Healthy cells express a panel of microRNAs that help avoid unwanted recognition and attack from the immune system. A study online in Nature Immunology explains this process, and suggests the same mechanism may also help tumours to go undetected.
MICA and MICB proteins -- upregulated in times of stress such as a viral infection -- are recognized by the receptor NKG2D expressed on immune cells. Detection of these stress-induced proteins by these cells triggers an immune response that clears the source of stress. Viruses can evade this immune response using short stretches of RNA called microRNAs that suppress MICA and MICB expression.
Ofer Mandelboim and colleagues show that, like viruses, healthy non-stressed human cells also express microRNAs designed to dampen MICA and MICB expression. This allows healthy cells to escape detection by the immune system. Compared to healthy tissues, many human tumours express excessive amounts of these microRNAs. Importantly, this might also help tumours escape recognition by the immune system.
Ofer Mandelboim (The Hebrew University Hadassah Medical School, Jerusalem, Israel)
Abstract available online.
(C) Nature Immunology press release.
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