Researchers have found that treating the transplant ratherthan the patient may help avoid potentially toxicimmunosuppressants required by transplant recipients.
Mice that received cell transplants that had been coated withfragments of antibodies were able to accept transplants ofhuman liver or pancreatic islet cells without any further drugtherapy, Boston scientists reported Friday in thejournalScience.
The researchers at Massachusetts General Hospital usedfragments of F(ab')2 antibody that recognize and latch onto theHLA class I antigens, which are immune-signaling moleculeson cell surfaces. Masking the HLA antigens apparently preventsthe triggering of rejection by T cells.
The islets survived more than 200 days; liver cells lived atleast 30 days. The transplanted islets also appeared tofunction. The researchers reported finding human C peptide, abyproduct of insulin secretion, circulating in the mice's blood.
This cellular masking strategy holds the most promise fortreating diabetics with implants of pancreatic islet cells.These cells, which produce insulin, trigger immune rejectionprimarily through the HLA class I antigens that stud theirsurface. Islet cells have few other immune triggers, thescientists reported, which makes HLA masking especiallyeffective in islet grafting.
The strategy will not eliminate the need for conventionalimmunosuppression in most transplant cases, in which wholeorgans are grafted. -- Roberta Friedman, Ph.D.
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