So that rash isn’t anything horrid apparently. My dermatologist, who is wonderful, described it as a mixture of eczema and very dry skin (sort of a mix of eczema craquelé, atopic dermatitis, and xerosis). She advised less frequent lukewarm showers, good moisturizer, and a high-potency steroid cream. Hopefully, the change in weather will allow us to get some humidity into the house, but the shower thing is a problem. I work in small rooms with sick people, so I shower once in the morning to avoid offense in the exam room, and once in the evening to avoid contagion at home. The doctor recommended a week in Florida, but that’s not on the agenda. The steroids should do it though, eczema being one of those diseases where the immune system is a bit irrationally exuberant.
Speaking of immunologic illnesses, I was confronted last weekend by an annoying case of common variable immune deficiency (CVID). The primary problem in CVID is a failure to make sufficient quantities of antibodies, the chemicals that mark biologic invaders for destruction. Antibodies are part of the adaptive arm of the immune system that recognizes specific invaders. The immune system also has a passive arm that can respond to molecules that look generally like invaders. Antibodies though are very specific. One may recognize a particular surface molecule on a staph bacterium, another an influenza virus.
The arms of the “Y” on the immunoglobulin molecule are the end that bind to antigens (molecules that form parts of various bacteria, viruses, and other invaders) and can bind very specifically, like a lock and key. Given the millions of foreign molecules we are exposed to, many of which are harmless, how can we possibly maintain a library of antibodies against invaders?
The immune system, specifically a type of white blood cell called a “B-cell”, creates antibodies whose structures are random. Not every one of these will bind pathogens. During development of immune cells, this part of the immune system is very closely regulated, so that immune cells that recognize “self” molecules are turned off. This culls out cells that would attack us, and (normally) leaves the ones we need to patrol for invaders. If an antibody happens to find an antigen that fits, it will bind, setting off a cascade of changes which will ultimately lead to production of more of that antibody. This way, a large repertoire of potentially useful antibodies are created, but only the ones that are needed are produced.
As a wise physician once told me, “antibiotics never cured anyone,” meaning that antibiotics generally help our own immune system gain control of an infection. In CVID, antibody production is impaired, so when the patient becomes ill, antibiotics may not be sufficient to save them. While penicillin may inhibit bacterial cell wall synthesis, antibodies can not only mark bacteria for destruction, but send out a chemical signal to call in more immune cells, evening the odds.
Patients with CVID often become much more ill from common infections that patients with normal immune systems. Since these patients cannot make enough of their own antibodies, one possible treatment is to give them antibodies from someone else. Since the antibodies are floating around in the plasma, perhaps we could simply give the patient a plasma transfusion. The problem here is that any single donor may not happen to have the specific antibodies needed. If, for example, my CVID patient had an infection with Streptococcus pneumoniae serotype 7F, but the donor had never been exposed to that and therefore did not have antibodies, the plasma would not be helpful. The solution is to take plasma from thousands of donors, pool it, and divide it up so that each unit will have a wide variety of antibodies. This is remarkably effective.
So as I spend my precious minutes under the lukewarm shower, I’ll contemplate the wonder that is the immune system, and the hard work that has gone into giving us the ability to manipulate it, allowing me to scratch less, and preventing another patient from dying of a normally curable disease.