The effect of dietary zinc and prothymosin alpha on cellular immune responses of RF/J mice

Mice of the RF/J strain on a normal diet are defective in some aspects of cellular immunity, as evidenced by their susceptibility to infection with Candida albicans, their failure to release detectable quantities of circulating migration inhibitory factor (MIF) in vivo, and the presence of a low rate of phagocytosis and killing by peritoneal macrophages. When the mice were fed a high-zinc diet (300 ppm) for 4 weeks and then treated daily with 160 ng prothymosin alpha, an increase occurred in resistance to infection with C. albicans, in the capacity to release MIF in vivo into the circulation and in the capacity of peritoneal macrophages to engulf (phagocytose) and kill cells of C. krusei. In addition, the number of spleen lymphocytes producing antibody to a T-dependent antigen was significantly increased in the mice fed a high-zinc diet and inoculated daily with prothymosin alpha.

Evidence for thymus involvement in development of adrenal and gonadal endocrine functions in mice

The endocrine function of the gonads and adrenals was studied in mice with congenital athymia (mutation nude); in normal mice thymectomized at 3 days of age and in congenitally athymic mice with thymic transplants from the 5th day of life. The data demonstrated that abnormal function of the adrenals and testes in nude mice is related to the absence of a functionally active thymus during early ontogenesis. The effect of thymosin (fraction 5) on the formation of adrenal functional activity was studied in congenitally athymic and normal mice. Treatment with thymosin during the first days of life resulted in suppressed adrenal function in adult athymic and normal mice. When given to adult normal mice, thymosin also decreased adrenal function. It is suggested that the thymus and its hormone thymosine are of importance in the formation of endocrine functions during the postnatal period in mice.

Enhanced frequency of mitogen-responsive T cell precursors in old mice injected with thymosin alpha 1

Injection of old mice with thymosin alpha 1, a synthetic peptide consisting of 28 amino acid residues and exhibiting thymic hormone-like activity, increases the splenic frequency of T cell precursors. Young (3-month-old) or old (19-20-month-old) mice received a single i.p. injection of thymosin alpha 1 or of an equimolar amount of the N14 (N-terminal amino acid residues 1-14) or C14 (C-terminal amino acid residues 15-28) synthetic fragment of the thymosin alpha 1 molecule and their spleen cells were assayed 3 days later under limiting dilution conditions to assess the frequency of mitogen-responsive and interleukin 2-producing T cells. Injection of thymosin alpha 1 or of its N14 fragment increases the frequency of responsive T lymphocytes in old, but not in young mice whereas injection of the C14 fragment has no demonstrable effect in either young or old mice. These data are consistent with our previous observation that the biological activity of thymosin alpha 1 is restricted to the N-terminal half of the molecule and suggest that this peptide amplifies the pool of mitogen-responsive and interleukin 2-producing T cells in immunodeficient old mice.

Quantitative analysis of mitogen-stimulated cellular proliferation: effect of concanavalin A and thymosin interaction

Studies of mitogen stimulated lymphocyte proliferation have shown that considerable variation exists in the magnitude of response to specific mitogens. No standard method has been devised which would permit comparisons of the non-linear proliferation response between groups. In this study a mathematical correlation between mitogen stimulation and cellular response is defined using concanavalin A as the mitogen. A logistic equation was derived by least sum of squares regression analysis. The dose response relationship of concanavalin A stimulated peripheral blood mononuclear cell proliferation was natural logarithmic. A computing program was designed to accomodate any calculation related to proliferation assays. The efficacy of this program and the adequacy of the equation were confirmed after they were tested in thymosin fraction 5 treated cellular proliferation experiments. This study demonstrates a quantitative method for the comparisons of immunological proliferation response among groups.

