「看」到免疫系統

Tagging cells makes immune system light up


以往我們只能抽抽血，跑跑flow cytometry，來看看這些免疫細胞的「血中」或是「體液中」分佈的濃度。有了這個東西，就可以真的「看到」白血球在人體中的分佈了～

WATCHING the immune system rev up in response to a tumour or attack the body's own tissue may one day give doctors an edge in monitoring and treating disease.

A surge in immune cells can be a first sign of cancer, while a reduction is a clue that a treatment for autoimmune diseases, such as rheumatoid arthritis or lupus, is working. However, these cells are difficult to detect as they are dispersed throughout the body and do not show up using conventional imaging techniques.

To make them more visible, Owen Witte and colleagues at the University of California, Los Angeles, developed a molecular "tag" called FAC that binds preferentially to immune cells over other types, and then lights up during a positron emission tomography (PET) scan.

When the researchers injected FAC into mice and took a PET scan, tissues rich in immune cells, such as spleen and lymph nodes, lit up, indicating that the FAC was working. In mice infected with a virus, and in mutant mice with autoimmune disorders, those tissues lit up more brightly than in uninfected mice or mice without autoimmune disease (Nature Medicine, DOI: 10.1038/nm1724). If the technique works in people, it should give doctors an easier way to monitor disease.

原文在：Nature Medicine, DOI: 10.1038/nm1724，FAC 是(1-(2'-deoxy-2'-[18F]fluoroarabinofuranosyl) cytosine)的縮寫。

but wait.......這個東西聽起來很神奇，但是在臨床上恐怕用處不大。因為白血球除了secondary lymphoid organ如淋巴結外，本來就會因chemotaxis聚到發炎的地方。也就是說，這個PET可以幫我們看「發炎的地方」。除了少數abscess在臨床上不好找，可以考慮這個方法(別忘了whole body CT可能更便宜)，要講到癌症的早期發現診斷恐怕還早。雖然部份癌症會有lymph infiltration，但更多的癌症是immune escape的...

可以考慮的方向是，找到個別淋巴球的marker如NK T(其他如Th, Treg, cytotoxic T, B)可能對癌症的早期診斷會更有幫助，而非找個所有淋巴球共同的marker....不過這樣大概很傷本吧！？