Systemic lupus erythematosus

Alright, “systemic lupus erythematosus,” k we totally got this. “Systemic” is easy, and refers to affecting multiple organs in the body.

“Erythematosus” means reddening of the skin, alright alright.

“Lupus” is latin for “wolf”. So affects multiple organs wolf...reddening of the skin?

Not exactly, the modern use of lupus usually refers to a variety of diseases that affect the skin...which was possibly originally used since these diseases resemble a wolf bite on the patients’ skin.

Is that true? Who knows. At any rate, systemic lupus erythematosus, or SLE, sometimes just lupus, is a disease that’s systemic, and affects a wide variety of organs, but notably often causes red lesions on the skin.

But how does lupus affect all these organs? Well usually the immune system protects the body’s tissues from invaders, but lupus is an autoimmune disease, which means that immune cells start attacking the very tissues their supposed to protect.

With lupus, essentially any tissue or organ can be targeted.

And just like a ton of other autoimmune diseases though, it’s not completely clear why it develops, and like most diseases it’s the result of both genetics and the environment.

Alright so let’s go over a specific scenario to show how this plays out.

Let’s say this guy has susceptibility genes—genes that make him susceptible to getting lupus, and he’s exposed to UV radiation in sunlight, which we know is an environmental risk factor for lupus.

Well, given enough UV rays, think like sunburn, the cell’s DNA can become so badly damaged, that the cell undergoes programmed cell death, or apoptosis, and it dies.

This produces all these little apoptotic bodies, and exposes the insides of the cell, including parts of the nucleus, like DNA, histones, and other proteins, to the rest of the body.

Well those susceptibility genes specifically have an effect on this person’s immune system such that their immune cells are more likely to think that these are foreign, or antigens, and since they’re from the nucleus, we call them nuclear antigens, and immune cells try to attack them.

Not only that though, susceptibility genes also cause this person to have less effective clearance, essentially they aren’t as good at getting rid of the apoptotic bodies and so they end up having more nuclear antigens floating around.

This means that B cells might swing by, see them, and start the production of antibodies against these pieces of nucleus, which are called antinuclear antibodies, and these guys are present in almost all cases of lupus.