Latest developments in tryptophan metabolism: Understanding its role in B cell immunity

Abstract

One of the most essential and important building blocks of life is the tryptophan amino acid. As such, the pathways surrounding its metabolism are often crucial for the maintenance of proper cell activity and homeostasis. The ratios of tryptophan to kynurenine, mainly mediated by indoleamine 2,3-dioxygenase activity, is a key parameter in the inflammation as well as immunomodulation of both aseptic and septic diseases. As a result, several studies have been published to better understand the mechanisms by which the tryptophan pathways lead to such outcomes. Many have focused on gut health and cells associated with the given environment, the majority of which constitute regulatory T cells and T helper 17 cells. However, recent studies have highlighted the role of this molecular pathway on its capacity to modulate B cells functions and humoral immunity. Accordingly, the focus of this short review is to examine the key tryptophan pathways and their impact on B cells demonstrated by those studies. A better understanding of the role of tryptophan and its metabolites is crucial for its use in disease prevention and treatments.

Keywords: Autoimmunity; B cells; Immunosuppression; Indoleamine 2,3-dioxygenase (IDO); Kynurenine; Tryptophan; Viral infection.