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The intimate, bidirectional link between neuroendocrine and immune systems is now accepted. A modulating effect of the nervous system on immune and inflammatory responses has been corroborated by identification of neuropeptide receptors on immunocompetent cells and the finding that neuropeptides can regulate leukocyte functions. The present study was undertaken to investigate the possible immunomodulatory role of sensory (SOM, CGRP and SP) and autonomic (VIP and NPY) neuropeptides in a murine model of cutaneous leishmaniasis, using two genetically different inbred mouse strains, BALB/c and C57BL/6, respectively susceptible and resistant to Leishmania (L.) major infection. The parameters studied were extent of splenocyte proliferation, as measured by thymidine uptake, and the ability of these cells to secrete IFN-gamma and IL-4 by using a two-site ELISA, upon in vitro challenge with L. major parasites and addition of the neuropeptides. The resistant mouse splenocyte proliferation was enhanced by SOM, CGRP, and VIP at 10(-5), 10(-6) and 10(-9) M concentration, respectively, but was inhibited by NPY at 10(-5) M. Proliferation of the splenocytes from the susceptible strain was inhibited by SOM (10(-11) M) and CGRP(10(-5) M). Somatostatin, at various concentrations, stimulated IFN-gamma secretion in both mouse strain splenocytes, and IL-4 production in the susceptible mouse. Calcitonin gene-related peptide enhanced IFN-gamma secretion in susceptible mouse splenocytes at 10(-6), 10(-7) and 10(-9) M, as did VIP at 10(-10) M and NPY at 10(-7) M. Vasoactive intestinal peptide also stimulated IL-4 production in BALB/c splenocytes at all concentrations used. Substance P had no effect on either cell proliferation or cytokine secretion in either of the two mouse strains. These findings indicate that the nervous system, represented by sensory and autonomic nerve terminals and their content of neuromediators, may be involved in the pathophysiology of cutaneous leishmaniasis.

The serotonin antagonists ketanserin and methiotepine were tested for a modulating effect on the proliferative response of human peripheral blood T lymphocytes to mercuric chloride. This response was inhibited by ketanserin at 8 x 10(-5) mol/l and by methiotepine at 8.0 x 10(-6) mol/l. There were no additive effects at these concentrations of antagonists and at 10(-5) mol/l of serotonin. Low concentrations of ketanserin eliminated the inhibiting effect of serotonin on mercuric chloride induced proliferation of T lymphocytes. It thus seems as if the inhibiting effect of serotonin on T lymphocytes is mediated by 5-HT1c or 5-HT2 receptors, while the mechanism for the intrinsic inhibiting effect of the antagonists at present is unknown.

Lymphocytes in blood samples taken from the thymic, brachiocephalic and internal jugular vein of children undergoing thoracic surgery were compared regarding their phenotypic markers and their proliferative response to mercuric chloride (HgCl2) and phytohemagglutinin (PHA). Of these two mitogens, PHA stimulated the DNA synthesis of the lymphocytes from the thymic vein to a significantly higher degree than those taken from the brachiocephalic or internal jugular vein. The response to HgCl2 resulted in the highest stimulation of the DNA synthesis in cells from the thymic and the brachiocephalic veins, though the differences were not significant. The higher reactivity to PHA and the tendency to higher reactivity to HgCl2 of lymphocytes taken from efferent thymic blood might be due to a higher frequency of T cells. This, however, could not be verified by immunohistochemical staining, as Leu4-positive cells occurred in the same proportion in all three venous samples. We therefore suggest that the passage through the thymus of circulating T cells may increase their immune reactivity by the influence of thymic maturation hormones.

The effect of unfractionated heparin and a low molecular weight heparin fragment was tested on the DNA synthesis response of human thymocytes to mercuric chloride. In a concentration of 0.01-0.11 mg/ml, unfractionated heparin somewhat stimulated this response, while the heparin fragment at 11.1 mg/ml gave an evident stimulation of the response and a lower stimulation degree at 1.1 mg/ml.

The metal allergens mercuric chloride and nickel sulfate were found to stimulate DNA synthesis of different in vitro cultured lymphoid cells from newborn guinea pigs. In contrast to earlier findings in adult animals (where spleen cells were most consistently stimulated), in newborn animals thymocytes were the most clearly stimulated lymphoid cells. When separating thymocytes by peanut agglutinin agglutination, both agglutinated and nonagglutinated cells were stimulated, indicating that both functionally immature and mature thymocytes are the target cells for this effect of metal allergens.

Mercuric chloride and, to a lower extent, nickel sulfate, stimulated DNA synthesis of both thymocytes and peripheral blood lymphocytes. The metal allergens stimulated both cell types at a lower degree than lectinic mitogens (PHA, Con A and PWM) did. In peripheral blood lymphocytes the stimulation degree was higher than in thymocytes after addition of metal allergens as well as lectinic mitogens. The presence of serum seemed to have a protective and potentiating role regarding the effect of mercuric chloride and lectinic mitogens, the effect of nickel sulfate being mainly unchanged. With increasing age of the individuals, an increase in the stimulation degree with mercuric chloride and lectinic mitogens was indicated, while nickel sulfate gave a decrease.

