Answer to the Friday Whatsit for December 31, 2010
No guesses for the last Whatsit of 2010. It was a challenging one, trying to guess the cell structure pictured here. The cells in this image have been stained with an antibody that picks up a protein found in tight junctions. So tight junctions was the answer we were going for.
A tight junction is a connection between two cells that completely seals the two plasma membranes together. It forms a solution and protein tight barrier where nothing can get through unless the cells on either side remove the junction. This type of junction is found in many places in the body where cells need to act as a single unit, often when those cells provide a barrier between ourselves and the outside world. Tight junctions between cells in the skin keep out bacteria, viruses and other things we don’t want entering our bodies. The cells that make up blood vessels have them to keep blood from leaking out until it gets to where it’s needed. White blood cells can signal to vessel wall cells that they need to get out and squeeze through these junctions to get to sites of infection. The cells of the intestine also have tight junctions to keep digesting food in the gut and to protect against food-bourne bacteria and toxins entering the rest of the body. When the food has been broken down into essential nutrients, these nutrients are carried through the intestinal cells themselves and released into the bloodstream.
Much of the current research into tight junctions is interested in how they are controlled by the cells. How are they assembled, when and why are they disassembled (during an infection or in the course of natural cell recycling), are these junctions compromised in diseases like inflammatory bowel disease, and are there ways that bacteria or other infectious agents can get through these junctions?