Cytokines (IL-4 and IFN-γ) and antibodies (IgE and IgG2a) produced in mice infected with <i>Borrelia burgdorferi</i> sensu stricto via nymphs of <i>Ixodes ricinus</i> ticks or syringe inoculations

Mice were tolerant to tick bites during three infestations with nymphs of <i>Ixodes ricinus</i> infected with <i>Borrelia burgdorferi</i> sensu stricto. To determine whether tick bites influence the immune response against <i>B. burgdorferi</i>, we examined the production of cytokines IL-4 and IFN-γ by lymph node cells of BALB/c mice and IL-4 deficient BALB/c mice after tick inoculation versus syringe inoculation of <i>B. burgdorferi</i>. We also measured IgG2a anti-borrelial antibodies and total IgE in these mice. Results showed that BALB/c mice developed a Th2 immune response against <i>B. burgdorferi</i> after tick inoculation and a mixed Th1/Th2 response after syringe inoculation of <i>B. burgdorferi</i>. IL-4 deficient mice produced a Th1 immune response in both cases. IL-4 produced following tick bites greatly decreased the production of anti-borrelial IgG2a antibodies by comparison with the production of anti-borrelial IgG2a antibodies produced following syringe injection of <i>B. burgdorferi</i>.