Answer to the Friday Whatsit for May 28th
Thanks to the quality educational experience of Not-So-Humble-Pie’s Blood Cell Bakery, this Whatsit was pretty easy to guess. Congratulations to Murph for guessing the identity of the cell in 47 minutes, which may be a new record!
The dyed-red cell is a CD8 T cell, picked out of whole mouse blood with antibodies to the TCR (T cell receptor, biologists come up with such clever names, don’t they?) and CD8 (a surface marker involved in the T cell’s normal function of killing compromised body cells). CD4, another surface marker on a slightly different kind of T cell, is also involved in a T cell’s normal function and also in the pathology of HIV/AIDS. The tube that the T cell is in is a blood vessel, of course.
T cells roll along blood vessel walls using surface proteins called integrins, which work sort of like cellular velcro. When they sense a cell in distress, T cells stop and latch on to that cell. CD4 “helper” T cells then help to get the word out to other cells of the immune system that there is a rouge cell in the body and everyone should come over and help get rid of it. T cells like this one, called CD8, cytotoxic or “killer” T cells, can kill the rogue cells directly. What causes a normal body cell to go rogue? Infection with bacteria or viruses, for one. In this case the green cells that the T cell has found have become cancerous and are part of a tumor. We know this because the tumor cells were marked with green fluorescent protein to make them easier to find and identify under the microscope.
So there you have it. Way Oversimplified Immunology 101 and the Answer to last week’s Friday Whatsit.