In a number of clinical circumstances it would be desirable to artificially conceal cellular antigenic determinants to permit survival of heterologous donor cells. A case in point is the problem encountered in transfusions of patients with rare blood types or chronically transfused patients who become allosensitized to minor blood group determinants. We have tested the possibility that chemical modification of the red blood cell (RBC) membrane might serve to occlude antigenic determinants, thereby minimizing transfusion reactions. To this end, we have covalently bound methoxy(polyethylene glycol) (mPEG) to the surface of mammalian RBC via cyanuric chloride coupling. Human RBC treated with this technique lose ABO blood group reactivity as assessed by solution-phase antisera agglutination. In accord with this, we also find a profound decrease in anti-blood group antibody binding. Furthermore, whereas human monocytes avidly phagocytose untreated sheep RBC, mPEG-derivatized sheep RBC are ineffectively phagocytosed. Surprisingly, human and mouse RBC appear unaffected by this covalent modification of the cell membrane. Thus, mPEG-treated RBC are morphologically normal, have normal osmotic fragility, and mPEG-derivatized murine RBC have normal in vivo survival, even following repeated infusions. Finally, in preliminary experiments, mPEG-modified sheep RBC intraperitoneally transfused into mice show significantly improved (up to 360-fold) survival when compared with untreated sheep RBC. We speculate that similar chemical camouf lage of intact cells may have significant clinical applications in both transfusion (e.g., allosensitization and autoimmune hemolytic disease) and transplantation (e.g., endothelial cells and pancreatic ␤ cells) medicine.The transfusion of red blood cells (RBC) is the most common, and best tolerated, form of tissue transplantation. Indeed, in 1993, over 14 million units of blood were donated for transfusion in the United States alone (1). In most transfusions, simple blood typing (ABO͞Rh-D) is sufficient to identify appropriate donors. Occasionally, however, appropriate donors for patients with rare blood types cannot quickly be found; a situation that may become life-threatening. More often, problems are encountered in individuals who receive chronic transfusions, such as patients with sickle cell anemia and thalassemia. In such patients, alloimmunization against minor RBC antigens can make it nearly impossible to identify appropriate blood donors (2-4). Previous studies in which purified proteins were covalently modified with poly(ethylene glycol) (PEG) provided a possible solution to this problem. PEG-modified proteins have been shown to have increased in vivo survival and to be nonimmunogenic, even with repeated infusions (5, 6). We therefore explored the hypothesis that the covalent binding of PEG to intact RBC might mask RBC surface antigens and thereby permit the survival of heterologous or even xenogeneic RBC.To experimentally test this hypothesis, human, mouse, and sheep RBC were...

Objective Vitamin D modulates the immune response and blocks induction of an interferon signature by SLE sera. We investigated the effects of vitamin D supplementation on the IFN signature in SLE patients. Methods 57 SLE patients with stable, inactive disease, a serum 25OH vitamin D (25OHD) ≤20ng/ml, elevated anti-DNA antibodies and an IFN signature (determined by measurement of 3 interferon responsive genes) were randomized into a 12 week double-blind placebo controlled trial of 0, 2000IU or 4000IU of vitamin D3. An IFN signature response required a 50% reduction in expression of 1 gene or a 25% decrease in 2 genes. Disease activity, adverse events and endocrine effects were assessed. Results Baseline characteristics of the 3 treatment groups were similar. No subjects receiving placebo repleted (achieved 25OHD levels ≥30ng/ml) compared to 16 of 33 subjects receiving vitamin D3. The percent of subjects achieving an IFN signature response did not differ between treatment groups. Moreover, there was no difference in the IFN signature response in vitamin D deficient versus repleted subjects. Modular microarray analysis of a subset (n=40) revealed no changes in any modules including the IFN-inducible module between any treatment group, nor when comparing expression data from vitamin D repleted to persistently deficient subjects. Vitamin D3 was well-tolerated with no safety concerns. Conclusions Vitamin D3 supplementation up to 4000IU daily was safe and well-tolerated but failed to diminish the IFN signature in vitamin D deficient SLE patients. Higher 25OHD levels sustained for longer duration may be required to affect immunological outcomes.

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Objective. To test the effects of a novel tylophorine analog, DCB 3503, on the prevention and treatment of collagen-induced arthritis (CIA) and to elucidate its underlying mechanisms.Methods. DBA/1J mice were immunized with type II collagen, and in some cases, lipopolysaccharide (LPS) was used to boost the development of arthritis.