生发中心(GC)的成功发展在很大程度上依赖于先天机制来放大最初的炎症级联反应。除了它们在抗原呈递中的作用,先天细胞对于循环淋巴细胞向引流淋巴结(dLN)的重定向,以最大化抗原监测是必不可少的.鞘氨醇-1-磷酸(S1P)及其受体(S1PR1-5)影响免疫的各个方面;然而,S1PR4在调节免疫反应中的作用尚不清楚。在这里,我们使用局部TH1炎症的脚垫模型来仔细监测血液中白细胞数量的变化,免疫组织,还有dLN.免疫后几小时内,中性粒细胞未能充分动员并渗入S1PR4-/-小鼠的足垫组织,从而减少了局部血管变化,认为这对于将循环细胞重定向到发炎区域是必要的。使用抗Ly6G抗体的中性粒细胞耗竭显着减少了WT小鼠dLN中早期组织水肿以及初始淋巴细胞的重定向和初始积累,而S1PR4-/-dLN的影响不明显或不明显。过继转移实验进一步证明,体内淋巴细胞归巢缺陷不是供体S1PR4-/-淋巴细胞固有的,而是归因于S1PR4缺陷宿主内的差异。S1PR4-/-小鼠中减少的细胞募集会使dLN的抗原应答淋巴细胞减少,实际上,免疫反应高峰期的dLN肥大严重减弱,在这些小鼠中具有减弱的GC和激活途径。S1PR4-/-dLN的组织学检查还显示了不发达的血管网络,白细胞束缚配体的表达减少,PNAd,在高内皮小静脉区域内,表明dLN增长不足意味着支持稳健的GC反应。因此,我们的研究表明,S1PR4可能将中性粒细胞的早期免疫调节与循环淋巴细胞的初始募集以及dLN的下游扩增和成熟联系起来,从而有助于适应性反应期间的最佳GC发展。
The successful development of germinal centers (GC) relies heavily on innate mechanisms to amplify the initial inflammatory cascade. In addition to their role in antigen presentation, innate cells are essential for the redirection of circulating lymphocytes toward the draining lymph node (dLN) to maximize antigen surveillance. Sphingosine-1-Phosphate (S1P) and its receptors (S1PR1-5) affect various aspects of immunity; however, the role of S1PR4 in regulating an immune response is not well understood. Here we use a footpad model of localized TH1 inflammation to carefully monitor changes in leukocyte populations within the blood, the immunized tissue, and the dLN. Within hours of immunization, neutrophils failed to adequately mobilize and infiltrate into the footpad tissue of S1PR4-/- mice, thereby diminishing the local vascular changes thought to be necessary for redirecting circulating cells toward the inflamed region. Neutrophil depletion with anti-Ly6G antibodies significantly reduced early tissue edema as well as the redirection and initial accumulation of naïve lymphocytes in dLN of WT mice, while the effects were less prominent or absent in S1PR4-/- dLN. Adoptive transfer experiments further demonstrated that the lymphocyte homing deficiencies in vivo were not intrinsic to the donor S1PR4-/- lymphocytes, but were instead attributed to differences within the S1PR4-deficient host. Reduced cell recruitment in S1PR4-/- mice would seed the dLN with fewer antigen-respondent lymphocytes and indeed, dLN hypertrophy at the peak of the immune response was severely diminished, with attenuated GC and activation pathways in these mice. Histological examination of the S1PR4-/- dLN also revealed an underdeveloped vascular network with reduced expression of the leukocyte tethering ligand, PNAd, within high endothelial venule regions, suggesting inadequate growth of the dLN meant to support a robust GC response. Thus, our study reveals that S1PR4 may link early immune modulation by neutrophils to the initial recruitment of circulating lymphocytes and downstream expansion and maturation of the dLN, thereby contributing to optimal GC development during an adaptive response.