The cellular transfer of immunity to Trichostrongylus colubriformis in an isogenic strain of guinea-pig. II. The relative susceptibility of the larval and adult stages of the parasite to immunological attack.

Cells obtained from mesenteric lymph nodes of highly inbred guinea-pigs (Heston strain) resistant to were injected into virgin animals of the same genotype. The adoptively immunized recipients were challenged with 1000 larvae 4 days after transfer and slaughtered at intervals which correspond to critical times in the development of the parasite. Differential worm counts carried out on specimens of intestine showed that a sharp decline in the number of parasites occurred between days 7 and 9. This period corresponds to the time required for the parasite to develop to the fourth larval stage. Variation of the time interval between cell transfer and challenge showed that immune cells transferred on the day of challenge and on days 4, 6 and 8 after challenge inhibited the development of infection to patency, while cells injected on day 10 were without effect. This observation confirmed that the fourth larval stage of the parasite is uniquely susceptible to the immunological attack initiated by the transferred cells and showed that these cells are effective within 24–48 hours after injection. This latter finding excludes the possibility of active participation in the response by the recipient. Resistance can be transferred by spleen cells and by cells obtained from lymph nodes other than the mesenteric nodes which drain the site of infection. However the local nodes are more effective and resistance was regularly transferred with as few as 10 × 10 cells injected intravenously.