Blastogenic responses of lymphocytes from sheep experimentally infected with Trichostrongylus colubriformis

Thirty 15-month-old ewes were randomly allocated to three groups of 10 sheep each. One group was given a single infection of 60,000 T. colubriformis 3rd stage larvae (L3). The second group 2 was infected orally with 20,000, 40,000 and 60,000 L3 T. colubriformis at 21 day intervals and 21 days after the third dose the sheep were treated with Oxfendazole. Seven days later Groups 1 and 2 sheep were challenged with 60,000 L3 T. colubriformis. The third group was left as uninfected controls. All sheep were bled at weekly intervals and the blastogenic responses to Con A, PHA, PWM and LPS of peripheral blood lymphocytes were evaluated using tritiated thymidine incorporation into DNA. When lymphocytes were cultured with Con A, PHA, PWM or LPS, a progressive decrease of blastogenic activity was observed up to 35 days after a single infection of sheep. In multiple infected sheep, the blastogenic responses to the mitogens were generally depressed from the second infection or shortly thereafter with a return to control levels observed only with LPS. Non-mitogen stimulated lymphocytes from single and multiple infected sheep showed significantly increased blastogenic activity on 35 day after each infection. The data indicate that this type of infection with T. colubriformis may have led to activation of peripheral lymphocytes, coinciding with diminished T-cell responsiveness to the mitogens.