ACQUIRED-RESISTANCE TO TICKS .4. SKIN REACTIVITY AND INVITRO LYMPHOCYTE RESPONSIVENESS TO SALIVARY-GLAND ANTIGEN

Abstract

Guinea-pigs developed resistance to the ixodid tick, Dermacentor andersoni, after 1 infestation. Resistance was characterized by guinea-pigs allowing significantly fewer larvae (10-20%) to engorge during a 2nd infestation than during an initial infestation (90-99%). The immunological nature of guinea-pig resistance to D. andersoni larvae is confirmed. There seems to be a cell-mediated immune component to the resistance. An antigen isolated from the salivary glands of adult female D. andersoni stimulated in vivo delayed skin reactivity when administered intradermally to tick-resistant guinea-pigs. Salivary gland antigen (SGA) initiated in vitro lymphocyte blastogenesis when added to cultures of lymph node cells from tick-resistant hosts. Antigen-specific responsiveness of lymphocytes to SGA occurred over a period 2-4 days after the termination of an initial infestation with tick larvae until the termination of a 2nd infestation. Basophils first appeared at tick attachment sites at the time when antigen-specific lymphocyte responsiveness was first significant. Peak responsiveness occurred 24 h after the initiation of a 2nd larval infestation at a time when large numbers of basophils were attracted to the tick attachment site. Tick infestation might induce a degree of immunosuppression in the host.