TRANSITION FROM INTERLEUKIN-1-BETA (IL-1-BETA) TO IL-1-ALPHA PRODUCTION DURING MATURATION OF INFLAMMATORY MACROPHAGES INVIVO

In situ production of interleukin 1-alpha (IL-1-alpha) and IL-1-beta was investigated in Peyer's patches (PP) of mice undergoing an acute bacterial infection with Yersinia enterocolitica O8. Synthesis of IL-1-beta, as determined by immunohistochemistry, was found primarily in monocytes migrating into the inflamed PP. In comparison, synthesis of IL-1-alpha was temporarily delayed by at least 24 h and was only found in mature macrophages, which did not produce detectable levels of IL-1-beta. This indicates a transition from IL-1-beta to IL-1-alpha production during maturation of monocytes into inflammatory macrophages, and further emphasizes a dichotomy between IL-1-alpha and IL-1-beta.