Characterization of the adaptive immune response following immunization in pregnant sows (Sus scrofa) kept in two different housing systems.

Housing conditions might differentially affect the adaptive immune responses to a neoantigen in pregnant sows with possible consequences for the success of vaccinations. Therefore, this study aimed at characterizing antigen-specific T cell and B cell responses of pregnant sows (German Landrace) either housed in a social group (GP; n = 22) or confined in individual gestation crates (CR; n = 11). All sows were immunized with the neoantigen keyhole limpet hemocyanin (KLH) 7 and 5 wk prepartum. Blood samples were taken 7, 6, 4, and 2 wk prepartum, thus before and after the first as well as second immunization. This study aimed at identifying both the resulting cellular as well as humoral KLH-specific immune response in the pregnant sows. We therefore analyzed total IgG and anti-KLH IgG concentrations and the KLH-specific lymphocyte proliferation as well as the KLH-specific production of the T helper cell type 1 (TH1)-related cytokines tumor necrosis factor (TNF) α and interferon (IFN) γ in main T cell subsets before and after the immunization. Anti-KLH IgG titers significantly increased during the experimental procedure (P < 0.001) reflecting the activation and differentiation of KLH-specific B cells on immunization. However, CR-housed sows showed greater anti-KLH IgG concentrations compared to GP-housed sows (P < 0.05). Keyhole limpet hemocyanin-specific TNFα-producing cytotoxic T cells (CTL) and T helper (TH) cells were detectable in CR-housed sows not before the second immunization (both P < 0.05), whereas those cells were detectable already after the first immunization in GP-housed sows (CTL: P < 0.01 and TH: P < 0.05). Similarly, KLH-specific TNFα/IFNγ-double producing CTL and TH cells were detectable earlier in GP-housed sows than in CR-housed sows (both P < 0.05). Keyhole limpet hemocyanin-induced lymphocyte proliferation and total IgG concentrations were not affected by the housing system. Our results show that housing conditions affect the adaptive immunity to a neoantigen in pregnant sows. Whereas GP housing of pregnant sows induced a rather TH1-mediated cellular response, individual housing in CR resulted in a T helper cell type 2 (TH2)-pronounced humoral response to KLH. The greater anti-KLH IgG concentration and the delayed activation and differentiation of KLH-specific TH1 cells in CR-housed sows support the hypothesis of a shifted TH1:TH2 ratio in individually housed sows of this study. We presume differences in the stressfulness of the housing system to be mainly responsible for the occurring effects.