Tuesday, January 18, 2011

AMI and CMI in RA

So I was thinking that AMI and CMI are separate, discrete processes. Nope. You can have both!

I'm talking about the human immune response. AMI is antibody-mediated immunity and CMI is cell-mediated immunity. The chemical messengers are cytokines, histamines, prostaglandins, and leukotriennes. (Spell check doesn't like prostaglandins and thinks perhaps I mean prostitution. And for leukotriennes perhaps I really meant to say crestfallenness.) Anyway. I thought AMI led to certain conditions and CMI to others.

Today I was reading about RA (rheumatoid arthritis) and trying to figure it all out. See, RA starts out as an AMI process, then CMI jumps in.

RA starts with some unknown, unidentified, and probably variable antigen. The body makes an antibody for that mysterious antigen, and this antibody is called RF, rheumatoid factor. They can do a lab test to check for RF in your blood; that helps the physician diagnose the condition. So far this is AMI.

Then the RF antibody gloms onto the antigen, they get into a wrestling match and fall down into the synovial tissue of your joint. Now this isn't just one antigen-antibody wrestling match, oh no, it's happening in joints all over your body.

When the antigen and antibody hook up, this is called an immune complex. The immune complex, like I just said, falls into the synovial tissue. Let's say it jabs into the tissue. This causes inflammation. Now the cells of the CMI system run over and start multiplying. T cells and cytokines jump in and try to quell the inflammation, but they actually just make things worse.

When the T cells attack the immune complexes, it just causes more inflammation and more damage. Tissue erodes. Fluids, connective tissue, and even bone are eaten away by these inflammatory processes. You can see the damage in the fingers, you know, when someone has RA.... their fingers splay out crookedly and their knuckles are all swollen. That's the inflammatory process gone postal.

So. RA. AMI and CMI. Too many firefighters at the fire. They get too excited and chop down the house.