The monster tumor

Q. What’s a dermoid cyst?

A. “Dermoid cyst” is a term that’s sometimes used to describe a benign form of a tumor called a teratoma (a pretty descriptive term, as we’ll see, as it comes from the Greek word for monster). (more…)

How to study for boards, part II

Today we’ll continue on in our little series of posts on how to study for boards. In part I, we talked about how to set up a study plan, and how to pick among all the resources available for students. (more…)

How to memorize the interleukins

I know a bunch of you are studying for boards, or are thinking about studying for boards. Any little memory aid that could help with a question or two is probably most welcome at this point.

Take, for example, all those cytokines with numbers (IL-1, IL-2…). How are you supposed to remember what all of those do?! Well, today’s post, written by a brilliant immunologist, gives you a great little method for remembering the interleukins associated with Th1 and Th2 cells.

You can keep the single digit interleukins straight because they come in sequence.

1. Macrophages can produce IL-1 which activates Th cells (CD4 T cells).

2. If the macrophages also produce IL-12, this will drive the Th cells to become Th1 cells (2 to Th1, or “to” Th1).

3. If Th1 cells are induced, they will produce IL-2 (second cytokine in order) and both IL-3 and IFN-gamma (gamma is the 3rd letter of Greek alphabet and represents the 3, too). The IFN-gamma will activate cytotoxic T cells (CD8 T cells).

4. If the macrophages produce only IL-1, this will drive the Th cells to become Th2 cells. If Th2 cells are induced, they will produce IL-4, IL-5, and IL-6 (note that they follow in order) that drive B cells to divide and differentiate into plasma cells that produce antibody.

5. Th2 cells also produce IL-10 (“zero Th1”) which blocks macrophage production of IL-12 and thus blocks activation of Th1 cells.

How do steroids inhibit the immune response?

Q. We heard in class today that steroids are used for autoimmune diseases, and I’ve heard this before but never understood why. What is it about steroids that make them effective as immunosuppressants?

A. There are lots of mechanisms by which steroids dampen the immune response. Here are a few of them:

1. Suppression of T cells. Steroids interfere with production of cytokines (like interleukins), which are critical in the proliferation and interaction of T cells.

2. Suppression of B cells. Steroids interfere with the binding of interleukins to B cells, which means that the B cells have a hard time proliferating and making antibodies.

3. Suppression of neutrophils. Steroids inhibit just about everything that neutrophils do: adhesion, chemotaxis, phagocytosis, and the release of toxic substances.

4. Suppression of macrophages. Steroids down-regulate the expression of Fc receptors on macrophages – so macrophages are less able to phagocytose opsonized things.

5. Diminished production of prostaglandins and leukotrienes. Steroids inhibit cyclooxygenase and phospholipase A2, which decreases the production of pro-inflammatory arachadonic acid metabolites.

Steroids are used in a ton of different immune and inflammatory disorders, like asthma, vasculitis, arthritis, gout, multiple sclerosis, sarcoidosis, alopecia areata…the list goes on and on.