and procaspase-3 without activating either caspase, confirming the inhibitor studies. These data implicate calpain as a potential regulator of caspases and suggest that calpain, not caspases, promotes apoptosis-like events during platelet activation.

scholarly journals The mouse vitronectin receptor is a T cell activation antigen.

1991 ◽  
Vol 173 (2) ◽  
pp. 343-347 ◽  
Author(s):  
K Moulder ◽  
K Roberts ◽  
E M Shevach ◽  
J E Coligan
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Lymphoid Cells ◽  
Vitronectin Receptor ◽  
Cell Functions ◽  
Murine Homologue ◽  
Accessory Molecule ◽  
T Cell Lines ◽  
Activation Antigen

In this report, we demonstrate that the T cell activation antigen, recognized by monoclonal antibody H9.2B8, is the murine homologue of the vitronectin receptor (VNR) and, thereby, we provide initial evidence that VNR is expressed on lymphoid cells. VNR is expressed on a variety of T cell lines, tumors, and Con A-activated splenocytes, but not resting T cells, and is capable of binding to the extracellular matrix proteins fibronectin, fibrinogen, and vitronectin, via the tripeptide sequence RGD. There was no evidence of novel beta chains pairing with the VNR alpha chain, as has been demonstrated in some human cells. In view of recent studies demonstrating that this molecule functions as an accessory molecule in T cell activation, the VNR may play an important role in mouse T cell functions.

Abstract 647: Identification of Platelet Derived Growth Factors A, B, C and D Specific Role in Vascular Remodeling

2015 ◽  
Vol 35 (suppl_1) ◽  
Author(s):  
Maria Gonzalez Diez ◽  
Anton Razuvaev ◽  
Ulf Hedin ◽  
Anders Hamsten
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
Blood Vessel ◽  
Platelet Activation ◽  
T Cell Activation ◽  
Vascular Remodeling ◽  
Cell Activation ◽  
Opposite Effect ◽  
Specific Role ◽  
Biological Processes

Restenosis is a major complication after coronary angioplasty and stenting. The major cause of restenosis is neointimal hyperplasia, which results from an excessive proliferative response of vascular smooth muscle cells (VSMC) to mechanical injury. Platelet derived growth factor (PDGF) family members (A, B, C, D) are known to be related to vascular remodeling. However whether this role is specific for each one or overlapping remains to be elucidated. Aim: To assess the specific role of PDGF family members (A, B, C, D) in vascular remodeling after injury. Methods: We used an established model of balloon injury in rat carotid artery. The endothelium of the intima is mechanically removed. The animals (n=10/group) were sacrificed at different time points after injury (0-2-20 hours, 2-5-15 days, 6-12 weeks). mRNA from carotid arteries were isolated for gene expression studies using microarray gene expression. Results: PDGFs are differentially expressed in vascular remodeling (mRNA, A adj P val=3.28E-06, B adj P val=4.52E-8, C adj P val=5,91E-15, D adj P val=2,64E-18). Also the expression profile differs among them. We selected the genes highly correlated with each of the PDGFs (Spearman correlation, │rs >0.7│) and identified the most preeminent biological pathways associated to each one. PDGF-A positively correlates with program cell death. On the other hand, PDGF-B and C have some overlapping biological processes. There is positive correlation with blood vessel morphogenesis and angiogenesis (B), cell differentiation (B and C), DNA replication (B and C), antigen presentation and T-cell activation/differentiation (B and C). However, there is negative correlation with platelet activation (B) and cell adhesion (B and C). PDGF-D positively correlates with blood vessel morphogenesis and angiogenesis (like B) and cell differentiation (B, C), but is negatively correlated with T-cell activation/proliferation (opposite effect to B and C), apoptosis (opposite effect to A) and platelet activation (B). Conclusion: We identified specific biological processes for PDGF- A, B, C and D. Despite some overlapping, each one plays a specific role within vascular remodeling.

scholarly journals CD18 Antibody Application Blocks Unwanted Off-Target T Cell Activation Caused by Bispecific Antibodies

Cancers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 4596
Author(s):  
Joseph Kauer ◽  
Fabian Vogt ◽  
Ilona Hagelstein ◽  
Sebastian Hörner ◽  
Melanie Märklin ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Lymphoid Cells ◽  
Bispecific Antibodies ◽  
Target Cells ◽  
Cytokine Release ◽  
Life Threatening ◽  
Blocking Antibodies

