Biomedical subjects
Publications and source records attributed to L Hammarström.
Vitality of the periodontal ligament (PDL) is necessary for a successful healing after replantation of exarticulated teeth. In the present investigation newly extracted teeth from monkeys were stored in saline, milk or saliva for 1-3 h. Freeze sections were made and the vitality of the PDL was determined histochemically. Milk seemed to provide better storage conditions than saliva or saline.
The morphology of supragingival and subgingival calculus on extracted teeth was studied with the scanning electron microscope. Oral, crevicular, and fracture surfaces were examined. Both subgingival and supragingival calculus had a heterogenous core covered by a soft, loose layer of microorganisms. On supragingival calculus this layer was dominated by filamentous microorganisms while subgingival calculus was covered by a mixture of cocci, rods and filaments. The supragingival covering of filaments was oriented with the filaments approximately perpendicular to and in direct contact with the underlying dense calculus. This arrangement was rarely seen subgingivally where there was no distinct pattern of orientation. Some of the specimens of sub- and supragingival calculus were treated with sodium-hypochlorite. These lost the soft covering, and channels the same size as the filamentous organisms were found penetrating into the calculus. They were oriented prependicular to the surface in supragingival calculus but had no specific direction in subgingival calculus. The appearance of the channels supports the concept that calcification starts between the microorganisms in both subgingival and supragingival calculus.
Human chorionic gonadotropin (HCG) has previously been considered to be immunosuppressive and, thus, by prohibiting maternal rejection of the fetal transplant, to be one of the factors responsible for the successful outcome of pregnancy. The mechanism by which HCG exerts its pregnancy retaining effect is, however, as yet unknown. The present study shows that HCG has the capacity in mice of inducing lymphocytes which are subsequently competent to depress a polyclonal antibody response induced by different B cell mitogens. It is therefore suggested that HCG may exert its feto-protective action by inducing suppressor T cells. These lymphocytes would thus prevent the activation of cells which are responsible for transplant rejection.
With a modification of the protein-A plaque assay, cells secreting a given idiotype could be detected. Different anti-idiotypic antisera raised against the M-component of macroglobulinemia Waldenström patients were used. The antibodies did not cross-react with cell clones of other patients or normal controls. Spontaneous plaques, without prior cultivation, were mainly shown to be of IgM class, the majority being idiotype specific, in blood and bone marrow lymphocytes from these patients. This is in contrast to the predominance of Ig or IgA found in normal blood donors. A low but recognizable stimulation of the malignant clone may be observed when cells were stimulated by certain polyclonal B cell activators.
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In a complement-dependent assay, using protein A-coupled erythrocytes as target cells and anti-albumin immunoglobulin (Ig) as a developing serum, it was possible to detect single albumin-secreting hepatocytes as plaque-forming cells. Plasmacytoma cells were detected using anti-Ig antibodies and did not form plaques with anti-albumin Ig. This method can potentially be used for detecting any cell-secreting products in sufficient amounts.
Various purified cell wall lipopolysaccharides (LPS) from gram-negative bacteria and derivatives of these LPS were tested for their stimulatory capacity for human peripheral blood cells. Immunoglobulin (Ig) production was tested by an indirect plaque-forming cell assay using Staphylococcus aureus protein A-coupled erythrocytes and specific anti-Ig as developing serum. This method allows the detection of the majority of cells secreting Ig of a single class, and the number of plaque-forming cells detected are approximately 100-1000 times the amount obtained using normal sheep red cells as targets. LPS containing the O antigen-specific chain, as well as mutant products only containing lipid A and ketodeoxyoctonate trisaccharide, could induce cell division and antibody synthesis. The polypeptide antibiotic polymyxin B was found to inhibit LPS-induced activation. Furthermore, purified lipid A, complexed with bovine serum albumin, was also found to activate human peripheral blood B cells. These findings demonstrate that human peripheral blood lymphocytes can be activated by LPS and also indicate that lipid A is the active part of these molecules.
