Th2 polarization of the immune response of BALB/c mice to Ixodes ricinus instars, importance of several antigens in activation of specific Th2 subpopulations

BALB/c mice were infested with Ixodes ricinus larvae, nymphs or adults. Exp ression of IL-4 and IFN-gamma mRNA in axillary and brachial draining lymph node cells were measured by competitive quantitative reverse transcription- polymerase chain reaction 9 days after the beginning of primary-infestation . IL-4 mRNA was always higher than that of IFN-gamma mRNA for all tick inst ars. Moreover, IL-4 mRNA expression progressively increased during nymphal primary-infestation with a high burst of expression 7 days after the beginn ing of infestation. No evolution of IFN-gamma mRNA expression was detected. Draining lymph node cells of infested BALB/c produced higher level of IL-4 than IFN-gamma following in vitro restimulation with adult tick saliva, sa livary gland extract (SGE) or with five selected different chromatographic fractions of SGE. Anti-tick IgG1 antibodies but no IgG2a were detected in B ALB/c pluri-infested with I. ricinus nymphs, which confirmed the Th2 polari zation of the immune response.