T cell-recruiting bispecific antibodies (bsAbs) are successfully used for the treatment of cancer. However, effective treatment with bsAbs is so far hampered by severe side effects, i.e., potentially life-threatening cytokine release syndrome. Off-target T cell activation due to binding of bispecific CD3 antibodies to T cells in the absence of target cells may contribute to excessive cytokine release. We report here, in an in vitro setting, that off-target T cell activation is induced by bsAbs with high CD3 binding affinity and increased by endothelial- or lymphoid cells that act as stimulating bystander cells. Blocking antibodies directed against the adhesion molecules CD18/CD54 or CD2/CD58 markedly reduced this type of off-target T cell activation. CD18 blockade—in contrast to CD2—did not affect the therapeutic activity of various bsAbs. Since CD18 antibodies have been shown to be safely applicable in patients, blockade of this integrin holds promise as a potential target for the prevention of unwanted off-target T cell activation and allows the application of truly effective bsAb doses.

scholarly journals Glycoprotein V is not the thrombin activation receptor on human blood platelets

Blood ◽  
1986 ◽  
Vol 68 (3) ◽  
pp. 720-725 ◽  
Author(s):  
D Bienz ◽  
W Schnippering ◽  
KJ Clemetson
Keyword(s):  
Platelet Activation ◽  
Polyclonal Antibodies ◽  
Blood Platelets ◽  
Polyacrylamide Gel Electrophoresis ◽  
Human Platelets ◽  
Exchange Chromatography ◽  
Thrombin Activation ◽  
Strong Candidate ◽  
Triton X ◽  
Kinetics Of

Thrombin activation of platelets involves two receptors: glycoprotein Ib (GPIb), which affects the kinetics of the response; and, as a strong candidate for the second, essential receptor, GPV, a hydrophobic, 82-kd glycoprotein with an isoelectric point (pI) of pH 5.85 to 6.55. Whole platelets were treated with endogenous platelets calcium-activated proteases, yielding a major fragment, GPV8, with molecular weight (mol wt) of 79 kilodaltons (kd). The fragment was purified by affinity chromatography on wheat germ agglutinin followed by ion exchange chromatography on DEAE-Sephacel using first a 0 to 0.7-mol/L and then a 0 to 0.3-mol/L NaCl gradient. A rabbit was immunized with the purified GPV8 for preparation of polyclonal antibodies. Crossed immunoelectrophoresis and two-dimensional polyacrylamide gel electrophoresis (PAGE) electrophoretic blotting with the separate phases of a Triton X-114 phase partition of human platelets showed the characteristic pattern of GPV in the hydrophobic phase. During thrombin- induced platelet aggregation GPV is hydrolysed, releasing a fragment, GPVf1, to the supernatant. The fragment GPVf1 still contains a thrombin- binding site. Anti-GPV antibodies blocked GPV proteolysis, but did not inhibit platelet activation induced by thrombin. We conclude that proteolysis of GPV by thrombin is not essential for platelet activation.

scholarly journals Immunochemical characterization of the platelet-specific alloantigen Leka: a comparative study with the PlA1 alloantigen

Blood ◽  
1984 ◽  
Vol 64 (6) ◽  
pp. 1212-1219 ◽  
Author(s):  
N Kieffer ◽  
B Boizard ◽  
D Didry ◽  
JL Wautier ◽  
AT Nurden
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Human Platelets ◽  
Blue Staining ◽  
Igg Antibody ◽  
Immune Disorder ◽  
Immunochemical Characterization ◽  
Coomassie Blue Staining ◽  
Coomassie Blue

