The response of phagocytic leukocytes to mucosal infection with N. gonorrhoeae (GC) and C. trichomatis (CT) is an important aspect of both the protective immune response to infection and the development of pelvic inflammatory disease (PID). We hypothesize that innate immune responses determine the extent of GC and CT invasion and the nature of histopathological changes which result from infection. Within hours to days of mucosal infection, phagocytic leukocytes populate the genital tract. The initial movement of phagocytes from the bloodstream to the tissues, and the initial stages of bacterial killing, involve complex interactions of the leukocyte integrin CR3 (CD11b/CD18) with its ligands. CRC functions as a phagocytic receptor for Gram-negative bacteria and activated complement fragments. We believe that CR3 plays a key role during the process of bacterial invasion, limiting the extent of infection, possibly at the price of exacerbating host injury. During the initial stages of invasion, LPS present in the outer membrane of GC and CT activate the production of inflammatory cytokines by both professional and non-professional phagocytic cells via LPS receptors. Thus, proteins which enable or enhance recognition of LPS may be important anti-bacterial defenses. For example, LPS binding protein (LBP) and soluble CD14 (sCD14), which are present in blood and genital tract secretions, bind Gram-negative bacteria, and have been shown to enhance the binding of bacteria to phagocytic leukocytes. We hypothesize that innate immune recognition of GC and CT is enhanced by opsonization with Scd14. We propose to address the role of innate immune responses to GC and CT infection by examining the role of these LPS receptors CR3 and CD14 in the host response to urogenital infection with thee pathogens. We will first determine the levels of LBP and sCD14 in human clinical specimens, including patients with GC and CT infection. Then, we will examine if LBP and sCD14 opsonize GC and CT both in vitro and in vivo. CR3- mediated signal transduction will be explored using newly available CD14+ cell lines with defects in the CD14 signal transduction pathway. Finally, the role of CR3 in CT mucosal infections will be examined through the use of a genetically engineered """"""""knockout"""""""" mouse deficient in the expression of CR3. Mice will be tested in a lower tract infection model of PID in the belief that the targeted gene deletion will compromise innate immune resistance to CT. We believe these studies will add important new knowledge about the role of innate immunity in the defense of GC and CT infections.
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