T lymphocytes negatively regulate lymph node lymphatic vessel formation.

Lymph node lymphatic vessels (LNLVs) serve as a conduit to drain antigens from peripheral tissues to within the lymph nodes. LNLV density is known to be positively regulated by vascular endothelial growth factors secreted by B cells, macrophages, and dendritic cells (DCs). Here, we show that LNLV formation was negatively regulated by T cells. In both steady and inflammatory states, the density of LNLVs was increased in the absence of T cells but decreased when T cells were restored. Interferon-γ secretion by T cells suppressed lymphatic-specific genes in lymphatic endothelial cells and consequently caused marked reduction in LNLV formation. When T cells were depleted, recruitment of antigen-carrying DCs to LNs was augmented, reflecting a compensatory mechanism for antigen presentation to T cells through increased LNLVs. Thus, T cells maintain the homeostatic balance of LNLV density through a negative paracrine action of interferon-γ.