Thursday, February 19, 2009

Who the F@#k Are You?

The charge was as ridiculous as it was unexpected. Last summer, Heather opened up a letter from the Pittsburgh Traffic Court that said I needed to come pick up my car from the impound lot, said vehicle having been towed for illegal parking.

If I remember correctly, she stuck her head out the front door to confirm that my blue 2001 Subaru Impreza hatchback was still parked in front of the house. Then she noticed that the impounded vehicle was a red Ford pickup truck. Also, on the date of the ticket we were both in West Virginia on an extended search-and-rescue training exercise.

Apparently, the ticketing officer had made a slight error in entering the license plate number — the tag number on the ticket was mine, which was why the letter had come to our house. But state records clearly show that that number doesn’t belong to a red pickup, so we were puzzled as to how the mistake had gotten so far without anybody catching it.

After talking with the traffic court folks on the phone, Heather sent a letter to the court explaining everything, and we forgot all about it.

Well, early this year the calls started coming from the collection agency. Not only had justice been blind enough to miss the more-than-reasonable doubt of the case, not only had she ignored Heather’s letter, but she had, Star-Chamber-like, carried out a legal proceeding without notifying the accused — remember, the summons for a traffic violation is the ticket, their letter was just an extra notification — found me guilty, waited until I was in default of the ruling I never heard about, and then passed me onto the collection folks.

The latter were hilarious; when I called with the evidence that it couldn’t have been my car, they not only said they couldn’t take it into consideration, but that I might wind up having to pay the ticket because it had gone into collection and so couldn’t be re-adjudicated by the court.

I’m normally a fairly placid guy (Heather tells stories of Sicilian fits of temper, but given her own short fuse, who really believes her?), but people who know me know I can be a stubborn son of a bitch when I think I’m right. I explained to the collection rep that I intended to call my attorney and make sure that they spent more getting the fine out of me than the state would pay them for the collection.

Amazing how talk of lawyers brings out the reasonable side of some people. She told me that I could certainly send whatever documentation I had to prove the vehicle in question couldn’t have been mine (for all I know, it’s still sitting in a Pittsburgh impound lot).

Well, I called the traffic court for some details on the actual violation, and when the woman there heard my story she said she could make the issue go away. I’ve got all the documents saved in case I need them, but since then I haven’t heard from the collection folks. We’ll see, anyway.

All of which is to say, identification is important, and a change in context — say, the same license tag on a different vehicle — shouldn’t mess up an accurate ID if you’re careful. This week’s entry is a study showing how the individual smell that each of us possesses remains identifiably constant despite the fact that our environment clouds the issue. The report comes from Jae Kwak and a team from Gary Beauchamp’s crew at the very interesting Monell Chemical Senses Center in Philadelphia.

First, some background. Eighteen years ago, Kunio Yamazaki (also from Beauchamp’s lab) reported that mutations in a gene normally associated with identifying pathogens and rejecting transplanted organs somehow made one mouse smell different than another.

What emerged in the next decade of research was a picture in which a system that everybody thought was meant only to help the body tag dangerous invaders (and the body’s cells they had co-opted) for destruction may actually have another, even older function: Picking and choosing among the many bits of protein, fats, and other chemicals that we ingest to create a unique bouquet of smells that belongs to each individual.

The genes involved are called the major histocompatibility complex (MHC) in vertebrates, or the human leukocyte antigens (HLA) in humans specifically. The produce a family of proteins that are the body’s ID cards, which infection-fighting white blood cells examine, like bouncers, to determine who belongs and who does not.

The MHC proteins, in their originally understood role, pick up fragments of the normal components in a healthy cell and display them in a kind of one-two code. If the MHC protein and the fragments are normal, the white blood cell does nothing. If either is wrong, though — say, the right MHC protein, but displaying a fragment of a virus that has infected the cell — the bouncer calls in the cops: “killer” white blood cells that destroy the infected cell before the virus can spread. It works like this:

Well, it turned out that the MHC proteins also seemed to be able to pick up fragments of normal cellular products, ingested food, perfume, who knew what, and released them from the body as smells. Since each individual (except identical twins) has a unique spectrum of these proteins, he or she also has a unique spectrum of smells. That works this way:

You can read a more complete explanation of how the system works on AMRG’s website.

This discovery resonated strongly with what search-and-rescue dog handlers had known for years: both our genetics and the smells that normally surround us contribute to an individual scent that a trailing dog can follow, if given a scent article that individual has touched.

But the problem was, how can a dog recognize an individual human by smell — or any animal recognize another — when, potentially, you could give the smellee a substantially different bouquet just by changing environments? In other words, change utterly the palette of potential externally derived smells form which the MHC proteins select?

Well, Kwak and the Philadelphia gang showed that even when you change a mouse’s environment radically, the MHC proteins are able to scrape together enough familiar odor-carrying chemicals that another mouse trained to identify that individual could still tell that the smells were coming from the same mouse.

It’s a classic case of scientists confirming something dog handlers pretty much knew, but which is still vitally important in understanding the basics of how scent work happens. And, not inconsequentially, it establishes that, provided you do the training right [1], further demonstrates that there’s a healthy scientific basis for what dog handlers do to help find lost people.

Anyhow, Pittsburgh Traffic Court could take some lessons from tasks that dogs (and mice) carry out just about every day. We’ll see who turns out to be smarter.

[1] Do not, do not get me started.

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