Polyclonal induction of IgG antibody forming cells by stimulation with Actinomyces viscosus T14V

Lipopolysaccharides from Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans promote osteoclastic differentiation in vitro

Bacterial lipopolysaccharides possess bone-resorbing activity. Here, lipopolysaccharides from three putative periodontopathic bacteria were examined for effects on osteoclast-like cell formation of bone marrow cells from lipopolysaccharide-responsive C3H-HeN and non-responsive C3H/HeJ mice. The bone marrow cells were cultured with or without various doses of lipopolysaccharide in the presence of 1,25-dihydroxyvitamin D3 and dexamethasone. These lipopolysaccharide preparations significantly increased the number of osteoclast-like cells formed in the culture of C3H/HeN marrow cells; the same as lipopolysaccharides from Escherichia coli and a synthetic lipid A with E. coli-type structure (LA-15-PP), at doses from 0.1 to 1 microgram/ml. This stimulating effect of each lipopolysaccharides was uniformly abrogated by the addition of polymyxin B at 5 micrograms/ml. All the lipopolysaccharide and the synthetic lipid A had no effect on osteoclast formation of the C3H/HeJ marrow cells, whereas lipopolysaccharide from Porphyromonas gingivalis and Prevotella intermedia showed significant mitogenic activity on C3H/HeJ spleen cells. It seems likely that the activity of lipopolysaccharides to augment osteoclast-like cell formation in the bone marrow cell cultures is derived from a common structure of the lipid A portion.

Autoimmunity to collagen in adult periodontal disease: immunoglobulin classes in sera and tissue

The immunoglobulin class distribution of antibody to human collagen type I has been examined in sera and gingival extracts from patients with adult chronic periodontitis. Tissue extracts were made either by simple washing or ultrasonication. With either method, IgG and IgA antibodies to collagen were present in higher concentration in tissue extracts than in autologous serum when adjustment was made for dilution differences. No significant differences were found for IgM antibodies. Antibodies to human collagen type I are usually "natural antibodies" of the IgM class and, therefore, our findings suggest a class switch to IgG in inflamed gingivae, presumably due to prolonged antigenic stimulation.

The function of gingival lymphocytes on the establishment of human periodontitis

Human periodontitis has been confirmed to be an IgG plasma cell-rich lesion. However, we also detected many T cells, both CD4-positive and CD8-positive cells, in periodontal lesions. Some of these T cells expressed HLA-DR (la-like) antigen on their surfaces, and the proportion of HLA-DR+ cells was approximately equal in both CD4+ and CD8+ cell populations (Okada et al., 1983, 1984). Consequently, both helper and suppressor T cells were believed to participate in the establishment of periodontal lesions.

On the other hand, B cells were thought to be activated polyclonally in periodontal lesions, because a variety of periodontal florae possessed polyclonal B-cell-activating activity. We demonstrated that Actinomyces viscosus T14V stimulated mouse spleen B cells polyclonally and induced many IgM-producing cells but few IgG-producing cells. Moreover, IgG-producing cells were differentiated from only surface IgG-positive B cells but not from surface IgG-negative B cells-namely, surface IgM- or IgA-positive B cells (Harada et al., 1988). These results suggested that memory B cells, which had already been primed with appropriate antigens, might migrate into periodontal lesions, and then be activated polyclonally and develop into IgG-producing cells.

The periodontal lesion could, therefore, be induced by the interactions of immunoregulatory mechanisms of T cells and polyclonal B cell activity of periodontal florae. In fact, L3T4-positive T cells (helper-inducer T cells) enhanced IgG synthesis of mouse spleen B cells which had been activated with T-independent B cell activators such as LPS and A. viscosus preparations (Okada et al., 1987; Ito et al., 1988). We hypothesized from the above results that autoreactive T cells recognized the increasing self-MHC class II(Ia) antigen on B cells which had been activated with polyclonal B cell activators, and then produced soluble factors, which could enhance IgG synthesis of these B cells. Autoreactive T cells as well as PBAs, thus, may play an important role in the establishment of the IgG plasma cell-rich periodontal lesion.