the immune system is CRAZY

I am ahead of my game right now, I am psyched and don't want to fall behind...so a short post.

I have been geeking out on HLA lately. HLA stands for human leukocyte antigen. This is a set of genes that encode something called the Major Histiocompatibility Complex, which is on cells that present antigens (read - bad stuff) to T cells, so they can trigger mechanisms to destroy said bad things.

There are many different HLA permutations, depending on which types of T cells they want to send messages to (CD4 or CD8). So what is the relevance to me, asks the reader? AUTOIMMUNE diseases. Here, the body turns on itself, in that it recognizes certain cells in the body as foreign and wants to destroy them. Obviously not good, since the body actually needs those cells. A classic exam is type 1 diabetes, where the islet cells on the pancreas that make insulin are destroyed, so uptake of glucose into cells that need it in the body is impaired. These pancreatic cells are destroyed by the body itself! Not some outside interloper. Cool stuff, unless they are your islet cells.

Even more interestingly, certain autoimmune diseases are linked to the same HLA type. Diabetes type 1 is linked to Rheumatoid Arthritis, via HLADR4. There's a whole slew of arthritis oriented disorders linked to HLAB27, including arthritis that you can get after having chlamydia. Even if you treat the chlamydia, you are still at risk for developing this arthritis (called reactive arthritis - used to be called Reiter's arthritis, but they are trying to get away from it because Dr. Reiter was a Nazi doctor, and you know what those dudes were up to).

And with that...back to the thymus.

A cancer you can treat with vitamin A

Quick post today -

Acute myelogenous leukemia. A leukemia is a cancer of the bone or bone marrow. Myelogenous means that the cancer itself produces a lot of myeloid cells, which are neutrophils, macrophages, platelets, eosinophils, basophils, red blood cells. However, because it is a cancer, these cells are not fully developed, and are still in their 'myeloblast' (precursor) stage which is undifferentiated. Acute means onset is quick/sudden.

There is a form of acute myelogenous leukemia (AML for short), that is responsive to VITAMIN A. This very specific cancer (M3 type) has a translocation between chromosomes 15 and 17. You give these patients vitamin A and it forces these myeloblast cells to go from just hanging out in this amorphous undifferentiated state, to develop into regular cells. This way these weird precursor cells develop and stop crowding out all the other cells, like red blood cells. So cool.

However, I just learned that this cancer has something called Auer rods in the myeloblasts (which I knew already) that have peroxidase in them (which I didn't know - think hydrogen peroxide and what it does - that is what peroxidase does). If you treat the cancer, you release this peroxidase into the blood stream and you get something called DIC. Have we made up a plethora of dirty mnemonics around DIC? Clearly.

DIC stands for disseminated intravascular coagulopathy. Here, you clot like crazy. So crazy that you use up all your clotting factors, and start bleeding and not clotting anymore. Good times.

Am homing in on the end of hematology, just have the drugs to do.

the journey continues.