"α2, 8連結之雙唾液酸結構在體液免疫中的角色以及與唾液酸結合之似免疫球蛋白凝集素E型的相互作用"

Abstract

The role of increasing α2, 8-diSialyl motif synthesized by ST8Sia VI on differentiating B cell surface was unclear. Additionally, it is reported that there is only Siglec-E that can recognize α2, 8-diSialyl motif. We have previously established B cell specific ST8Sia VI knockout (cKO) mice. Our preliminary results showed that ST8Sia VI cKO mice produced higher levels of IgM after immunization. Therefore, in this thesis, we focused on which subsets of B cells contributed to function of α2, 8-diSialyl motif and whether the interplay of Siglec-E was involved. First, we generated that Rbpj and ST8Sia VI B cell-specific double knockout mice, which featured marginal zone B (mzB) cells and α2, 8-diSialyl motif deficiency. These mice showed higher IgM production at the levels similar to those produced by ST8Sia VI cKO mice upon TI antigen immunization. Furthermore, sorted follicle B (foB) cells and B1 cells, but not mzB cells, from ST8Sia VI cKO mice showed stronger activation after stimulation with either LPS or anti-IgM. We also generated SS-KO mice, whose ST8Sia VI and Siglece were deleted, to determine the interaction of Siglec-E and α2, 8-diSialyl motif. We found that SS-KO mice still produced higher amounts of antigen specific IgM than wild type (WT) mice did upon NP-Ficoll immunization, but that the levels of antigen specific IgM in SS-KO mice were similar to that in WT mice after NP-LPS immunization. These results suggested that the interaction between α2, 8-diSialyl motif and Siglec-E may be involved in TLR4 signaling. Furthermore, we found that the higher activation of foB cells from ST8Sia VI cKO mice were compromised after co-cultured with macrophages or neutrophils form Siglece KO mice after LPS stimulation. On the other hand, both Siglece KO and ST8Sia VI cKO B1 B cells were activated better after LPS stimulation. In conclusion, α2, 8-diSialyl motif not only plays an inhibitory role on foB cells but also acts through Siglec-E in both cis- and trans- manners on B1 and foB cells separately.