Resistance to hydrocortisone conferred upon thymocytes by a thymic humoral factor

Stimulatory effect of N-(1-deoxy-beta-d-fructopyranos-1-yl)-l-proline on antibody production in mice

Synthesized N-(1-deoxy-beta-d-fructopyranos-1-yl)-l-proline (Fru-Pro), an Amadori rearrangement product, has been investigated for its immunomodulatory effects. We evaluated the effects of Fru-Pro on the in vivo and in vitro activity in the regulation of the mice immune response. Haemagglutination antibody titre, plaque forming cell assay, E-rosette forming assay and cytotoxic test were studied. It has been demonstrated that the compound shows immunostimulating properties. In conclusion, present investigation suggests that the Fru-Pro is biologically functional, improves the immune system and might be regarded as an immune response modulator.

The effect of a peat-based preparation on mitogen-induced proliferation of thymocytes in non-treated and hydrocortisone-suppressed mice

The studies were carried out on Balb/c mice (5-6 weeks of age) treated with a peat-based preparation (PBP), administered i.p. once or four times at 24 h intervals at doses of 0.01; 0.1 or 1 mg/kg. Additionally, hydrocortisone was injected i.p. to selected mice at a single dose of 125 mg/kg. The results show that PBP temporarily enhances the proliferative capability of murine thymocytes stimulated in vitro with concanavalin A (Con A) and phytohemagglutinin (PHA). The effect of PBP depends on the number of subsequent doses, but does not depend on the dose applied. A single PBP administration does not affect the proliferative response of thymocytes to Con A and PHA. A single injection of PBP (doses from 0.01 to 1 mg/kg) does not change the number of thymic cells and weight ratio of this organ. Increased doses of subsequent PBP injections (0.01 and 0.1 mg/kg) do not affect the number of thymocytes, but temporarily increase the weight ratio of the thymus two days after the last injection. Administration of PBP prior to hydrocortisone prevents the suppressive effect of the drug on proliferative response of thymocytes stimulated in vitro with Con A and PHA, at the same time increasing the proliferative response of thymic cells to the two mitogens in relation to the control group (hydrocortisone-free). The effect of a single dose of PBP depends on the dose applied--the weakest preventive effect was observed at a dose of 0.01 mg/kg. An increase in the number of subsequent PBP doses, irrespective of a dose applied, prolongs the protective action of the drug on proliferative activity of thymocytes stimulated in vitro with these mitogenes. Moreover, the results obtained in the studies show that PBP partially prevents the suppressive effect of hydrocortisone, as the number of thymic cells and weight ratio of this organ drastically decreased. PBP accelerates regeneration of the thymus, but this depends on a dose applied and the number of subsequent doses. The result was the strongest and the fastest when PBP was injected four times at a dose of 1 mg/kg. It seems quite likely that the thymic regeneration due to PBP is connected with the effect of this drug on maturation and differentiation of thymic cells.

The toxicity of seed extracts and their fractions from Lupinus angustifolius L. and Lupinus albus L

Seed extracts obtained from Lupinus albus and Lupinus angustifolius by treatment with 48% ethanol contained ca. 10% alkaloids (on a dry weight basis) and were non-toxic. Their acute toxicity (LD50) in the mouse is > 4000 mg kg-1 body wt. After fractionation, the extract from L. angustifolius seeds afforded several fractions with differing toxicities (LD50 750-4000 mg kg-1 body wt.). None of the fractions tested in vitro were toxic. The results obtained showed that, in spite of the alkaloids, other low-molecular-weight constituents present significantly modified the toxicity of the lupin extracts.

