A comparison of allergen and polycation induced cutaneous responses in the rabbit

Allergic inflammatory responses contribute to the symptoms of a number of diseases including atopic dermatitis, asthma and rhinitis. Cationic proteins are released from inflammatory cells and levels are known to be raised in disease states. Using an in vivo model of acute inflammation, we investigated the characteristics of cutaneous responses to antigen (Alternaria tenuis, AT) and poly-L-lysine (PLL, used as a paradigm for cationic proteins). We aimed to compare the inflammatory profile of cationic polypeptides and the allergic response and to identify similarities and differences between these responses. Responses to intradermal injection of the polycation, PLL and antigen were compared using radiolabelled protein ((125)I-bovine serum albumin, BSA) and cells ((111)In-neutrophils, PMN) to study plasma exudation (PE) and PMN accumulation (PMNA) in the skin of AT sensitized rabbits. Both PLL and antigen caused dose-related increases in PE and PMNA. PE (and PMNA) responses to PLL were prolonged (up to 3 h), as were those to antigen. This is in contrast to PE responses to fMLP which were maximal at 45 min. In immunized animals, treated with colchicine (1 mg kg(-1) i.v.), PE responses to the directly acting mediator, bradykinin (BK), were not affected, whereas PE responses to the neutrophil dependent mediator, f-met-leu-phe (fMLP), were significantly (P<0.01) reduced. Antigen-induced PE responses were significantly (50, 500 (P<0.05); 200 (P<0.01) p.n.u. site(-1)) inhibited by colchicine, but PLL-induced responses were not significantly affected. We conclude that although PLL-induced responses had a similar time course to those of antigen, some differences were observed between responses, which indicate that although polycations may contribute to allergic responses, these two responses are produced by distinct mechanisms.