Effects of endogenous and exogenous inhibitors on the incorporation of labeled precursors into DNA by human mononuclear cells

Spontaneous lymphocyte proliferation in severe periodontal disease: role of T and B cells

Spontaneous proliferation of T cells, B cells and unseparated lymphocytes was studied in patients with severe periodontal disease and control subjects. In the patient group only, spontaneous lymphocyte proliferation was reduced, whereas B cell proliferation was enhanced. The findings offer further support for the existence of a disturbance in immune regulation in patients with severe periodontal disease.

The significance of 3H-thymidine degradation in cell culture experiments with special reference to rheumatoid arthritis

The degradation of 3H-thymidine under various cell culture conditions was analysed. It was found that a half of 3H-thymidine was degraded to 3H-thymine during 24 hours in PHA stimulation of blood lymphocytes. A control culture in which PHA was not added also caused 3H-thymidine degradation. 3H-thymidine degradation was prevented by adding 5-nitrouracil to the incubation medium at a concentration of 0.577 mg/ml. At the same time 5-NU increased 3H-thymidine incorporation into lymphocytes by 47%. 5-NU also eliminated the inhibitory effect of rheumatoid arthritis synovial tissue eluate on PHA stimulation. In addition 5-NU and nonradioactive thymine increased the 3H-thymidine labelling index of fresh rheumatoid arthritis synovial membrane biopsies, and also more of the isotope was accumulated in the individual cells of the membrane. These studies demonstrate that 3H-thymidine degradation is an important phenomenon in cell cultures and that it can be prevented effectively by using 5-nitrouracil with 3H-thymidine.

Effect of periodontal therapy on spontaneous lymphocyte response and neutrophil chemotaxis in localized and generalized juvenile periodontitis patients

The etiology and pathogenesis of juvenile periodontitis may involve dysfunctions of the host response. In particular, the neutrophil and the lymphocyte have been implicated in the disease. The purpose of the present study was to examine the in vitro spontaneous lymphocyte response and neutrophil chemotaxis in populations of localized juvenile periodontitis (LJP) and generalized juvenile periodontitis (GJP) patients and age- and sex-matched healthy subjects (HS). These laboratory values were also evaluated immediately following and 1 year after periodontal therapy. The results show that spontaneous lymphocyte responses reflecting the autologous mixed lymphocyte reaction (AMLR) are depressed for GJP patients. The decreased AMLR in the GJP group appears to represent an abnormal T-cell function which may reflect activity of the periodontal lesion. LJP patients have an increased AMLR response, although it was not statistically significant. 1 year following active periodontal therapy, spontaneous lymphocyte responsiveness returned to normal in most GJP patients. The increased spontaneous lymphocyte responsiveness of LJP patients was not changed either immediately following active periodontal therapy or 1 year later. LJP and GJP patients exhibited a neutrophil chemotaxis defect when compared to cells from HS. This neutrophil defect was still observed 1 year following active therapy.

Immunologic profile of juvenile periodontitis. I. Lymphocyte blastogenesis and the autologous mixed lymphocyte response

Studies of blastogenesis of lymphocytes in culture from juvenile periodontitis (JP) patients have been inconclusive. Experiments demonstrating differences in lymphocyte blastogenesis to preparations of putative periodontopathogens in JP and phytohaemagglutinin (PHA) were performed. Variables in the blastogenesis assay system recently reported were controlled which included using a range of cell and activator concentrations, incubation times of 3, 5 and 7 days, conical-bottomed microtest wells and chemical inhibitors during labeling of DNA which permits accurate assessment of lymphocyte blastogenesis. Using these modified culture conditions, stimulated lymphocytes of localized (LJP) and generalized (GJP) forms of JP patients did not differ significantly from stimulated lymphocytes of healthy subjects in counts incorporated, stimulation index, incubation time, cell concentration or activator dose required for maximal blastogenesis to bacterial preparations of Actinobacillus actinomycetemcomitans (Y-4), Bacteroides gingivalis, Capnocytophaga ochraceus, Fusobacterium nucleatum, Streptococcus sanguis and Treponema denticola. Unstimulated lymphocyte cultures reflecting the autologous mixed lymphocyte response (AMLR) were increased for LJP compared to healthy subjects although not statistically significant. Unstimulated lymphocyte cultures of GJP were decreased compared to healthy subjects and LJP (P less than 0.05). These observations indicate that GJP patients may have abnormalities in T- and B-lymphocyte regulatory mechanisms.

An improved method for assessing the incorporation of labeled precursors into DNA by human mononuclear cells

The blastogenic responsiveness of activated lymphoid cells is usually assessed in vitro by measuring the incorporation of radioactive thymidine or iododeoxyuridine, a thymidine analog, into DNA. The accuracy of this method is compromised by the presence in activated and unactivated lymphocytes and in some of the substances used to activate them, of degradative enzymes which compete with DNA synthetase, the incorporation efficiency of exogenous precursor is inherently low. We have done studies aimed at improving both the efficiency and the accuracy of the assay system by selectively inhibiting the enzymes responsible for thymidylate synthesis de novo and DNA precursor degradation. Culture conditions were investigated and potential inhibitors were tested using human peripheral blood mononuclear cells activated with phytohemagglutinin. Nucleoside-degrading activity of mammalian and bacterial cells is due largely to nucleoside phosphorylases, enzymes that require orthophosphate for activity. We partly inhibited DNA precursor degradation by lowering the phosphate concentration in the culture medium and lowering the pH, thereby reducing the orthophosphate concentration. To reduce precursor degradation further, we tested several potential nucleoside phosphorylase and thymidylate synthetase inhibitors at various concentrations. Our data show that the addition of 1 mM fluorouracil and 1 mM deoxyuridine to the culture medium largely prevents degradation of radioactive thymidine and iododeoxyuridine without unduly compromising the DNA-labeling efficiency of cells activated with mitogens or bacterial homogenates. Under these conditions, label incorporation increases linearly as the number of blast cells or the labeling time increases.