Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously developed a simple mathematical model describing Ag-triggered lymphokine release from activated T cells. Previous test of this model revealed qualitative differences in the antigenic requirement for lymphokine release between activated T cell populations with the same apparent specificity when activated under different conditions. We now have found a case where class I MHC-reactive T cells (class I T cells) can modulate the nature of Ag-triggered lymphokine release from class II MHC-reactive T cells (class II T cells). Two significant requirements for this modulation event are: 1) Linked recognition/presentation of class I and class II Ag; that is, class I and class II MHC alloantigens must be presented on the same APC, and 2) active participation of the APC in this process; metabolic inactivation of the APC abrogates the class I T cell modulation of the class II activated T cell. These results suggest a novel form of T-T collaboration that involves the active participation of the APC, and provides evidence that T cells of one MHC specificity (class I) can influence the function of T cells of another MHC specificity (class II).
J Immunol 1989 Dec 15
PMID:A quantitative analysis of lymphokine release from activated T cells. Evidence for a novel form of T-T collaboration in vitro. 251 46

The clinical and serological findings in 13 patients with myocardial infarction and antiphospholipid antibodies (the 'lupus anticoagulant', antibodies to cardiolipin, antibodies to phosphatidylethanolamine (one patient] seen by our unit and other units from 1984 to 1989, are presented (eight males and five females, ages ranging from 20 to 52 years). Five suffered myocardial infarction before the age of 30; four of these five were in their early 20s. Other risk factors such as excessive smoking (greater than 20 cigarettes a day) (two patients), long-term treatment with steroid (one) and use of oral contraceptives (one) were present. One patient had demonstrated a plasminogen activator deficiency and one a deficiency of protein C. Two patients developed myocardial infarction six to eight weeks after warfarin was discontinued for recurrent deep vein thrombosis. Six patients had SLE as defined by the revised 1982 criteria, three suffered from 'lupus-like' disease, while four patients conformed to a 'primary' antiphospholipid syndrome.
Q J Med 1989 Dec
PMID:Myocardial infarction and antiphospholipid antibodies in SLE and related disorders. 251 55

A cytokine synthesis inhibitory factor (CSIF) is secreted by Th2 clones in response to Con A or antigen stimulation, but is absent in supernatants from Con A-induced Th1 clones. CSIF can inhibit the production of IL-2, IL-3, lymphotoxin (LT)/TNF, IFN-gamma, and granulocyte-macrophage CSF (GM-CSF) by Th1 cells responding to antigen and APC, but Th2 cytokine synthesis is not significantly affected. Transforming growth factor beta (TGF-beta) also inhibits IFN-gamma production, although less effectively than CSIF, whereas IL-2 and IL-4 partially antagonize the activity of CSIF. CSIF inhibition of cytokine synthesis is not complete, since early cytokine synthesis (before 8 h) is not significantly affected, whereas later synthesis is strongly inhibited. In the presence of CSIF, IFN-gamma mRNA levels are reduced slightly at 8, and strongly at 12 h after stimulation. Inhibition of cytokine expression by CSIF is not due to a general reduction in Th1 cell viability, since actin mRNA levels were not reduced, and proliferation of antigen-stimulated cells in response to IL-2, was unaffected. Biochemical characterization, mAbs, and recombinant or purified cytokines showed that CSIF is distinct from IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IFN-gamma, GM-CSF, TGF-beta, TNF, LT, and P40. The potential role of CSIF in crossregulation of Th1 and Th2 responses is discussed.
J Exp Med 1989 Dec 01
PMID:Two types of mouse T helper cell. IV. Th2 clones secrete a factor that inhibits cytokine production by Th1 clones. 253 Nov 94

