Blood pressure enzyme can have tumor-se...(ds the building blocks of proteins from ...),Health

But angiotensin is not ACE's only target. In previous studies, Bernstein and his co-workers found that manipulating its activity also affects processes such as fertility and the generation of red blood cells in the bone marrow.

To dissect out ACE's role in the immune system, they created mice with a genetic alteration in the ACE gene, forcing the gene to be turned on only in macrophages.

Macrophages are especially good at displaying peptides on their surfaces to other white blood cells called T cells so that the T cells are stimulated to grow. The T cells in turn kill virally infected cells. Depending on the situation, they can sometimes kill tumor cells as well.

When injected with several types of melanoma or lymphoma, the altered mice developed smaller tumors than normal mice. The tumors they did have contained more white blood cells attacking the cancerous cells.

In the JBC paper, the researchers show that ACE boosts cells' ability to display some foreign peptides, increasing their ability to stimulate T cells by several-fold.

Bernstein cautions that normally, macrophages make little ACE, so its effects must be seen as artificial. He notes that ACE inhibitors such as enalapril and lisinopril are taken by millions of people with high blood pressure and have not been reported to weaken the immune system.

However, cells similar to macrophages have been shown to produce ACE in response to pathogens such as sarcoid or leprosy, he says.

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