Successive tick infestations selectively promote a T-helper 2 cytokine profile in mice.
Several studies have revealed that T lymphocytes and cytokines play a crucial role in determining the outcome of parasitic infections in terms of protective immunity. In this study we found that Rhipicephalus sanguineus tick saliva stimulates transforming growth factor-beta (TGF-beta), and reduces interleukin-12 (IL-12) secretion by cells from normal C3H/HeJ mice. Moreover, murine lymph node cells harvested 6 days after the fourth infestation with ticks presented an 82.4% decrease in their proliferative response to concanavalin A (Con A) compared with the response of control cells. In addition, lymph node cells cultured in the presence of Con A showed a T-helper 2-type (Th2-type) cytokine profile, represented by augmented IL-4 and IL-10 and TGF-beta. On the other hand, the IL-2, interferon-gamma (IFN-gamma) and IL-12 synthesis was significantly inhibited. These results indicate that ticks may modulate the host's immune response through saliva injection. Considering that C3H/HeJ mice develop no protective immunity to R. sanguineus infestation, our results suggest that tick-induced Th2-type cytokines and a decreased proliferative response probably lead the host to a susceptible state to both tick and tick-transmitted pathogens.
Ferreira
B R
BR
Department of Immunology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
Silva
J S
JS
D000818:Animals; D018929:Cell Culture Techniques; D002455:Cell Division / Q000276:immunology; D003208:Concanavalin A / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis*; D004285:Dogs; D005260:Female; D018664:Interleukin-12 / Q000096:biosynthesis; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D012008:Recurrence; D012463:Saliva / Q000276:immunology; D013154:Spleen / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology*; D013984:Tick Infestations / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis
D016207:Cytokines; D016212:Transforming Growth Factor beta; D003208:Concanavalin A; D018664:Interleukin-12