The effect of unfractionated heparin and a low molecular weight heparin fragment was tested on the DNA synthesis response of human peripheral blood T lymphocytes from nickel-allergic patients, activated by mercuric chloride and nickel sulfate. An inhibition was found with unfractionated heparin at a concentration of 1.1 mg/ml, when added at 1 h after mercuric chloride and nickel sulfate and with the same concentration of the heparin fragment, when added at 1 h after nickel sulfate, no effect was seen after addition at 72 h after the salts. Both heparin preparations in concentrations of 0.0001-0.11 mg/ml stimulated the response to nickel sulfate and in concentrations of 0.001-0.11 mg/ml stimulated the response to mercuric chloride. Thus the heparin preparations seem to have different modulating effects on both nickel and mercury activation of lymphocytes dependent on both heparin concentration and the point of time when it was added in the course of the activation process.

Neuropeptides and monoamines are found in tissues where immune reactions are initiated such as the skin, gut and respiratory tract. In these tissues they might influence lymphocyte activation in inflammatory diseases. Both stimulatory and inhibitory effects have been described. The inhibitory effects may prove to be of pathophysiological and pharmacological importance. Studies both in vitro and in vivo showing that various neuropeptides and monoamines may inhibit reactions such as T lymphocyte proliferation, Blymphocyte proliferation and antibody synthesis, lymphocyte migration and cytotoxicity, are reviewed.

Peripheral blood lymphocytes from nickel-allergic and control subjects were fractionated into different subpopulations on the basis of density on Percoll, in an attempt to improve the lymphocyte transformation test in diagnosis of nickel allergy. Significant differences were obtained between the subject groups with cells recovered at densities of 1.046 and 1.058 g/ml, however, a higher significant difference was found in unseparated cells. The results still support the relative value of the transformation test as a diagnostic tool in nickel allergy. In addition, an unspecific mitogenic effect of nickel on lymphocytes is emphasized.

The influence of beta-endorphin, somatostatin, substance P (SP) and vasoactive intestinal peptide (VIP) was tested on the proliferative response of peripheral blood T lymphocytes of nickel-allergic subjects to nickel sulfate. With somatostatin, 10(-6)-10(-10) M, SP, 10(-9) and VIP, 10(-7)-10(-8) M, added 1 h after nickel sulfate, there was an enhancement of the response, while a slight suppression was obtained with SP, 10(-6) M. At 3 days after nickel sulfate, beta-endorphin, 10(-6)-10(-12) M, somatostatin, 10(-7)-10(-9) M and SP, 10(-7)-10(-11) M, gave an enhancement of the response.

Metal allergen concentrations inhibiting lymphoid cell DNA synthesis were tested on short-time cultured nonadherent and nonseparated thymic and splenic cells. With all tested metal allergens, the DNA-synthesis-inhibiting effect was more marked for nonadherent compared to nonseparated splenic cells. In thymocytes, a stronger inhibition of nonadherent cells was seen after addition of mercuric chloride. A protective or modifying role of adherent cells towards inhibiting or toxic effects of metal allergens in vitro is postulated.

Neuropeptides and monoamines have been found in tissues where immune reactions are initiated such as the skin, gut, and respiratory tract, and in these tissues neuropeptides and monoamines might be involved in the regulation of lymphocyte activation. Studies both in in vitro and in vivo showing that various neuropeptides and monoamines may influence reactions such as T lymphocyte proliferation, B lymphocyte proliferation, and antibody synthesis, lymphocyte migration, and cytotoxicity will be reviewed.

A factor an ultrafiltrated (UM 10) extracts of calf thymus, liver and spleen stimulated the uptake of 3H-thymidine in DNA of cultured lymphocytes. The factor was purified by ion-exchange chromatography and gel chromatography and identified as alanine, which is lacking in the culture medium, RPMI 1640. An optimal amount of L-alanine increased the uptake of 3H-thymidine in DNA of lymphocytes from different species by about 100%. L-alanine should be regarded as a growth factor for lymphocytes in vitro and should be added to RPMI 1640, when this tissue culture medium is used for lymphocytes.

Different lymphocyte separation procedures, Percoll and Ficoll-Paque density sedimentation and gravity sedimentation, were tested in order to get optimal results in the lymphocyte transformation test in diagnosis of nickel allergy. Percoll at both investigated times, 3 and 6 days, gave the highest lymphocyte DNA synthesis response to nickel sulfate in nickel-allergic subjects and the most significant difference against control subjects. With all tested separation procedures there was an overlap between the patient and control group as regards the individual responses.

Sodium lauryl sulfate, a model substance in testing skin irritability was examined with regard to its effects on DNA synthesis and fine structure of human thymocytes incubated in vitro. At 5 h, incorporation of 3H-thymidine into DNA was inhibited with a discernable effect at 3 X 10(-4) M in serum-free medium and at 6 X 10(-4) M in medium to containing 15% serum. Under the former conditions, the effect on DNA synthesis was accompanied by disintegration of the cells as observed electron-microscopically. In contrast, no clear effects on cell morphology were seen in the latter case, in spite of a strongly depressed replicative activity. After 48 h of culture in medium containing 15% serum, there was a marked decrease in cell number due to spontaneous cell death and, consequently, a low rate of DNA synthesis. Sodium lauryl sulfate suppressed the incorporation of 3H-thymidine into DNA at 1.2 X 10(-3) M. No clear alterations in cell morphology were observed at 3 X 10(-4) M, whereas signs of irreversible cell damage, including pyknotic nuclei, were seen at 6 X 10(-4) M and complete disruption of most cells occurred at 1.2 X 10(-3) M. The results show that sodium lauryl sulfate inhibits DNA synthesis in human thymocytes and that there is a partial discrepancy between this inhibition and the adverse effects on the structural organization of the cell. It is proposed that the irritant effect of sodium lauryl sulfate in vivo is due to the breaking up of lymphoid or other cells and a consequent release of material that gives rise to an inflammatory response.