Modulation of Immunity by Lymphatic Dysfunction in Lymphedema

Abstract

The debilitating condition known as secondary lymphedema frequently occurs after lymphadenectomy and/or radiotherapy for the treatment of cancer. These therapies can damage lymphatic vessels leading to edema, fibrosis, inflammation and dysregulated adipogenesis, which result in profound swelling of an affected limb. Importantly, lymphedema patients often exhibit impaired immune function which predisposes them to a variety of infections. It is known that lymphadenectomy can compromise the acquisition of adaptive immune responses and antibody production; however the cellular mechanisms involved are poorly understood. Here we discuss recent progress in revealing the cellular and molecular mechanisms underlying poor immune function in secondary lymphedema, which has indicated a key role for regulatory T cells in immunosuppression in this disease. Furthermore, the interaction of CD4⁺ T cells and macrophages has been shown to play a role in driving proliferation of lymphatic endothelial cells and aberrant lymphangiogenesis, which contribute to interstitial fluid accumulation in lymphedema. These new insights into the interplay between lymphatic vessels and the immune system in lymphedema will likely provide opportunities for novel therapeutic approaches designed to improve clinical outcomes in this problematic disease.

Keywords: T-helper cells; immune function; inflammation; lymphedema; regulatory T cells.

Figure 1

Effects of immune cells on the pathogenesis of lymphedema. The diagram indicates how different immune cell types influence inflammation and other aspects of lymphedema pathology. Key molecular mediators produced by these cells types, which have been reported to drive the outcomes listed at the bottom of the figure, are indicated next to the long arrows. “Th” denotes T-helper cells, “Tregs” regulatory T cells, “IL” interleukin and “NOS” inducible nitric oxide synthase.