Quantitation of soluble HLA-DR antigens in human serum and other body fluids

The existence of soluble forms of MHC class II molecules is well established. To quantify soluble HLA-DR antigens (sHLA-DR) in human serum and other body fluids, we developed an enzyme immunoassay using two non-overlapping HLA-DR-specific monoclonal antibodies (RoDR, BL-la/5) and an immunoaffinity chromatography-purified sHLA-DR standard. In serum of healthy individuals, sHLA-DR levels were found in the range between 0.6 and 3 ng/ml (median 0.85 ng/ml) whereas EDTA plasma samples showed concentrations about 20 times higher (median 21 ng/ml). In tears, saliva, sweat, urine, amniotic fluid, cerebrospinal fluid, and bronchoalveolar lavage, sHLA-DR could also be detected. No association was found between sHLA-DR serum levels and distinct HLA specificities. In the sera of patients with autoimmune diseases, slightly enhanced sHLA-DR values were found (juvenile rheumatoid arthritis: median 2.0 ng/ml, lupus erythematosus: 1.5 ng/ml, diabetes mellitus: 2.1 ng/ml).

[Follow-up study of the development of autoantibodies in patients with chronic inflammatory bowel disease under anti-CD4 therapy]

7 of 22 patients with chronic inflammatory bowel diseases (Crohn's disease, ulcerative colitis) were treated with an anti-CD4-mAb. In the immunological monitoring the amounts of autoantibodies to pancreatic acini cells, to intestinal goblet cells, to granulocytes with perinuclear fluorescence pattern were examined and human anti-mouse-antibodies were measured. After anti-CD4 therapy the production of autoantibodies was widely unchanged. Therefore its use as parameter in the follow-up is restricted.

[The local specific immune response to Staphylococcus aureus protein A in human tonsillar lymphoid tissue]

Formation of antibodies and development of delayed hypersensitivity to protein A are usual components of the immune response of tonsillar lymphoid tissue to S. aureus infection in chronic tonsillitis in man. The preparations of transfer factor, produced from human tonsillar T-cells, show increased activity in the intraspecific transfer of delayed hypersensitivity to staphylococcal protein A from humans to mice.

Processing of insulin by bovine endothelial cells in culture. Internalization without degradation

Insulin binding and processing was studied in monolayer cultures of bovine aortic endothelial cells. Specific 125I-insulin binding was both time and temperature dependent. Maximum binding at 37 degrees C occurred at 90 min, and was 3.8%/mg protein and, at 15 degrees C, 7%/mg protein at 4 h. 125I-insulin was crosslinked to its receptor using disuccinimidyl suberate (DSS), and the structure of the receptor complex was identified by SDS-polyacrylamide gel electrophoresis and autoradiography; a major band with Mr = 145,000 was identified, which corresponds to the alpha-subunit of the insulin receptor reported in other tissues. Receptor-bound insulin was internalized, and both the rate and the amount of internalization were temperature dependent. The rate of internalization was slowest at 4 degrees C, and fastest at 37 degrees C, and the maximum amount of 125I-insulin internalized in 120 min was 16% at 4 degrees C, 45% at 15 degrees C, and 81% at 37 degrees C. Despite the high rate of internalization, endothelial cells do not appear to degrade insulin significantly, as determined by gel chromatography and TCA solubility (7% at 4 h) of media-associated radioactivity. In addition, the majority of internalized insulin (75%) was released by 60 min, largely as intact insulin. Chloroquine treatment at high concentration did not exert any major effect on insulin binding or degradation within the first 60 min, but thereafter produced a marked increase in cell-associated radioactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization and partial purification of an endothelial cell growth factor from human platelets

Platelets have been shown to affect the growth of vascular endothelial cells. This report describes the characterization and partial purification from human platelets of a novel growth factor which can stimulate human endothelial cells to synthesize DNA and grow. Platelets were lysed by sonication and the particulate fraction removed by ultracentrifugation at 100,000 g. The supernatant of the platelet lysate stimulated the incorporation of [3H]thymidine into DNA of endothelial cells by 20-fold and caused a threefold increase of cell number in 2 d in culture. Gel filtration on Sephacryl S-200 and dialysis with exclusion membranes resulted in a 50-fold purification of this growth-promoting substance. Two peaks of endothelial-growth factor (ENDO-GF) were observed with apparent molecular weights of 65,000 and 135,000. Further characterization showed that ENDO-GF differed from platelet-derived growth factor since it was very heat labile and more potent in stimulating growth in endothelial cells than in fibroblasts. The isolation of an ENDO-GF from platelets suggests that platelets may have a role in the growth and healing processes of human endothelium.

Differential responsiveness to insulin of endothelial and support cells from micro- and macrovessels

The pathologies of diabetic micro- and macroangiopathy are different, suggesting that diabetes affects these two types of vascular tissue in a dissimilar manner. We have compared insulin receptors and the effects of insulin on cultured endothelium from calf retinal capillaries and aorta, and the vascular supporting cells, retinal pericytes, and aortic smooth muscle cells. 125I-insulin binds to high affinity insulin receptors on all four cell types. Receptor concentrations were similar except for aortic smooth muscle cells, which have 10-fold fewer receptors than the other cell types. Insulin at a concentration of 10 ng/ml stimulated [14C]glucose incorporation into glycogen in retinal endothelial cells and pericytes and aortic smooth muscle cells, but had no effect on aortic endothelium. Insulin over a concentration range of 10 ng/ml-10 microgram/ml, stimulated [3H]thymidine incorporation into the DNA of retinal pericytes, and endothelial cells and aortic smooth muscle cells but had no effect on aortic endothelial cells. These data suggested that a differential response to insulin may exist between endothelium of micro- and macrovasculature, and suggest that retinal capillary endothelium and retinal pericytes are both very insulin-sensitive tissues.