ACQUIRED-RESISTANCE TO TICKS .3. COBRA VENOM FACTOR AND RESISTANCE RESPONSE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 32  (4) , 457-465
Abstract
Guinea pigs developed resistance to larvae of the ixodid tick, Dermacentor andersoni, after 1 infestation. Resistant hosts were characterized by allowing significantly fewer larvae to engorge than non-resistant hosts. Larvae engorging on non-resistant hosts had a mean weight 6 times that of larvae obtained from resistant hosts at the end of a 5 day infestation. This immunologically based resistance was previously shown to have a cell-mediated and a humoral component. In an attempt to ascertain the role of complement [C] in the resistance response, cobra venom factor (CoF) was administered to guinea pigs producing prolonged (85-95%) depletion of C titers. CoF was administered during an initial infestation with tick larvae to determine if C depletion altered the acquisition of tick resistance. CoF was also administered to tick-resistant hosts in an attempt to determine if the expression of tick resistance and the development of the basophil-packed lesion, characteristic of the tick-attachment site in resistant hosts, could be altered by C depletion. CoF did not alter the acquisition of resistance when C levels were reduced during a primary infestation. C depletion of an animal which had acquired tick resistance blocked the expression of that resistance during a challenge infestation. In addition to increased numbers and weights of larvae engorging on tick-resistant animals depleted of C, the basophil packed lesion at the tick attachment site was greatly reduced. C plays an important role in the expression of tick resistance in guinea-pigs.