Allergic reaction to an antibiotic (cephalosporins)

On meeting a fellow Doper this past weekend, it developed in conversation that we are both allergic to the class of antibiotics known as cephalosporins. She described her learning experience as an anaphylactic reaction whereas mine was described to me as a hemolytic drug reaction.

My layman’s grasp of medical vernacular interpreted hemolysis to mean a bursting of blood cells (that doesn’t sound too good). Neither one of us could explain how the allergic reaction (anaphylaxis v. hemolysis) could be as different (or possibly similar). Can one of y’all?

Your body made antibodies to the drug. The antibodies can initiate a reaction to burst blood cells (much like they can do for bacteria that you’ve been exposed to or vaccinated against) or they can initiate a Type I hypersensitivity reaction (allergy).

Only the anphylactic reaction is a true allergy, although both may be mediated by the immune system.

In the case of anaphylaxis or allergy, the person has an antibody of the IgE class directed against the “foreign” substance (in this case cephalosporins). This IgE, when released in response to and against cephalosporins, causes a fulminant destabilization of a class of cells called mast cells. Mast cells, when stimulated or destabilized, release all types of chemicals that cause things like swelling, low blood pressure, and constriction of the bronchi (breathing tunes), i.e. they cause anaphylaxis.

In the case of hemolysis, the body has produced an IgG type of antibody against the cephalosporin. This antibody either cross reacts with the person’s red cells or gets absorbed onto the surface of the red cells. In the former case, it leads to direct destruction (hemolysis) of the red cells, and in the latter case the presence of antibodies on the red cells leads to the cells being identified as “foreign” and that leads to them being cleared/destroyed by the immune system.

I seem to recall, as well, that cephalosporins may also directly alter RBC membranes and that too can lead to hemolysis. This is not an immunologic mechanism.

It is not uncommon for two people to have entirely different allergic reactions to the same substance.

Anaphylatic shock is a systemic response to the allergen; it involves multiple physiological systems. The allergen triggers an incomplete immune response, involving immunoprotiens and the release of large amounts of histamine. Much of the allergic reaction is caused by the excessive concentrations of histamine.

Hemolysis refers to the breakdown of red blood cells and the release of hemoglobin. This occurs normally at the end of the red blood cell’s life span but can also occur when there are metabolic abnormalities present; often as a result of allergic response.

Well, thanks for the input, although I’d have to admit most of it was over my head. So hemolysis does refer to a destruction of red blood cells. There are two classes of antibodies involved here, IgE and IgG, that trigger different reactions.

Antibodies, IIRC, work on the basis of molecular recognition (fitting) of surface proteins.

I remain unclear on the distinction between an anaphylactic “allergenic” response by antibodies produced in response to a prior exposure to cephalosporins and the “non-allergenic” hemolytic response by antibodies produced (presumably) by prior exposure to cephalosporins.

Sorry folks, I do appreciate your input, but sometimes it takes me a few rounds to get the idea.

An additional bit of input provided by the aforementioned fellow doper, that I cannot verify, was that most people who are allergic to penicillin are also allergic to cephalosporins, and she is not allergic to penicillin, while I am.

Me too!

In both cases, the body makes antibodies against the “foreign” substance. When the antibodies so produced are of the IgE class, the result can be allergy and/or anaphylaxis upon (re)exposure to that substance. When the antibodies produced are of the IgG class, the result is more benign and in fact usually quite beneficial, i.e. IgG antibodies are the ones that confer lifelong immunity against various viruses and the like.

I do not know why some people make (large quantities) of the IgE type of antibodies against certain substances (while others make IgG and still others make nothing). There is a genetic component presumably (allergy runs in families) and there may also be a role for premature and/or unusual exposures in early infancy. For example, in infancy, the stomach and intestines are immature and may allow certain substances to enter directly from the diet into the blood stream. This may lead to allergy to those substances later in life (it may also lead to so-called autoimmune diseases as well).

Of course, none of this addresses the issue of why only some people make antibodies to cephalosporins.

With respect to penicillin allergy, about 95% of people who are allergic to penicillin are NOT allergic to cephalosporins. I would estimate the converse is true also (that 95% of people with cephalosporin allergy ARE allergic to penicillin.

What we need here is a good immunologist! I am at my limit.

BTW, I was motivated to read a bit about the mechanism of cephalosporin-associated hemolysis and it seems there is yet another mechanism that I omitted. This mechanism is a combination of the ones I mentioned above. First, the cephalosporin gets adsorbed onto the red blood cell surface. It then gets attached to the surface. Then, if the person has already formed an antibody against freely circulating cephalosporin, that same antibody will damage the cephalosporin-red cell complex. This leads to hemolysis.

KarlGauss, I don’t know where we’re going with this, but I certainly do appreciate your input. Thanks.