Cytokine responses of C3H/HeN mice infested with Ixodes scapularis or Ixodes pacificus nymphs

Lyme borreliosis, caused by Borrelia burgdorferi, is transmitted by Ixodes scapularis in the eastern and midwestern United States and by Ixodes pacifi cus in the far-Western United States. Studies have shown that infestation w ith I. scapularis nymphs modulates host cytokine production; however, the i nfluence of I. pacificus infestation on host cytokines remains uninvestigat ed. This study demonstrated how repeated infestations with pathogen-free I. scapularis or I. pacificus nymphs affects the production of the macrophage cytokines IL-1 beta, IL-6 and tumour necrosis factor-alpha and the T lymph ocyte cytokines IL-2, IL-4, IL-5, IL-6, IL-10 and IFN-gamma by C3H/HeN mice . Female mice were infested once or twice with pathogen-free I. scapularis or I. pacificus nymphs, with a 14-day tick-free period between exposures. A fter each infestation, tick biology parameters were assessed and macrophage and T lymphocyte cytokine production measured by antigen capture ELISA. Ac quired resistance to tick feeding did not develop after infestation with ei ther tick species. Differences in cytokine production were observed between infested and noninfested mice, and between mice infested with either I. sc apularis or I. pacificus nymphs. Infestations polarized cytokine production rewards a Th2 cytokine profile, with suppression of pro-inflammatory Th1 c ytokines. This pattern of cytokine production is more pronounced for I. pac ificus infested mice.