Abstract
The role of delayedβtype hypersensitivity (DTH) to chlamydial infection has been shown to be a doubleβedged sword to the host. Reported animal and human studies have, on the one hand, shown that DTH is associated with protective immunity against chlamydial infection and, on the other hand, shown links to immunopathology. Using a murine lung infection model, we recently demonstrated that there might be two different functional types of DTH induced by chlamydial infection based on its association with cytokine patterns. Th1 type DTH is associated with protection while Th2 type DTH is associated with immunopathology. The Th2 type DTH demonstrated in IFNΞ³ gene knockout (KO) mice is characterized by eosinophil infiltration in addition to mononuclear cell infiltration that exists in Th1 DTH, observed in wildβtype C57BL/6 mice and ILβ10 KO mice. In addition, the inflammatory cells in IFNΞ³ KO mice fail to target the cellular sites of chlamydial inclusions in infected tissues and fail to clear the infection. The functional differences in Th1 and Th2 type DTH responses may account for the dual role DTH plays in chlamydial protective immunity and immunopathology. Microsc. Res. Tech. 53:273β277, 2001. Β© 2001 WileyβLiss, Inc.