Immunologic Response to Different Determinants of Benzylpenicillin, Amoxicillin, and Ampicillin. Comparison Between Urticaria and Anaphylactic Shock

Background: Subjects with IgE-mediated allergic reactions to penicillins can develop urticaria or anaphylactic shock. Urticaria is mainly associated with positivity to the major determinant of benzylpenicillin (BPO), and anaphylactic shock with minor determinants (MDM). The presence of IgG antibodies to BPO is thought to be mainly associated with urticaria, possibly protecting from anaphylactic shock. We aimed to study the skin test response to BPO and MDM, amoxicillin (AX), and ampicillin (AMP) in a group of subjects allergic to penicillins, and to evaluate the role of specific IgG.

Methods: We studied a group of patients with immediate allergic reactions to penicillins, comparing urticaria and anaphylactic shock. Skin tests were done with BPO, MDM, AX, and AMP. Specific IgE and IgG antibodies to benzylpenicilloyl-poly-L-lysine (BPO-PLL) and amoxicilloyl-poly-L-lysine (AXO-PLL) were determined by RAST and ELISA, respectively.

Results: Fifty-nine patients were studied (30 with anaphylactic shock and 29 with urticaria). Skin test positivity to BPO was associated with urticaria (P<0.001), and positivity to MDM, AX, and AMP with anaphylactic shock (P=0.006, P<0.001, and P=0.002, respectively). Specific anti-BPO-PLL and AXO-PLL IgG values were higher in patients than controls (P<0.001), but no differences were observed between urticaria and anaphylactic shock.

Conclusions: Positivity to minor determinants of penicillins is associated more with anaphylactic shock than urticaria, but the role of IgG antibodies in helping to prevent the development of anaphylactic shock could not be confirmed.