Immunoregulatory effects of fraction 5 thymus peptides. I. Thymosin alpha 1 enhances while thymosin beta 4 suppresses the human autologous and allogeneic mixed lymphocyte reaction

Thymosin alpha 1 and thymosin beta 4, two peptides isolated from preparations of calf thymus fraction 5, were tested in the human mixed lymphocyte reaction (MLR). Thymosin alpha 1 was found capable of enhancing both the allogeneic and autologous MLR. On the contrary, thymosin beta 4 suppressed MLR proliferative responses. Study of the responses of the T cell subpopulations revealed that T4+ (helper/inducer) cells but not T8+ (suppressor/cytotoxic) are responsible for the enhanced, proliferative response to allo- and autoantigens in the presence of thymosin alpha 1. Both the autologous and the allogeneic proliferative responses of either T4+ cells or T8+ cells were not influenced by the addition of thymosin beta 4 in the cultures. However, when T4+ and T8+ subsets were cocultured, thymosin beta 4 was capable of activating T8+ cells to suppress the allogeneic and the autologous proliferative response of T4+ cells. These studies show that thymosin fraction 5 peptides exert immunoregulatory effects on the human MLR proliferative responses in vitro.

Thymosin-alpha 1 increases the capability to produce interleukin-3 but not interleukin-2 in nu/nu mice

Thymosin-alpha 1 increased the capability of nu/nu mice to produce interleukin (IL)-3 but not IL-2 when administered intraperitoneally at doses of 0.5 and 5.0 micrograms/kg twice a week for 3-6 weeks. Thy-1-positive cells were responsible for the production of IL-3, which was determined by proliferation of the IL-3-dependent cell line (FDC-P2) as well as by augmentation of the in vitro growth of hematopoietic stem cells (colony-forming unit S [CFU-S]). The IL-3 activity released by nu/nu splenocytes emerged in fractions coincidentally with IL-3 released by WEHI-3 cells on Mono Q anion-exchange chromatography. However, IL-2 activity determined by proliferation of the IL-2-dependent cell line was not detected in any fractions of the same chromatography. These findings indicate that IL-2 is not always coproduced with IL-3 by Thy-1-positive cells. This suggests, taken together with results from previous studies about the cells producing IL-2 and IL-3 by other investigators, that thymosin-alpha 1 exerts its effect at an early stage of T cell differentiation to induce a T cell subpopulation capable of producing IL-3 (but not yet IL-2). Based on the present findings, we discuss the mechanism of action by which thymosin-alpha 1 exerts its diverse effects in immunosuppressed hosts but not a potentiating effect in healthy normal animals or in in vitro assays of T cell function.

Corticosterone-releasing activity of immune mediators

Products derived from the activated immune system have been reported to modulate neuroendocrine function. In addition, a direct connection between neuroendocrine and immune responses to stress has recently been proposed. We now provide evidence that heterogeneous lymphokine-containing supernatants from mitogen-stimulated rat spleen cells can stimulate both basal and corticotropin-induced corticosterone secretion from rat adrenal cells in an in vitro perifusion system. Moreover, thymosin alpha 1, a 28-amino acid residue peptide found both in thymus and lymphocyte-derived supernatants was also able to synergistically stimulate corticotropin-stimulated corticosterone release, without affecting basal corticosterone output in this same in vitro adrenal cell perifusion system. These results reinforce the suggestion about the existence of bidirectional interactions between the immune and neuroendocrine systems. They also indicate that this communication may occur directly at the adrenal gland level, a major effector site of the body's response to stress.

Immature circulating lymphocytes in severely malnourished Guatemalan children

The percentage of peripheral blood lymphocytes forming rosettes with sheep erythrocytes (E-rosettes) was determined in 33 severely malnourished Guatemalan children, and in two groups of clinically well but mildly growth retarded children from the same environment. Mean E-rosettes in the acutely ill patients was lower than the value observed in the mildly malnourished children, although there was considerable overlap between groups. These data differ from previously published studies of severely malnourished children from other parts of the world in that not all patients had decreased values for E-rosettes, in contrast to the uniform depression reported by others. As all patients were clinically similar, the results suggest that there may be specific nutrient defects associated with protein-energy malnutrition that particularly affect immune function. In addition, in vitro incubation of lymphocytes from the acutely malnourished children with the thymic factor, thymosin fraction 5, increased the percentage of E-rosettes in a dose-dependent fashion. These data suggest that immature, thymosin-responsive T cells are present in circulation. It is possible that in vivo thymosin administration may be beneficial for malnourished individuals.

