For decades, neutrophils were generally regarded as the cells of innate immunity with
proinflammatory and phagocytic properties involved in a dual activity, beneficial (antimicrobial)
and detrimental (tissue damage). Importantly, until the discovery of toll-like receptors (TLRs), a
role of neutrophils in adaptive immunity was limited to the effector stage of humoral response and
phagocytosis of opsonized antigens. Moreover, in common opinion, neutrophils, as well as the entire
innate immune system, were not functionally associated with adaptive immunity. At the time
we demonstrated protein chlorination by HOCl, the major product of neutrophil MPO-halide system
enhances protein immunogenicity. Based on this discovery, we proposed, as the first, a new role for
neutrophils as APC-accessory cells involved in the induction stage of adaptive immunity. Thereafter,
we developed our theory concerning the role of neutrophils as the cells which link innate and
adaptive immunity. We proposed that protein modification by HOCl may act as a neutrophildependent
molecular tagging system, by which sentinel dendritic cells can faster recognise pathogen-
derived antigens. Contemporaneously, it was demonstrated that taurine, the most abundant free
amino acid in neutrophil cytosol and the major scavenger of HOCl, is a part of the oxidantantioxidant
network and is responsible for the regulation and termination of acute inflammation.
Moreover, it has been described, that taurine chloramine (TauCl), the physiological products of the
reaction of HOCl with taurine, show anti-microbial and anti-inflammatory properties.
In this review, the role of HOCl, taurine and TauCl in innate and adaptive immunity will be discussed.