Physiological relationships among stress, viruses, and cancer in experimental animals

Anxiety-induced psychoneural stimulation, via the hypothalamic-pituitary axis, activates the adrenal cortex to release corticosteroids, which elicit various alterations of corticoid-sensitive cell-mediated immunologic processes. Stress sensitive murine tumor-host experimental models have been utilized to demonstrate various effects of stress upon aspects of tumor development. Although many of the observed anxiety-induced alterations of tumor-related parameters can be interpreted in terms of corticoid-induced modifications of immune functions, other observations are more difficult to interpret, and may be caused in part by corticosteroid-independent modulation of lymphocyte functions. In the case of tumors induced by oncogenic viruses, anxiety-induced plasma corticoid elevations may also act independently of the immune system to stimulate tumor development via hormone binding sites on proviral DNA. Rigorously controlled environmental and experimental conditions are fundamental for the demonstration and interpretation of stress-related phenomena. Technical prerequisites include protective animal facilities, special handling procedures, the use of nontraumatic stressors, and the recognition of vital psychosocial, coping and timing factors. Various biologic factors, such as sex, genetic substrain differences and common interfering viral infections, must also be controlled or taken into consideration.

Development of three Thy 1 + cell populations induced by distinct thymic stromal elements

Thymectomized, X-irradiated mice, reconstituted with T cell-deprived bone marrow, were treated for 10 weeks with various thymic stromal fractions. Their splenocytes were then assayed for Thy 1 antigen. Three Thy 1 + populations were identified: cells of population 1 were found in mice treated with a membrane extract of thymic stroma. They had a high Thy 1 concentration which could be reduced (Population 2) after incubation with a thymic hormone preparation (STF). Population 3 was also composed of high Thy 1 cells but these were induced by STF treatment in vivo and could not be further differentiated into low Thy 1 cells.

Regluating factors in helper T-cell maturation

The effect of soluble and insoluble thymic fractions (STF and ITF, respectively) on the antibody response to sheep red blood cells (SRBC) was tested at different times after injection in mice. In normal mice, a temporary increase in the number of plaque forming cells (PFCs) was observed after injecting either ITF and STF, this increase being more prolonged when both fractions were injected together. In thymectomized, lethally irradiated mice repopulated with syngeneic untreated bone marrow, full reconstitution of T helper function was achieved only if both ITF and SFT were injected, partial reconstitution being obtained when either of these fractions was administered alone. In thymectomized, lethally irradiated mice repopulated with T-depleted bone marrow, reconstitution of the T helper function was only achieved when both ITF and SFT were administered. These results show that ITF and STF together constitute all the essential elements of the thymic microenvironment necessary to support the entire differentiation process of prethymic precurosors into helper T cells.

Effect of a human serum thymic factor on hydrocortisone-treated thymocytes

A human serum thymic factors (SF) stimulated cyclic adenosine-3' ,5'-monophosphate (cAMP) synthesis in normal mouse thymocytes. Such stimulation was no longer observed when thymocytes were depleted of hydrocortisone (HC)-sensitive cells. It was concluded that SF selectively stimulate cAMP in HC-sensitive cells. Furthermore, incubation of thymocytes with SF enlarged the population of HC-resistant thymocytes. These results suggest that SF might act on HC-sensitive thymocytes increasing their cellular cAMP level and inducing their transformation in HC-resistant cells.

Cortisone sensitive T-cells in Peyers' patches

Pretreatment of donor lymphoid cells with cortisone has been shown to depress the T-cell subpopulation responsible for cellular proliferation in the GVH reaction. A quantitative assay as well as the histological criteria of the GVH reaction have been used in this study to demonstrate the presence of cortisone-sensitive T-cells within the Peyer's patches as well as in the spleen and mesenteric lymph nodes in the rat.

Increased reactivity of responding cells in the mixed lymphocyte reaction by a thymic humoral factor

A thymic humoral factor (THF) induces competence in a certain sector of the lymphoid cell population. The target cell for THF activity was studied using the one-way mixed lymphocyte culture (MLC). Cells from various lymphoid tissues (responding cells) were preincubated in THF for 1 hour and then mixed with mitomycin-C-treated cells (stimulating cells). The results obtained indicate that THF increases MLC competence of lymphocytes from spleen and thymus origin of intact mice and that of spleen of thymus-deprived mice. In contrast, no enhancing effect in the MLC response by THF could be observed when bone marrow-derived spleen cells, cortisone-resistant thymocytes or lymph node cells were used as responding cells. These results confirm our hypothesis that THF leads to differentiation of young thymus-derived (T) cells, promoting them to maturation and thus to the acquisition of full immune competence.