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I'm going to post this only to sci.med. The people on sci.med.diseases.cancer have more important things to worry about. In article <Pine.OSF.3.91.960623004400.12637A-100000@alcor.concordia.ca> you write: >> As I recall, lymph does a lot of garbage collection, and the lymph >> nodes look at the garbage to see if they should develop antibodies to >> it. It also drains fluid that has leaked from the blood system back >> to the heart. Does it have any other functions? >> >It's a reservoir for fluid leaking out of capillaries. It also transports >white cells too big to fit in capillaries. I thought lymph only flows in one direction, from the tissues to the lymph nodes. How do the white cells get into the lymph system in the first place? And where are the white cells used? >Sounds like a start Trek episode where Wesley's experiment went haywire. The Star Trek episode was very loosely based on nanotechnology. I've heard that originally it was supposed to be, not nanites, but *dust mites* that evolved very quickly. Mercifully, they realized that this was simply too stupid, reshot the opening sequence, and dubbed in "nanites" everywhere else. >If you wish to use nanotech robots, I would suggest that they play a role >similar to the immune system. Get them to locate and recognize tumoral >cells,and deliver a drug or other toxic agent directly to the abnormal cell. Adding nanotech robots to the blood stream has its own set of problems. You have to keep the immune system from attacking them; you have to cram a lot of smarts, a power source, a lot of sensing, and so on into something the size of a cell; you have to put enough of them in the blood that they are likely to bump into problem areas, but not so many that they interfere with the body's functioning; and it's hard for them to communicate with each other, so you may have problems doing something that you can't do with one cell-sized robot (microsurgery, for example). On the positive side, a cell-sized robot could easily destroy a cell mechanically--it wouldn't have to carry around drugs. I suspect that in the long run, a microsurgical approach to cancer will be better than a drug-based approach. When the cancer is found, a robot (either cell-sized or a RoboBlood extension) mechanically destroys every malignant cell that's connected to it. This is cleaner than waiting for a floating robot to bump into a cancer cell. >A big problem in cancer therapy is being ablr to target specific tunmoral >cells without destroying healthy cells. The best way of detecting cancers or cancerous cells remains to be seen, and will surely change as the technology changes. With RoboBlood you could just wait for it to grow into a blood vessel, then destroy it wholesale. There may be chemical markers that a smart catheter could follow to the source, then inject drugs into the area. (This could probably be done just with microtechnology.) Perhaps advances in MRI will be able to scan for very small cancers. But nanotechnology isn't a cure-all: the ability to build exquisitely small robots does not mean that we can design them easily. Suppose you were blindfolded and put in a room filled with bean bags, and told to pick out the one that was filled with a different kind of bean. You might be able to do it by weight, or smell, or the sound it made when you poked it; but it wouldn't be easy. Now design a robot to do this. Currently, this might well be impossible. >The role of the immune system is not limited to fighting of external >infections. It also does other things like clean up dead cells, protect >the body from its own resident bacteria. Can you (or anyone else) tell me more about this? How do the resident bacteria make trouble? What's involved in cleaning up a dead cell? Wait for it to decompose,