The employment of a set of truncated dnaK peptides produced by deletion and insertion mutations in the Escherichia coli dnaK gene allowed us to define regions of the dnaK protein which are involved in particular enzymatic functions. The results obtained suggest that the dnaK polypeptide is organized into at least two distinct functional domains. The highly conserved amino-terminal portion is required for the ATPase activity. The carboxyl-terminal portion, characterized by relatively low similarity among species, is responsible for the autophosphorylating activity. The mutant dnaK protein C[74], which lacks amino acid sequences at the extreme carboxyl-terminal portion of the protein, retains both the ATPase and the autophosphorylating activities. The results obtained with the full-length (70-kDa) dnaK756 protein suggest that the thermolabile defect of the dnaK756 mutation affects directly or indirectly the ATPase active site of the enzyme. The autophosphorylating activity of the dnaK+, dnaK756, and C[74] polypeptides was activated at least 10-fold by the addition of CaCl2.
J Biol Chem 1989 Dec 15
PMID:Functional domains of the Escherichia coli dnaK heat shock protein as revealed by mutational analysis. 253 44

Serial determinations of beta-thromboglobulin (BTG), platelet factor 4 (PF4), fibrinopeptide A (FPA), antithrombin III (ATIII), protein C (PC), fibrin (ogen) degradation product (FDP), FDP D-dimer, activated partial thromboplastin time (APTT), prothrombin time (PT), and euglobulin lysis time (ELT) were performed in 18 patients with non-progressing stroke and 14 patients with progressing stroke in order to predict the development of progressing stroke. Increasing levels of BTG, PF4 and FDP with frequent fluctuation were noted in both kinds of stroke. Fluctuation of FPA levels was also noted but was less pronounced. PC levels were found to be slightly decreased with fluctuation but the mean was still in the lower normal limit. BTG, PF4 and PC all elevated at the time of deterioration of physical condition in patients with progressing stroke, whereas FPA had no definite change at that time. From our study, we conclude that both platelet activation and coagulation process do occur in both kinds of stroke. But the latter plays a minor role in the formation of thrombosis. The hemostasis change, especially concerning the thrombosis formation, probably plays a role in the development of progressing stroke, but we cannot predict their development even by the detections of the newly known molecular substances appearing in various steps of the hemostatic mechanism. Development of new tests for understanding the whole dynamic change of the thrombosis process is necessary for accurate prediction of the progressing stroke in the future.
Thromb Res 1989 Dec 01
PMID:The serial hemostasis-related changes in patients with cerebral infarction: comparison between progressing and non-progressing stroke. 253 1

This paper describes an adjuvant-free immunization regimen that results in the priming of T cells but not B cells. B10.A mice were primed s.c. with syngeneic spleen cells that had been pulsed with the peptide 81-104 derived from pigeon cytochrome c. The T cell response was measured by using a sensitive limiting dilution assay that measures lymphokine production. The precursor frequency of Ag-specific cells found in these mice was indistinguishable from the frequency found in mice primed in the footpads with 81-104 in CFA. A striking difference in antibody induction was found, however, when these two immunization regimens were compared. Mice primed with 81-104 in CFA developed significant serum antibody responses against the peptide, whereas mice primed with Ag-pulsed spleen cells produced no detectable anti-peptide antibodies. This lack of antibody did not result from detectable differences in the T cells that were primed: no differences were seen in IL-2 and IL-4 production or in the ability to provide help to B cells in vitro. In vitro stimulation with LPS suggested that the B cells were not primed by the Ag-pulsed spleen cells. The B cells were not tolerized, however, because boosting the mice with Ag in CFA resulted in the induction of an antibody response. The failure to induce an antibody response by priming with Ag-pulsed spleen cells was not caused by the site of immunization or the total amount of Ag used for priming. The critical variable may be the introduction of the Ag on the surface of an APC; in this form, B cell Ag recognition was apparently inefficient, whereas T cell Ag recognition was optimal.
J Immunol 1989 Dec 15
PMID:In vivo priming of helper T cells in the absence of B cell activation. 255 72