[Role of helper T-lymphocytes in modulating the humoral immune response to cholera enterotoxin]

The role of helper T-lymphocytes in the modulation of humoral immune response to sheep red blood cells with choleragen has been studied in vivo, the populations of cooperating marrow cells, formed in mice under the action of hydrocortisone being used as a model. In adoptive transfer marrow cells, taken from mice on day 12 after thymectomy and from mice previously treated with antithymocyte serum, have proved incapable of humoral immune response. Choleragen, similarly to theophylline, normalizes the humoral immune response of marrow cells in thymectomized mice, but inhibits this response in intact ones, while thymosin fraction 2 restores it again, thus abolishing the action of choleragen and theophylline. The opposite effects rendered by choleragen and theophylline on humoral immune response, depending on the hormonal status of the animals and the possibility of influencing these effects by means of thymosin fraction 2 indicate that the population of helper T-lymphocytes are selectively sensitive to changes in the concentration of intracellular cAMP. Their capacity for cooperative interaction in the immune process is regulated by thymic hormones and forms the basis of the mechanism permitting the modulation of humoral immune response with choleragen.

Effect of partial testosterone replacement or thymosin on anti-DNA in castrated (NZB X NZW)F1 males

Castration of young (3-week-old) but not older (3-month-old) male (NZB X NZW)F1 mice was associated with autoantibody production similar to that of untreated female littermates. The castration-induced disease provided a unique model for the evaluation of therapeutic modalities during the first 9 months of life. Castrated male (NZB X NZW)F1 mice were treated with either long-term thymosin (fraction 5) or testosterone for different periods of time. Continuous testosterone replacement abolished the autoimmune disease-accelerating effects of castration at 3 weeks. Brief treatment during either the early or the later periods of life of castrated (NZB X NZW)F1 males was insufficient to prevent accelerated anti-DNA production. Thymosin treatment, when started at the time of castration and continued through life, abolished the rise in anti-DNA. These studies suggest that androgens work throughout the first 7 months of life of the mouse to suppress anti-DNA and that lack of androgens for a relatively brief period allows anti-DNA production to be initiated. Once initiated it cannot be completely suppressed. The cellular basis of the fixed aspect of this process is unknown. A possible role of the thymus is suggested by the ability of thymosin to suppress anti-DNA.

The synthesis of peptides with potential thymic hormone activity: the synthesis of endo-Arg38a-deacetylthymosin beta 10

A tritetracontapeptide corresponding to the entire amino acid sequence of endo-Arg38a-deacetylthymosin beta 10 was synthesized by a conventional solution method. Seven peptide fragments were assembled, followed by deprotection with 1 M trifluoromethanesulfonic acid-thioanisole-Me2Se in trifluoroacetic acid. In preliminary experiments the synthetic tritetracontapeptide increased the entire peripheral T-cell population and a helper T-cell subset when incubated in vitro with blood which was obtained from a uremic patient with pneumonia, but a suppressor/cytotoxic T-cell subset was unaffected under these conditions. The synthetic endo-Arg38a-deacetylthymosin beta 10 was as active as synthetic deacetylthymosin beta 10 in this in vitro assay.

