The active component of marijuana may enhance the virus that causes a rare type of skin cancer, according to researchers at Harvard Medical School.

Researchers said low-doses of tetrahydrocannabinol (THC), the component in marijuana that produces the “high” users experience, enhances the ability of the skin cancer, Kaposi’s sarcoma, to infect cells and multiply.

While most people are not at risk of developing the Kaposi’s sarcoma herpes virus, AIDS patients and transplant recipients are at an increased risk of developing the disease.

The findings, reported in the August 1 issue of Cancer Research, a journal of the American Association for Cancer Research, offer cautionary evidence that those with weakened immune systems should speak with their doctors before using marijuana medicinally or recreationally.

For the study, researchers examined a culture of human skin cells, which are susceptible to infection and could provide a model of Kaposi’s sarcoma.

While previous studies indicated that marijuana smoking was associated with Kaposi’s sarcoma, this study demonstrate that THC itself can assist the virus in entering endothelial cells, which comprise skin and related tissue, the researchers said.

“These findings raise some serious questions about using marijuana, in any form, if you have a weakened immune system,” said lead study author Jerome E. Groopman, M.D., professor of medicine at Harvard Medical School, in a news release.