nasalassociated

Nasal-associated lymphoid tissue, often abbreviated NALT, refers to mucosa-associated lymphoid tissue located in the nasal passages and upper pharynx as part of the mucosal immune system. It acts as an inductive site for immune responses to inhaled antigens and helps coordinate local and systemic immunity. In humans, NALT is not a single hollow organ but consists of diffuse lymphoid aggregates within the nasal mucosa and the pharyngeal-associated lymphoid tissue, including the adenoids (pharyngeal tonsils) and scattered lymphoid follicles along the nasal passages. In some species, such as mice, NALT is more clearly defined as a discrete lymphoid structure along the nasopharyngeal roof.

NALT contains the cellular components typical of mucosal lymphoid tissue, including B and T lymphocytes, dendritic cells, macrophages, and specialized M cells that sample antigens from the nasal lumen. Upon antigen exposure, these cells coordinate germinal center reactions, leading to B cell activation, class switching to IgA, and formation of memory B and T cells. Secretory IgA produced by mucosal plasma cells provides targeted defense by neutralizing pathogens at the nasal surface, while NALT also contributes to broader immune responses and tolerance.

Developmentally, NALT arises postnatally and is shaped by environmental exposure and microbial communities. Its activity can be influenced by age, chronic inflammation, or allergic states, with implications for mucosal immunity. Clinically, NALT is a focal point for intranasal vaccines designed to elicit robust mucosal IgA and systemic responses. Research into NALT informs understanding of respiratory immunity, vaccine delivery, and mucosal immunology more broadly.