Age-dependent distribution and size of lymphatic nodules as components of extrahepatic bile duct-associated lymphatic tissue in domestic swine - a micromorphometric study

Due to the biological and immunological similarity between pigs and humans, pigs are used in medical research. Many morphological studies regarding the structure of the components of mucosal associated lymphatic tissue have been performed in animals including pigs as well as in humans. However, no any information about the existence of extrahepatic bile duct-associated lymphoid tissue (EHBDALT) is available in pigs. The aim of this work was to study the distribution and size of lymphatic nodules in the wall of extrahepatic bile ducts of immature and mature pigs in order to describe the structure of EHBDALT as component of mucosa-associated lymphoid tissue. It was found out that EHBDALT consisted of diffuse lymphatic tissue, solitary and aggregated lymphatic nodules. In 2-month-old pigs, diffuse lymphatic tissue predominated but single lymphatic nodules were found as inactive homogenous encapsulated aggregates of lymphocytes. In mature animals, diffuse lymphatic tissue, primary and secondary nodules were observed. The present micromorphometric study allowed evaluating the age-dependent distribution and size of lymphatic nodules in porcine extrahepatic bile ducts. It provides original data on the presence and age-dependent structure of bile duct MALT in domestic pigs.