Mitogenic activity of Actinomyces viscosus. II. Induction of DNA and immunoglobulin synthesis in rabbit B lymphocytes

Genetic control of mitogen-induced B-cell hyperproliferation in SM/J mice

Previous studies have shown that B cells from SM/J mice exhibit hyperproliferative responsiveness to several bacterial-derived B-cell mitogens. This hyperresponse trait was found to be under autosomal, polygenic control by non-H-2 genes. We have now estimated the number of genes involved by statistical analysis of the proliferative responses of splenocytes from SM/J and low-responder C57BL/6J strains, and progeny from the (B6 X SM)F1, F2 and (F1 X B6) crosses. The number of loci involved was ascertained using two different statistical approaches. An estimate of two loci was determined using chi-squared statistics. The second approach, based on an additive model in the natural log scale, also pointed to a lower bound of two genes. We conclude that the hyperresponse to B-cell mitogens in SM/J mice is determined by two autosomal genes which are not linked to the H-2 major histocompatibility complex.

Mitogen-induced hyperproliferation response of peripheral blood mononuclear cells from patients with severe generalized periodontitis: lack of correlation with proportions of T cells and T-cell subsets

Severe generalized periodontitis (SGP) is a localized inflammatory disease which differs clinically from common periodontitis in that it leads to remarkable extensive alveolar bone loss in relatively young adults. There is evidence that B-cell responses to bacterial substances may play a major role in the pathogenesis of this disease. In the present report, we show that a B-cell mitogen from Actinomyces viscosus (AVIS) bacteria provokes a hyperproliferation response of peripheral blood mononuclear cells (PBMNC) from these patients. In addition, AVIS-stimulated PBMNC from SGP patients proliferate for longer periods in culture than do PBMNC from control subjects. There were, however, no differences between patients and controls in the numbers of immunoglobulin-secreting cells in these cultures as determined by an indirect plaque-forming cell assay. The possibility that differences in numerical proportions of regulatory T-cell subsets may play a role in the mitogen-induced hyperproliferation phenomenon is examined. PBMNC were stained with fluorescein isothiocyanate-conjugated monoclonal antibodies OKT3, OKT4, and OKT8 in order to identify, respectively, total T cells, helper/inducer, and suppressor/cytotoxic subsets. Flow cytometric analysis of such specifically stained cell preparations from 14 control subjects and 14 SGP patients did not reveal any significant differences between the proportions of total T cells or T-cell subsets of the two groups. Furthermore, there were no statistically significant correlations between the magnitude of proliferation responses and the proportions of total T cells or either of the T-cell subsets.

Polyclonal antibody-forming cell activation and immunomodulation of the in vitro immune response induced by streptococcal extracellular products

The capacity of three different extracellular streptococcal products to induce polyclonal activation of precursors of plaque-forming cells (PFC) was investigated. The gamma fraction (pI = 4.2), previously shown to be only weakly mitogenic, was the most potent activator of rabbit and mouse immunoglobulin-secreting cells. The polyclonal stimulation induced by the two other fractions (kappa: pI = 4.8 and epsilon: pI = 10.3), shown to be mitogenic in both systems, was only observed in the rabbit system. Using these fractions, the in vitro immunomodulation of the anti-sheep red blood cell immune response was also investigated. Both gamma and epsilon fractions were shown to possess adjuvant properties, whereas the kappa fraction was a suppressor of the specific immune response. It appears, therefore, that the diversified immunological activities observed with extracellular streptococcal products can be dissociated and belong to different entities.

Role of macrophages in the lymphocyte response to Actinomyces viscosus

Macrophage cooperation has been considered necessary for lymphocytes to express a variety of their differentiated functions. We attempted to characterize macrophage-lymphocyte cooperation in response to a known periodontal pathogen. Actinomyces viscosus T14V. Using adherent murine cells and subpopulations of splenocyte cultures, we assessed the effect of A. viscosus T14V fractions on lymphocyte proliferation. We determined that (i) various fractions of A. viscosus induced different proliferative responses; (ii) the physical state of the A. viscosus component determined the degree of dependence on adherent cells for proliferation; (iii) the proliferative response to supernatants of sonicated A. viscosus involved interaction among adherent cells and T and B cells; and (iv) the effects of adherent cells on the proliferative response were due to cell-to-cell interactions.

Differences in lymphoproliferative responses to the bacterium Actinomyces viscosus in various mammalian species

A water-soluble extract of Actinomyces viscosus (AVS) was tested for its capacity to induce DNA synthesis in lymphocytes from man, monkeys, mice and guinea pigs. The results indicated that the AVS induced an in-vitro lymphoproliferative response, as assessed by tritiated thymidine incorporation, in mouse-spleen cells, in the majority of human peripheral blood samples tested and in macaque monkey spleen cells. The AVS also elicited a blastogenic response from spleen, lymph node and peripheral blood lymphocytes from guinea pigs immunized with A. viscosus. The AVS did not elicit a lymphoproliferative response from human-cord blood cells, monkey peripheral blood lymphocytes, or peripheral blood and spleen lymphocytes from non-immunized guinea pigs. Thus there was a difference in the ability of A. viscosus to induce DNA synthesis in lymphocytes from the different animal species tested.

Immunologic tolerance to collagen and glycosaminoglycan components of scleral allografts in humans. Evidence for T cell suppression

Unfractionated peripheral blood lymphocytes (PBL) and the T and B cell fractions of PBL from four patients who had received scleral allografts, and fractions from four control subjects were tested in vitro for proliferative responsiveness to collagen and glycosaminoglycan-enriched extracts of allogeneic sclera. None of the unfractionated lymphocyte cultures (patients and controls) were responsive to the scleral extracts. However, B-enriched lymphocyte cultures from one patient and two control subjects did respond to the scleral extracts, although there was considerable individual variation in the magnitudes of these responses (stimulation indices ranging from 1.5 to 11.5). In contrast, the DNA-synthesis response of T cells to scleral extracts was strongly suppressed. Furthermore, T cells pre-exposed for 24 hours to scleral collagen were capable of suppressing B-cell responsiveness to mitogens in autologous mixed lymphocyte cultures. Our findings confirm the lack of apparent adverse immunologic responsiveness to scleral allografts in humans as reported by others. It is possible that immunological tolerance to the scleral allografts is due to a suppressor T-cell mechanism which is triggered by scleral collagen.

Immune responsiveness of SM/J mice. Cellular characteristics and genetic analysis of hyperresponsiveness to B cell mitogens

We tested the proliferative responses of splenocytes from a panel of inbred mouse strains to AVIS, a B cell mitogen from Actinomyces viscosus bacteria. The SM/J strain was found to exhibit severalfold higher responsiveness than any of the other strains. SM/J splenocytes were also hyperresponsive to the B cell mitogens lipopolysaccharide, dextran sulfate, and purified protein derivative of tuberculin, but responsiveness to the T cell mitogen phytohemagglutinin was normal. (B6 X SM)F1 and F1 x B6 backcross mice were tested for AVIS and lipopolysaccharide responsiveness, and it was determined that hyperresponsiveness was under polygenic, autosomal, non-H-2-linked gene control. Genetic control of response to B mitogens in SM/J mice appears to be expressed solely through the B lymphocyte because removal of T lymphocytes or macrophages did not reduce the magnitude of responsiveness in vitro. SM/J mice may provide a useful model for testing questions regarding B cell triggering, differentiation, and function, and to examine the genes involved with B cell proliferation.