Lymphoid tissue homing chemokines are expressed in chronic inflammation

Secondary lymphoid tissue chemokine (SLC) and B lymphocyte chemoattractant (BLC) are homing chemokines that have been implicated in the trafficking of lymphocytes and dendritic cells in lymphoid organs, Lymphotoxin-alpha (LT alpha), a cytokine crucial for development of lymphoid organs, is important for expression of SLC and BLC in secondary lymphoid organs during development. Here we report that transgenic expression of LT alpha induces inflammation and ectopic expression of SLC and BLC in the adult animal. LT beta was not necessary for induction of BLC and SLC in inflamed tissues, whereas, in contrast, tumor necrosis factor receptor-1 was found to be important for the LT alpha-mediated induction of these chemokines. The ectopic expression of LT alpha is associated with a chronic inflammation that closely resembles organized lymphoid tissue and this lymphoid neogenesis can also be seen in several chronic inflammatory diseases, including in the pancreas of the prediabetic nonobese diabetic (NOD) mouse. Expression of SLC was also observed in the pancreas of prediabetic NOD mice. This study implicates BLC and SLC in chronic inflammation and presents further evidence that LT alpha orchestrates lymphoid organogenesis both during development and in inflammatory processes.