Monday, September 30, 2013

Little green men


Here they come, a fleet of space ships, landing on a tiny asteroid, sinking their test probes through the crust into the body of the orb (click to enlarge).

Well, no. We are looking at viruses attacking a bacterium, a provocative image from the 23 August issue of Science. They have attached themselves to the cell wall and are injecting their genome, syringe-like, into the body of the cell, where it will hijack the bacterium's reproductive machinery. I can't tell you how the image was made, because no info was given, but I can't stop looking at it. A little skirmish in the never ending cell wars, on a scale too small to be visible with the best optical microscope.

Viruses are the most numerous biological entities on Earth. We live and breathe in a sea of viruses. No one is quite sure of their origin. Are they alive? They can't reproduce on their own. They need living cells. My cells sometimes.

Achoo!

We have defenses, of course. A vast security system evolved to recognize and crush alien invaders, pathogens of every sort. The body's first line of defense is the outer walls: the skin, with its impregnable barrier of keratin, and the mucus membranes. Other exterior membranes are flushed with fluids: saliva, tears, and nasal secretions. The skin and the lower intestinal tract harbor populations of benign bacteria that do battle for the body the way pacified tribes on the marches fought for the Roman Empire.

Most effective of all the body's defenses are the lymphocytes, the agents of the immune response. Lymphocytes are small, round, non-dividing cells that are always on the alert. At any time there are as many as 2 trillion lymphocytes patrolling the human body.

And we have something no other plant or animal can muster: brains smart enough to extend and supplement the defenses nature gave us. I got my flu shot last week. Gave my immune system a boost. My wife was one of the last Americans to get polio. This before I knew her, and just before Jonas Salk gave his vaccine to the world in 1955. One brilliant human brain against that fleet of little green men from outer space.