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 ca n develop urticaria or anaphylactic shock. Urticaria is mainly associated w ith positivity to the major determinant of benzylpenicillin (BPO), and anap hylactic shock with minor determinants (MDM). The presence of IgG antibodie s to BPO is thought to be mainly associated with urticaria, possibly protec ting from anaphylactic shock. We aimed to study the skin test response to B PO and MDM, amoxicillin (AX), and ampicillin (AMP) in a group of subjects a llergic to penicillins, and to evaluate the role of specific IgG. Methods: We studied a group of patients with immediate allergic reactions t o penicillins, comparing urticaria and anaphylactic shock. Skin tests were done with BPO, MDM, AX, and AMP. Specific IgE and IgG antibodies to benzylp enicilloyl-poly-L-lysine (BPO-PLL) and amoxicilloyl-poly-L-lysine (AXO-PLL) were determined by PAST and ELISA, respectively. Results: Fifty-nine patients were studied (30 with anaphylactic shock and 2 9 with urticaria). Skin test positivity to BPO was associated with urticari a (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-P LL IgG values were higher in patients than controls (P<0.001), but no diffe rences 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 c onfirmed. Abbreviations: BPO: benzylpenicilloyl; MDM: minor determinant mix ture; AX: amoxicillin; AMP: ampicillin; AXO-PLL: amoxicilloyl-poly-L-lysine ; BPO-PLL: benzylpenicilloyl-poly-L-lysine.