IL-4 and IL-13 activate the JAK2 tyrosine kinase and Stat6 in cultured human vascular endothelial cells through a common pathway that does not involve the gamma c chain.

IL-4 and IL-13 each act on human endothelial cells (ECs) to induce expression of vascular cell adhesion molecule-1. On hematopoietic cells. IL-4 responses may be mediated either through a pathway involving gc, the common signaling subunit of the IL-2, IL-4, IL-7, IL-9, and IL-15 receptors, or through a gc-independent pathway that may be alternatively activated by IL-13. We find that human ECs do not express gc, as detected by indirect immunofluorescence and FACS analysis or by a reverse transcription-PCR method. Like IL-4, IL-13 activates a protein tyrosine kinase that phosphorylates the IL-4R binding protein. In addition, we find that IL-4 and IL-13 each induce tyrosine phosphorylation of the JAK2 tyrosine kinase. Furthermore, both IL-4 and IL-13 induce binding of the Stat6 transcription factor to a consensus sequence oligonucleotide. We conclude that the IL-4 response of human ECs involves the IL-13 shared pathway that is independent of gc, and uses JAK2-Stat6 signaling.

IL-4 induction of VCAM-1 on endothelial cells involves activation of a protein tyrosine kinase.

IL-4 triggers tyrosine phosphorylation of a single major substrate (M(r) 145,000) in cultured human endothelial cells (EC) as detected by Western blot of whole cell lysates or of anti-phosphotyrosine immunoprecipitates. Phosphorylation of this substrate depends on IL-4 concentration (appearance at 10 U/ml, maximal at 300 to 1000 U/ml) and time of treatment (onset by 1 min, peak at 5 to30 min, duration of 60 to 120 min). Immunoprecipitation with specific mAb identified the phosphorylated substrate as the IL-4R. Treatment of EC with IL-4 alone causes only a small increase in the expression of vascular cell adhesion molecule-1 (VCAM-1), but IL-4 significantly augments the level of VCAM-1 expression induced by PMA. Pretreatment of EC with herbimycin A (0.5 to 1.0 microgram/ml) for 12 to 18 h abrogates both IL-4-induced tyrosine phosphorylation and IL-4-augmented VCAM-1 expression. This concentration of herbimycin A does not inhibit and may augment PMA-induced VCAM-1 expression in replicate wells. These observations suggest that IL-4 induction of VCAM-1 in EC involves the activation of an as yet unidentified protein tyrosine kinase that phosphorylates the IL-4R.

An ELISA sandwich capture assay for recombinant fusion proteins containing glutathione-S-transferase.

A sandwich capture ELISA technique is presented for detection of recombinant proteins sharing a common affinity domain or reagents such as antibodies that bind to these proteins. An activated carrier protein (BSA) is modified with reduced glutathione (GT), forming an affinity capture reagent for glutathione-S-transferase (GST) and recombinant fusion proteins bearing the GST moiety. GT-BSA is immobilized on microtiter plates, and a sandwich is formed consisting of the recombinant fusion protein, reactive antibodies, and detection antibodies. An example is given that demonstrates that this format yields equivalent results to a conventional ELISA test with a panel of newly diagnosed diabetic sera reacting with an islet cell autoantigen.

Cloning and expression of IDDM-specific human autoantigens.

A DNA cloning approach was taken to identify islet cell protein antigens that are recognized specifically by insulin-dependent diabetes mellitus (IDDM) sera. A human islet cDNA library was generated and screened with diabetic sera. In this article, identification of two clones is described. Proteins expressed by these lambda phages appeared to react specifically with newly diagnosed diabetic sera. Islet cell antibody 12 (ICA12) was tested by Western blotting. ICA512 was not reactive with sera in the Western format but was specifically immunoprecipitated by diabetic sera from an Escherichia coli extract.

The effect of recombinant erythropoietin on intracellular free calcium in erythropoietin-responsive cells.

We have investigated whether recombinant erythropoietin (r-Epo) elicits a change in intracellular free calcium (IFC) in purified Epo-responsive cells in spleens of mice treated with phenylhydrazine. Colony-forming units (CFU-E) were prepared by negative selection through immunologic panning. Anti-Forssman, Mac-1, Ia, and HSA antibodies were used to eliminate nonhematopoietic progenitors. After two pannings, 29 +/- 1.5% (mean +/- 1 SD) of the recovered cells were CFU-E. IFC was measured by labeling cells with the fluorescent dye Indo-1 and analyzing them on a flow cytometer from 15 seconds to 30 minutes after the addition of agonist. At each step of the panning procedure, there was no effect of r-Epo (0 to 10 U/mL) on IFC even in the larger cells that are predominantly CFU-E. As a positive control, calcium ionophore (A23187) significantly increased IFC in greater than 90% of the spleen cells enriched in CFU-E. During growth of CFU-E in methylcellulose, the calcium ionophore did not affect the r-Epo-dependent formation of erythroid colonies. EGTA inhibited the formation of erythroid colonies. This inhibition appeared to be the result of a toxic effect of the chelator because the colony growth could not be restored when Ca2+ was added to the cultures in the presence of the EGTA. We conclude that the biologic action of Epo on responsive erythroid cells does not depend on acute changes in IFC.