Abstract We report the immunochemical characterization of a new platelet- specific alloantigen detected using an IgG antibody isolated from the serum of a patient with posttransfusion purpura (PTP). In indirect immunoprecipitation experiments, the antibody, termed anti-Leka, predominantly precipitated glycoprotein (GP) IIb from Triton X-100 lysates of normal human platelets. In an immunoblot procedure, which involved the transfer of platelet polypeptides separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to nitrocellulose membrane, anti-Leka bound exclusively to GP IIb. Under identical conditions, four anti-PlA1 antibodies each reacted with GP IIIa. No binding of anti-Leka IgG occurred to Leka (-) platelets or to their separated polypeptides although GP IIb was normally detected by Coomassie blue staining. After electrophoresis of reduced platelet proteins, the Leka determinant was localized to the IIb alpha chain. Thus, unlike the PlA1 antigen, the Leka determinant was not destroyed by disulfide reduction. Analysis of platelets from a patient with Glanzmann's thrombasthenia revealed little or no binding in the GP IIb position. Anti-Leka permitted the identification of 76,000 and 60,000 dalton fragments of GP IIb retained by the platelet following chymotrypsin treatment. Our results further highlight the immunogenicity of the GP IIb-IIIa complex. They also suggest that antibodies against GP IIb can cause the thrombocytopenia observed in PTP and that anti-PlA1 antibodies do not account exclusively for the pathophysiology of this immune disorder.

scholarly journals Mechanisms of Innate Lymphoid Cell and Natural Killer T Cell Activation during Mucosal Inflammation

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
David Nau ◽  
Nora Altmayer ◽  
Jochen Mattner
Keyword(s):  
T Cell ◽  
Natural Killer ◽  
T Cell Activation ◽  
Cell Activation ◽  
Inflammatory Responses ◽  
Adaptive Immune System ◽  
Nkt Cells ◽  
Lymphoid Cells ◽  
Mucosal Inflammation ◽  
Natural Killer T

Mucosal surfaces in the airways and the gastrointestinal tract are critical for the interactions of the host with its environment. Due to their abundance at mucosal tissue sites and their powerful immunomodulatory capacities, the role of innate lymphoid cells (ILCs) and natural killer T (NKT) cells in the maintenance of mucosal tolerance has recently moved into the focus of attention. While NKT cells as well as ILCs utilize distinct transcription factors for their development and lineage diversification, both cell populations can be further divided into three polarized subpopulations reflecting the distinction into Th1, Th2, and Th17 cells in the adaptive immune system. While bystander activation through cytokines mediates the induction of ILC and NKT cell responses, NKT cells become activated also through the engagement of their canonical T cell receptors (TCRs) by (glyco)lipid antigens (cognate recognition) presented by the atypical MHC I like molecule CD1d on antigen presenting cells (APCs). As both innate lymphocyte populations influence inflammatory responses due to the explosive release of copious amounts of different cytokines, they might represent interesting targets for clinical intervention. Thus, we will provide an outlook on pathways that might be interesting to evaluate in this context.

Potent Anti-Cancer Activity of Anti-NTB-a Monoclonal Antibodies in Preclinical Leukemia and Lymphoma Models

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4975-4975
Author(s):  
Wouter Korver ◽  
Xiaoxian Zhao ◽  
Shweta Singh ◽  
Cecile Pardoux ◽  
Ishita Barman ◽  
...  
Keyword(s):  
B Lymphocytes ◽  
Cell Lines ◽  
T Cell Activation ◽  
Cell Activation ◽  
Therapeutic Potential ◽  
Surface Protein ◽  
Lymphocytic Leukemia ◽  
Lymphoid Cells ◽  
Complement Dependent Cytotoxicity ◽  
Promising Target

Abstract NTB-A is a CD2-related cell surface protein expressed on lymphoid cells including B-lymphocytes from Chronic Lymphocytic Leukemia (CLL) and lymphoma patients. We have generated a series of mAbs against NTB-A and assessed their therapeutic potential in preclinical models. Selected mAbs to NTB-A were further tested in functional Complement Dependent Cytotoxicity (CDC) and Antibody Dependent Cellular Cytotoxicty (ADCC) assays in cell lines and B lymphocytes freshly isolated from CLL and lymphoma patients. Potent cytotoxic activity was demonstrated against B cells isolated from CLL patients and B lymphoma cell lines. Chimeric anti-NTB-A mAbs demonstrated anti-tumor activity equal to rituximab against CA46 human lymphoma xenografts in nude mice at a low dose. In a chimpanzee safety study, a single dose of lead anti-NTB-A mAb 994.1 resulted in near-complete depletion of peripheral lymphocytes while having a minimal effect on T cell activation. Taken together, these results demonstrate NTB-A as a promising target with an acceptable safety profile for immunotherapy of leukemia and lymphomas.

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