The explosive nature of the coagulation cascade led many scientists to investigate how it is regulated. Proteinase inhibitors such as antithrombin III inhibit active proteases of the coagulation cascade. Cofactors such as factor Va and factor VIIIa are proteolytically inactivated by activated protein C. Protein C is activated by the thrombin-thrombomodulin complex on the endothelial cell surface. Thus, the independent actions of the proteinase inhibitor system and the thrombomodulin-protein C system complement each other to maintain regulation of blood coagulation. The thrombin binding site of thrombomodulin was identified to be the fifth and sixth repeats of the epidermal growth factor-like domain. The same binding template contains sufficient information to block the functions of thrombin as a procoagulant. However, additional repeats are required for the activation of protein C. Thrombomodulin is the first example which illustrates that the epidermal growth factor-like domain functions as a binding template for thrombin and as a switch to turn off the procoagulant activity of thrombin as well as to trigger the protein C anticoagulant pathway. Epidermal growth factor-like structures are found in many of the coagulation factors. Complex formation is a repeated theme not only in the blood coagulation cascade but also in the thrombomodulin-protein C anticoagulant pathway.
Nihon Ketsueki Gakkai Zasshi 1989 Dec
PMID:The role of complex formation and epidermal growth factor-like domains in the regulation of blood coagulation by the thrombomodulin-protein C system. 256 Aug 86

A group of 23 children with cerebrovascular occlusion of unknown etiology were re-evaluated 6 months-2 years later. Plasma protein C levels were determined with the coagulation method and were low in 10 cases. The role of this deficiency and the necessity of this test in cerebrovascular occlusion is discussed.
Eur J Pediatr 1989 Dec
PMID:Role of protein C in childhood cerebrovascular occlusive accidents. 261 12

A girl with multiple congenital anomalies and a tendency to severe pyogenic infections was found to have an interstitial deletion of chromosome band 2q14----q21. Unusual facial manifestations included enophthalmos, long philtrum, micrognathia, narrow forehead, prominent glabella, and depressed nasal bridge. Unilateral corneal clouding, with Peters-like anomaly; agenesis of the corpus callosum; brain atrophy; and heart, kidney, hand, and dermatoglyphic anomalies were additional findings. Eye anomalies were observed in five of 22 patients with deletions of chromosome 2q. In comparing these cases, it seems that deletions of bands 2q21 and 2q31 are variably associated with microphthalmia, corneal clouding, cataracts, and Peters anomaly. Measurement of protein C and interleukin-1 (IL-1) did not show a gene dose effect, but the pyogenic infections and low IgA found in this patient may reflect an abnormality of IL-1 not detectable by our methods.
Am J Med Genet 1989 Dec
PMID:Interstitial deletion 2q14q21. 262 55

Current models suggest that Ag undergoes proteolytic cleavage in APC and that resultant peptide fragments associate with class II histocompatibility glycoproteins before recognition by helper T cells. Little direct information is available concerning the physical structure and membrane association of Ag processed under physiologic conditions. A model system, employing a series of biotinylated insulin derivatives, was used to examine the domains of Ag that are presented by APC. We reasoned that avidin should block the response of T cells to a given derivative only if biotin is retained on the functionally relevant form of Ag after processing. By utilizing derivatives modified at selected sites one should be able to determine whether specific sites remain after processing. By using F1 APC pulsed with biotinyl-insulin derivatives modified through the free amino groups of the A1, B1, or B29 amino acids, and T cell hybridomas restricted to I-Ad or I-Ab, we found that avidin inhibited the I-Ad-restricted response to A1, but not B1 or B29 derivatives. By contrast, specific inhibition of the I-Ab-restricted response was observed by using all three derivatives. These results suggest that the processed form of insulin recognized in association with I-Ab is largely intact and includes residues from both chains (A1, B1, and B29). The differential inhibition observed by using T cells restricted to different class II alleles demonstrates that processed Ag associated with I-Ab differs in conformation or structure from that associated with I-Ad. This experimental approach should prove valuable in characterizing the actual structure of processed Ag recognized by T cells.
J Immunol 1989 Dec 01
PMID:Probing the structure of processed antigen by using biotin and avidin. MHC-dependent inhibition of responses to selected biotinyl-insulin derivatives. 268 18


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