Nasal-associated lymphoid tissue (NALT): frequency and localization in young children.

In mucosal immunology nasal-associated lymphoid tissue (NALT) is taken as a constitutive structure of the nasal immune system and as a target tissue in strategies of local defence and an induction site for vaccination. These concepts are based on findings in rodents, but it has not been investigated systematically whether NALT also is present in humans and if so in which amount and localization. In a postmortem study the presence of NALT in humans is documented as a morphologically distinct structure additional to the lymphoid structures of the Waldeyer's ring. Human nasal tissue blocks of 150 children who had died in the first two years of life either of sudden infant death (n = 109) without signs of respiratory tract infections or of different traumatic (n = 22) and natural causes of death (n = 19) were obtained using a specific autopsy-technique and were investigated systematically using histology. Clearly in contrast to rodents human NALT was found disseminated in the nasal mucosa with typical morphological features in 38% of all children, mainly in the middle concha, with similar morphology and frequency in the examined groups. No correlation was found between the presence of NALT and the cause of death and especially the grade of inflammation in general. Therefore, NALT might be the morphological basis for inhalative vaccination strategies in young children and play a role in mucosal host defence.