Reduction in responsiveness of thymocytes to phytohemagglutinin during bladder tumor induction and restorative effects of thymosin fraction 5 in rats

Urinary bladder tumors were induced in female Wistar rats by oral administration of N-butyl-N-(4-hydroxybutyl) nitrosamine [(BBN) CAS: 3817-11-6]. Hypertrophy or vascular formation was observed in the bladder membrane 8 weeks after BBN administration, and tumors became visible at the 15th week. At the 20th week, approximately 95% of these rats had bladder tumors. The response of thymus lymphocytes to phytohemagglutinin (PHA) in these BBN-treated rats began to decrease from the 10th week and decreased significantly from the 18th week as compared with that in untreated rats. This reduced response to PHA was slower in comparison with the reduced response to concanavalin A. When thymus lymphocytes were preincubated with thymosin fraction 5 in vitro, the response to PHA improved between the 8th week and the 20th week. Furthermore, when the thymus small lymphocyte population was separated into 3 subpopulations by discontinuous density gradient centrifugation and adhesion column, the restorative effect of the thymus hormonal product was greater in the intermediate and heavier subpopulations.

Thymosin fraction 5 stimulates the release of prolactin from cultured GH3 cells

Thymosin fraction 5, a bovine thymus preparation, has recently been implicated in the regulation of neuroendocrine function. The purpose of the present study was to investigate the effects of thymosin fraction 5 treatment upon the GH3 rat pituitary cell line. Thymosin fraction 5 stimulated prolactin (PRL) release from these cells in a dose and time dependent manner. These results suggest that a product of the endocrine thymus may regulate the release of PRL.

Prothymosin alpha restores the depressed autologous and allogeneic mixed lymphocyte responses in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by a variety of profound T-cell abnormalities among which are decreased autologous and allogeneic mixed lymphocyte reactions (auto-MLR and allo-MLR, respectively). In a group of 10 patients with SLE, the mean auto-MLR and allo-MLR responses, tested by tritiated thymidine incorporation, were significantly decreased. If optimal doses of highly purified prothymosin alpha (ProT alpha) were present during the auto- of allo-MLR, the T-cell proliferative responses of SLE patients were increased to normal levels. ProT alpha had more pronounced enhancing effect in patients than in normal individuals. Among patients, ProT alpha was more effective in those who had active disease and low proliferative responses. These results demonstrate that ProT alpha can fully restore the deficient T-cell proliferative responses in auto- and allo-MLR in patients with SLE. ProT alpha, or a certain peptidic fragment of it, could prove potentially useful in the treatment of SLE.

Effect of two thymosin fraction 5 polypeptides on human peripheral blood lymphocytes

Thymosin fraction 5 polypeptides beta 4 and alpha 1 were tested for their ability to affect certain immunological parameters of human peripheral blood lymphocytes (PBL). PBL were cultured with various concentrations of the peptides for 24 hours. Thymosin beta 4 was found to induce a significant decrease in the expression of the Fc alpha receptors of PBL, as well as in their ability to express antibody dependent cellular cytotoxic (ADCC) activity. In addition, this peptide had the ability to increase the percentage of T4 lymphocytes in normal and immunosuppressed donors and to decrease the percentage of T8 positive cells in normal donors. Finally, beta 4 peptide caused a small increase in the capacity of peripheral blood lymphocytes to form sheep red blood cell (SRBC) rosettes (ER). In parallel experiments thymosin alpha 1 was found inactive. The results presented here indicate that thymosin beta 4 may be used as an immunoregulatory molecule in patients with immunodeficiencies.

Thymosin fraction 5 stimulates secretion of immunoreactive beta-endorphin in mouse corticotropic tumor cells

