lmmunochemical mechanisms involved in tick rejection by a host are not well documented. The role of serum globulins, and that played by the amplification system's humoral products (thrombin from the coagulation, plasmin from the fibrinolytic, and kallikrein from the kinin systems) in tick-resistant animal hosts have not yet been demonstrated. It is known, however, that factors C1, C3 and C5 of the complement system play a role in tick rejection, and that factors C3a and C5a are anaphylatoxins capable of degranulating leukocytes, thereby releasing pharmacologically active vasoamines which are involved in tick rejection. In this study, levels of kininogen increased by 56% and those of fibrinogen by 19% in rabbits immunized with nymphal antigens. A highly significant (P <0,001) number of nymphs that fed on the immunized rabbits failed to moult into adult stages. It is reported for the first time, that increased levels of two glycoproteins, fibrinogen and kininogen occurred in rabbits immunized with homogenates of Amblyomma hebraeum ticks. The role played by the amplification system in tick rejection in resistant animals is clarified.
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