A variety of research studies are underway at area medical schools and hospitals, from figuring out why lung transplants arent as successful as other organ transplants to whether stem cell therapy can help avoid amputations.

Using drugs to broadly suppress the immune system helps the body accept organ transplants of hearts, livers and kidneys. But not so with lung transplants, new research at Washington University School of Medicine suggests.

In what researchers call a surprising discovery, newly transplanted lungs in mice were more likely to be rejected if key immune cells called memory T cells were missing. Typically, memory T cells are knocked down with immunosuppressive drugs.

Memory T cells patrol the lungs for invaders from the environment such as viruses and bacteria. When researchers infused memory T cells into mice with lung transplants, the cells released signals that encouraged the immune system to accept the lung.

The research may help partly explain why lung transplants are not as successful as other organ transplants. Five years after lung transplants, only half are still functioning, figures show.

Researchers want to discover how to target immunosuppression in lung transplants in a way that would help memory T cells thrive while eliminating other T cells that are harmful.

Also at Washington U., researchers have found that a follow-up surgery after a stroke to clear fatty deposits from the neck should be delayed if the patient was recently treated with the clot-busting drug tPA.

After a stroke, physicians scan two large blood vessels in the neck, which provide much of brains blood supply. If one is more than 50 percent blocked with plaque, doctors commonly recommend surgical removal of the plaque called carotid endarterectomy a few days after the stroke to help reduce the chance a fragment will break free and cause another stroke.

Analyzing outcomes of 142 patients, researchers found those who received the surgery a few days after being treated with tPA were at higher risk for bleeding complications in the brain.

It may be that tPA caused microhemorrhages in the brain that surgery could worsen without allowing time for the blood vessels to heal; or tPA could be activating a molecular chain reaction that temporarily increases the risk of bleeding in the brain.

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In the lab: Researchers uncovering clues to lung transplants and more