In addition to reconstituting immune competence, the thymus gland preparation, thymosin fraction 5 (TSN-5), has recently been shown to stimulate secretion of hormones from the hypothalamic-pituitary adrenal axis in vivo and from pituitary corticotropes in vitro. The purpose of the present study was to investigate the effects of TSN-5 on secretion of immunoreactive beta-endorphin (i beta-E) by mouse corticotropic tumor cells. The release of i beta-E by AtT-20 pituitary tumor cells was increased in a dose-dependent manner by concentrations of 30-600 micrograms/ml of TSN-5, whereas concentrations greater than 1,000 micrograms/ml were increasingly less effective in stimulating secretion. TSN-5 (600 micrograms/ml) significantly stimulated i beta-E release within 7 min; maximal secretory responses (up to 275% of control release) occurred by 4 hr. The secretory response of AtT-20 cells to 600 micrograms/ml TSN-5 (37.9 +/- 2.0 vs. 16.1 +/- 1.0 ng i beta-E/ml/4 hr, mean +/- SE) was similar in magnitude to release evoked by 0.1 microM corticotropin-releasing factor (CRF). Combining TSN-5 and CRF treatments increased secretion of i beta-E to nearly 600% of control levels, an effect greater than an additive influence of the two independent treatments. Whereas CRF treatment reduced the levels of i beta-E in AtT-20 cell extracts after 24-hr treatment by 45% (231.8 +/- 24.7 vs. 417.2 +/- 17.8 ng i beta-E/mg protein, CRF vs. vehicle treatments, respectively), TSN-5 did not significantly alter cellular hormone content. Neither TSN-alpha 1 nor TSN-beta 4, two of the component peptides of TSN-5, affected basal or CRF-stimulated release of i beta-E, indicating that an unidentified constituent(s) is corticotropic.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppressive effect of thymosin fraction 5 on proliferation of cultured human T lymphocytes

The effects of thymosin fraction 5 (F5), an extract of bovine thymus containing multiple polypeptides, on the proliferation of cultured T cells (CTC), a continuously proliferating subpopulation of peripheral blood T lymphocytes, stimulated by either phytohemagglutinin (PHA) or delectinated interleukin 2 (IL-2) were studied. Addition of F5 to cultures significantly and consistently inhibited CTC responsiveness to PHA, with the degree of inhibition being greater using a suboptimal concentration of mitogen. F5 did not significantly or consistently inhibit CTC proliferation induced by IL-2. These studies suggest that the suppressive effect of F5 may be primarily mediated by decreased IL-2 production instead of effects on IL-2 activity or efficiency in stimulating CTC proliferation. Since prostaglandins inhibit the proliferation of CTC in response to PHA or IL-2 (R.D. Maca (1983) Immunopharmacology 6:267), studies were undertaken to determine if the observed inhibition was mediated by effects of F5 on prostaglandin E2 (PGE2). The inhibitory effect of F5 on PHA responsiveness of CTC was not affected by the addition of indomethacin indicating that suppression by F5 is not mediated by stimulating the production or release of cyclooxygenase-derived prostaglandins, such as PGE2. Furthermore, PGE2 could not be detected in supernatants of F5-treated CTC stimulated by PHA. When PGE2 was added to F5-treated CTC cultures, the PHA response was inhibited indicating that the suppressive effects of F5 and PGE2 were additive and that F5 did not modulate the sensitivity of CTC to PGE2.(ABSTRACT TRUNCATED AT 250 WORDS)

Solid phase synthesis of thymosin beta 9

Thymosin beta 9, a 41 residue thymic polypeptide, has been synthesized by a solid phase method. A modification of the low HF method was used to deprotect and cleave the peptide from the resin. Thymosin beta 9 was then obtained in analytically pure form by a one-step purification procedure in 32% yield. The activity of thymosin beta 9 in the terminal deoxynucleotidyl transferase assay was greater than calf thymus fraction 5, but comparable to thymosin beta 4. In contrast to thymosin alpha 1, neither beta 4 nor beta 9 was active in the rosette inhibition assay.

