Patients with localized juvenile periodontitis (LJP) exhibit a decreased PMN response to chemoattractants such as C5a,IL-8, and FMLP. Previous studies from our group and others suggest a molecular alteration of the FMLP receptor as well as alterations in transmembrane signaling transmission mechanisms common to different chemoattractants. The purpose of this study is to elucidate the molecular mechanisms associated with these functional PMN defects in LJP, which will likely aid in understanding the normal function of this and similar chemotactic receptors. We have analyzed FMLP receptor DNA by Single Strand Conformational Polymorphism (SSCP) and direct DNA sequencing. Of 36 LJP patients tested, 34 exhibited altered SSCP patterns when compared to healthy controls or patients with Generalized juvenile Periodontitis (GIP). Furthermore, of the 16 LJP patients' DNA sequenced so far, 14 showed mutations in the FMLP receptor molecular when compared to healthy or GJP controls, specifically, a C more then W switch at residue position 126, and a F more then S switch at residue position 110. These changes were not part of the sequence polymorphisms observed in athe control subjects. more importantly, such mutations occurred in areas of the FMLP receptor molecule which have been implicated in ligand binding and G-protein activation. We thus propose to identify potential differences in the FMLP receptor DNA in LIP patients, to determine the extent to which these two amino acid substitutions, and possibly others, occur, and to evaluate ligand binding and G-protein activations in PMN from LJP patients exhibiting these mutations. Since the activation of neutrophils by FMLP, C5a and IL-8 is associated with transmembrane signal mechanisms common to all three agonist, it is possible that the reported decreased responses of LJP PMN to these agents may also be due to alterations of these mechanisms rather than specific receptor """"""""defects"""""""". Accordingly, we propose to analyze the response of PMN from these patients to FMLP, as well as IL-8 and C5a, examining both ligand binding and G-protein activation. Our purpose is to determine whether the observed functional defect is associated with a particular agonist, or with activation mechanisms common to all three, and to relate these to the mutations we observed in these patients. Finally, we would like to confirm any functional effects t he mutations found in the LJP patients may have in PMN function by testing such mutations in a well-defined, in vitro mammalian recombinant expression system. We feel that this study provides a unique opportunity to correlate normal PMN function with studies on PMN from a disease state. The mutations found in LJP patients may help elucidate residues of the FMLP receptor involved in cell activation. While studies of th normal have historically been used to study disease, in this case, the disease itself may provide an excellent model to study normal PMN function.
| Boehm, Tobias Konrad; Sojar, Hakimuddin; Denardin, Ernesto (2010) Concentration-dependent effect of fibrinogen on IgG-specific antigen binding and phagocytosis. Cell Immunol 263:41-8 |
