TNF-alpha release by monocytic THP-1 cells through cross-linking of the extended V-region of the oral streptococcal protein I/II

tested the hypothesis of a conserved activation mode of monocytic THP-1 cel ls by proteins I/II expressed by several species of oral streptococci throu gh the specific role of the extended V-region. We studied the binding and m odulating activities of six proteins I/II purified from strains representin g four different species of oral streptococci, and of expression products o f polymerase chain reaction-amplified sequences encoding corresponding exte nded V-regions, We found that the different proteins I/II bound to THP-1 ce lls in a sugar-dependent mode involving the extended V-region. Furthermore, all the proteins I/II stimulated THP-1 cells to produce tumor necrosis fac tor a, indicating that these properties are not strain- or species-specific . Despite the weak: stimulation of THP-1 cells by the extended V-region alo ne, we obtained evidence that cross-linking of this region can be one of th e mechanisms involved in monocytic cell activation by proteins I/II.