Suppression of cellular immunity by head and neck irradiation. Precipitating factors and reparative mechanisms in an experimental model

A model was developed in C3H mice to investigate the immunosuppressive effects of head and neck irradiation and to explore mechanisms for repair of the defects. Mice receiving 1200 rad (12 Gy) of head and neck irradiation showed significant depression of delayed-type hypersensitivity, peripheral blood lymphocyte counts, spleen cell counts, and spleen cell production of interleukin-2. Treatment with optimal dosages of thymosin alpha 1 (T alpha-1) produced significant increases in all of these values, in some instances to levels higher than in the nonirradiated controls. In identical experiments with mice irradiated to a portal limited to the pelvic region, T alpha-1 induced only partial remission of the abnormalities. The dose response of T alpha-1 with head and neck irradiation showed a relatively limited dose range for immune restoration, a finding that warrants similar determinations in clinical trials with immunomodulating agents. The results suggest a potential clinical usefulness of T alpha-1 and also interleukin-2 in restoring cellular immunity after irradiation for head and neck cancers. The model appears to be useful for investigating immunomodulating agents before they are clinically evaluated as adjuvants with head and neck irradiation regimens.

Human prothymosin alpha: amino acid sequence and immunologic properties

Prothymosin alpha has been purified from human thymus and its amino acid sequence determined, except for a 15 amino acid segment including 10 glutamyl residues near the middle of the molecule. Like prothymosin alpha from rat thymus [A. A. Haritos, R. Blacher, S. Stein, J. Caldarella, and B. L. Horecker (1985) Proc. Natl. Acad. Sci. USA 82, 343-346], human prothymosin contains the thymosin alpha 1 sequence at its NH2-terminus. It contains a total of 109-110 residues compared to 111-112 for rat prothymosin alpha, with deletions corresponding to positions Gln39 and Lys108 of the rat polypeptide. Human prothymosin alpha also differs from rat prothymosin alpha at positions corresponding to residues 87, 92, and 102 of the latter, with substitutions of alanine for proline, alanine for valine, and aspartic acid for glutamic acid, respectively. Human prothymosin is significantly less active than rat prothymosin in protecting mice against infection with Candida albicans and in stimulating release in vivo of migration inhibitory factor. Thus, the differences in amino acid sequences, present mainly the COOH-terminal half of the polypeptides, may determine species specificity in biological properties.

Neuroendocrine regulation of thymus hormones: hypothalamic dependence of "facteur thymique serique" level

The influence of the hypothalamus extract (HE) on the blood level of the "facteur thymique serique" (FTS) was studied. Hypothalami collected from young mice were pooled, homogenated in saline, and centrifuged; finally, the supernatant injected in old or thymectomized mice with no detectable levels of FTS. In the old mice the treatment results in a reappearance of this circulating thymic hormone; in contrast, in adult thymectomized animals, the HE injection was not able to induce FTS activity. When HE donors were pretreated with thymosin fraction 3, known to contain FTS among other active peptides, the capacity of such a hypothalamus preparation to induce reappearance of FTS in old animals is greatly diminished. The data presented here suggest that the capacity of the thymus to secrete FTS depends on a hypothalamic factor, and therefore the absence of this thymic hormone in the aged reflects a failure of the thymus linked to its impaired neurologic control. On the other hand it seems evident that a feedback system operates in order to regulate the release of this hypothalamus stimulatory factor.

In vitro effect of thymosin alpha 1 on the expression of peanut agglutinin binding by murine thymocytes

Thymosin alpha 1 induces the loss of PNA binding ability by subpopulation of thymic cells. This loss is probably due to an endocytic process. Nevertheless this disappearance is not a permanent one, suggesting a recycling of the PNA binding molecule. The cells that modulate their PNA binding sites after exposure to Thymosin alpha 1 are a small proportion of the total PNA+ thymocytes, indicating that not all thymocytes are susceptible to the thymic hormone Thymosin alpha 1. Conversely the exposure of thymocytes to Thymosin alpha 1 induces the disappearance of the binding sites for this ligand without further recycling, behavior expected for the receptor of a regulatory ligand. These results also indicate that the Thymosin alpha 1 and the PNA binding sites are on different molecules on the surface of the PNA+ thymocytes.