THE NATURE OF THE CARRIER IN THE RAST ASSAY INFLUENCES THE CAPACITY FOR DETECTING IGE ANTIBODIES TO PENICILLINS

Radioallergosorbent test (RAST) systems using solid phase conjugates o f amoxicillin (AX) with three different spacers: poly-L-lysine (PLL), human serum albumin (HSA), and an amino spacer arm (S) were compared f or their ability to detect specific IgE antibodies to the amox-icilloy l side chain (AXO) in sera from allergic patients. Serum pools and ind ividual sera containing IgE antibodies specific for the 6-aminopenicil lanic (6-APA, the common structure of penicillins) or the side chain o f amox-icillin (characterized by RAST inhibition with monovalent hapte ns) were employed for validating the assays. Ah assay systems were abl e to detect IgE specific for the 6-APA portion of penicillins. However , when sera containing antibodies specific for the side chain of AX we re investigated, different results were found. RAST reagents prepared using an AXO-HSA conjugate detected only 12/24 (50%) of sera that had been positive with AXO-PLL system while AXO-S conjugate detected 22/24 (91.7%). A significant correlation was found between all three assays but the concordance was higher between the AXO-PLL and AXO-S assays t han between these and the AXO-HSA assays. These results show that the use of the carrier is relevant for the determination of IgE antibodies to penicillins.