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Concanavalin A induced polyclonal antibody synthesis in normal spleen cells in vitro. Optimal responses were obtained by Con A concentrations lower than those optimal for induction of DNA synthesis. T cells, but not macrophages, were necessary for the effect. Spleen cells from nude mice were not activated, whereas cells from the LPS non-responder stain C3H/HeJ were activated to polyclonal antibody synthesis by Con A. Supernatants from Con A activated spleen cells could by themselves induce polyclonal antibody synthesis in untreated spleen cell cultures, even when Con A had been removed by absorption with Sephadex G-50 and when alpha-methyl-mannoside was present in the secondary cultures. T cells produced the active supernatants, which were competent to induce polyclonal antibody synthesis, but not DNA synthesis, in both H-2-incompatible and compatible strains. When the supernants were absorbed with erythrocyte antigens, they specifically induced an enhanced response, in secondary cultures, to the antigen used for absorption. Possible mechanisms of this specific effect are discussed.
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The effect of autologous normal mouse serum on activating properties of the polyclonal B cell activators lipopolysaccharide and purified protein derivative was studied. 'Low' concentrations (0.1-1%) were found to be slightly stimulatory, whereas 'high' concentrations (greater than 10%) were clearly inhibitory both for the induction of plaque-forming cells and for the DNA synthetic response. Similar effects were recorded in unstimulated cultures. Absorption of normal mouse serum with the erythrocytes used as target cells in the plaque assay resulted in less suppression or sometimes even in enhanced responses.
Human chorionic gonadotrophin (HCG) and human chorionic somatomammotrophin (HCS) were shown to suppress the proliferative T and B cell response induced by different mitogens in human and mouse lymphocytes. Thyroid stimulating hormone (TSH), sharing the alpha-chain subunit with HCG was devoid of effect suggesting that the immunosuppressive entity is localized within the beta-chain subunit. Human growth hormone (HGH) which is partly biologically cross-reactive with HCS did not impair mitogen responsiveness. HCG was also able to inhibit the differentiation of cells since the induction of antibody-formation was depressed. Expression of plaque forming cells was also reduced by addition of HCG directly in the PFC assay possibly reflecting the anti-complementary effect of this hormone, since cell mediated lysis of target cells by Con A activated lymphocytes, which is not complement-dependent, was unaffected by adding HCG in the assay system.
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Using the protein A plaque assay, the number of human cells secreting immunoglobulin of various classes after pokeweed mitogen stimulation was determined. At optimal response (on day 5-7) a mean of 58,354 IgM PFC/10(6), 34,207 IgG PFC/10(6) and 10,525 IgA PFC/10(6) cells was found when using peripheral blood lymphocytes. In spleen cells, peak values which were slightly higher than in blood, were obtained at day 4-6. The proportions of cells secreting light chains of either type were found to be comparable to those of unstimulated cells thus supporting the notion of the polyclonality of the response. Pokeweed mitogen stimulation of peripheral blood lymphocytes was found to be totally T-cell dependent whereas the response of spleen cells was not. When assayed for antigen-specific precursor cells in cultures stimulated by mitogen, the frequency of SRBC-specific IgM producing cells was found to be 1.3/1000 cells. This frequency was regularly found to be independent of medium supplement.
Activation of Na+, K+-ATPase has previously been suggested to be the triggering signal in mitogen-induced cell activation. Using a digitalis glycoside known to be a potent polyclonal B-cell activator, this hypothesis could be tested since digitalis activates ATPase at different concentrations in various species, depending on the degree of sensitivity to the toxic effects of glycosides. Lanatoside C was found to stimulate lymphocytes from glycoside resistant species such as rat, mouse and hamster. The possible involvement of Na+, K+-ATPase was made less likely by the similarity in dose--response profile in these cells although they have been reported to display varying degrees of glycoside resistance. Furthermore, using lymphocytes from digitalis-sensitive species such as man, guinea-pig or rabbit, no mitogenicity could be recorded, strongly suggesting a lack of correlation between glycoside-induced effects on Na+, K+-ATPase and cell activation.
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