penicllin structure and allergic reaction

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The reported history of penicillin allergy ranges from 0.7% to 10%

There are four classes of betalactam antibiotics: penicillins, cephalosporins, carbapenems, and monobactams.

The first three all have bicyclic nuclei in contrast to monobactams(aztreonam),

which lacks a second ring adjacent to the betalactam nucleus.

 

Major and minor determinants

The betalactam ring is unstable and readily acylates lysine residues in proteins.  

The penicilloyl epitope is produced, which is called the “major determinant” since over 75% of all IgE mediated reactions are directed against this epitope.

Beta lactams can also haptenize covalently through carboxyl and thiol groups, which results in a variety of less dominant or “minor” determinants. Minor determinant IgE responses have been associated with anaphylaxis, while penicilloyl IgE responses are usually associated with urticarial reactions