Studies on Delayed (Cellular) Hypersensitivity in Mice Infected with Trichinella spiralis. V. Tests in Recipients Injected with Donor Spleen Cells 1, 3, 7, 14, or 21 Days before Infection

Abstract

Three experiments are described. In the first, mice were injected twice into the footpads with an antigen prepared from larvae and mixed in equal volume with Freund's complete adjuvant. After an infection with T. spiralis, these mice harbored significantly fewer adult worms than noninjected controls thereby proving the immunizing effectiveness of the two antigen injections. In the last 2 experiments, donor mice, treated as the experimentals in the first experiment, were killed to collect spleen cells for transfer into recipients, which were challenged with T. spiralis 1, 3, 7, 14, or 21 days after transfer of the cells. The counts of adult worms in these recipients and their respective controls were not significantly different in the case of the 1-day and 3-day groups, but the 7, 14, and 21-day recipients harbored significantly fewer worms than their controls. On the basis of these results, it is concluded that the 2 injections of this antigen preparation produced effects that caused a significant expulsion of worms after challenge, and that the spleen cells from mice treated in this way were responsible for a similar effect noted in recipients challenged as early as 7 days after cell transfer. It was shown recently that recipient mice injected with spleen cells from artificially sensitized donors 21 days before infection with T. spiralis eliminated significant numbers of adult worms as shown by counts made 12 days after infection (Larsh et al., 1969). The 3-week period between transfer of cells and challenge was used for the reason that it was effective in earlier studies with peritoneal exudate cells (Larsh et al., 1964b, 1966) and lymph node cells (Larsh et al., 1964a). However, it requires a relatively brief period after transfer of sensitized lymphoid cells to demonstrate sensitivity in recipients. In fact, as shown by studies in guinea pigs sensitized with a crude saline extract of T. spiralis larvae, the optimal latent period for demonstrating delayed skin reactions in recipients was 3 days after transfer of lymph node cells (Kim et al., 1967). In view of this, and the obvious advantages of a shorter latent period in our studies with mice, it was decided to test the immunity in recipients infected 1, 3, 7, or 14 days after transfer of spleen cells from artificially sensitized donors. The 21-day period also was included as a check on previous results. Received for publication 26 March 1970. MATERIALS AND METHODS The Swiss white mice used in this study were a strain that had been randomly bred in our laboratory throughout the year for more than 27 years. The strain of T. spiralis and the methods for isolating larvae for infections and for recovering adult worms after challenge were those used by Larsh and Kent (1949). The antigen(s) for the sensitization of donors was made from larvae of