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PubMed1979

The chemistry and biology of thymosin. I. Isolation, characterization, and biological activities of thymosin alpha1 and polypeptide beta1 from calf thymus.

A partially purified extract from thymus tissue termed thymosin Fraction 5 has been shown to reconstitute immunological deficiencies resulting from the lack of thymic function in several animal models, as well as humans with primary and secondary immunodeficiency diseases. Thymosin Fraction 5 consists of a family of polypeptides with molecular weights ranging from 1,000 to 15,000. Several of these polypeptides contribute individually to the biological activity of the parent compound. Two polypeptide components of thymosin Fraction 5, termed thymosin alpha1 and polypeptide beta1, have been characterized chemically and biologically. Thymosin alpha1 is a highly acidic molecule composed of 28 amino acid residues. This polypeptide has potent biological activity and has been found to be 10 to 1,000 times as active as thymosin Fraction 5 in one in vivo and several in vitro bioassay systems designed to measure differentiation and function of thymus-dependent lymphocytes (T cells). Polypeptide beta1, in contrast, is inactive in our bioassay systems, suggesting that it is not involved in thymic hormone action. Sequence analysis and homology studies have indicated that polypeptide beta1, although present in Fraction 5, does not contribute to the biological activity of thymosin Fraction 5.

Animals↗
PubMed1978

Thymosin in cancer patients: in vitro effects and correlations with clinical response to thymosin immunotherapy.

Studies on the effect of thymosin on T-cell levels in vitro among normal persons and cancer patients show that, in general, T-cell levels increase after incubation with thymosin in populations with low initial T-cell levels while the levels decrease in populations with high initial T-cell levels. In patients with small cell carcinoma of the lung receiving intensive chemotherapy also randomized to receive thymosin at a dose of 60 mg/m2, thymosin at a dose of 20 mg/m2, or placebo twice weekly, increased survival occurred in patients receiving the thymosin dose of 60 mg/m2. The increase in survival was greatest in patients with low pretreatment T-cell and alpha2HS-glycoprotein levels. These observations suggest that the cancer patients most likely to benefit therapeutically from adjuvant treatment with thymosin are those with relatively low initial T-cell levels and other parameters of cellular immunity.

Carcinoma, Small Cell↗
PubMed1979

The chemistry and biology of thymosin. II. Amino acid sequence analysis of thymosin alpha1 and polypeptide beta1.

The amino acid sequences of two polypeptide components of thymosin Fraction 5 termed thymosin alpha1 and polypeptide beta1 have been established. The sequences were determined by automatic Edman degradation of the intact molecules as well as by manual sequence analysis of the enzymatic cleavage products. Thymosin alpha1, an immunologically active polypeptide, is highly acidic with an isoelectric point of 4.2. This molecule is composed of 28 amino acid residues with acetylserine as the NH2 terminus. A chemically synthesized molecule of thymosin alpha1 has been found to be as active as the natural molecule in our bioassay systems. Polypeptide beta1 is a molecule consisting of 74 amino acid residues and has an isoelectric point of 6.7. This peptide is not biologically active in our assay systems, suggesting that it is not involved in thymic hormone action. The sequence of beta1 was found to be identical with ubiquitin and a portion of protein A24, a nuclear chromosomal protein. The relationships among these proteins are discussed.

Amino Acid Sequence↗
PubMed1979

Thymosin-induced suppression of proliferative response of human lymphocytes to mitogens.

The proliferative response of human peripheral blood lymphocytes to phytohemagglutinin, concanavalin A, and pokeweed mitogen were suppressed by thymosin. Greatest decreases were observed when cells were preincubated with thymosin for 18 h before a 3-d culture with mitogen in the presence of thymosin. However, significant suppression also occurred when lymphocytes were preincubated for 2 h and cultured with thymosin or preincubated for either 2 or 18 h and washed free of thymosin before culture. These effects were related to the concentration of thymosin and time of exposure to thymosin but not merely to a delay in the response to mitogen or to toxicity. The suppression of mitogen-induced proliferation by thymosin appeared to result from effects of thymosin on a suppressor cell because lymphocytes incubated with thymosin did not acquire increased responsiveness to mitogens as did cells incubated for 18 h in its absence and because mixing thymosin-pretreated lymphocytes with cells not preincubated with thymosin resulted in decreased responsiveness to photohemagglutinin.

Cell Division↗
PubMed2026

Thymosin-ɑ1 for people with chronic hepatitis B.

RATIONALE: Chronic hepatitis B is a global public health concern. It is caused by infection with the hepatitis B virus (HBV). The goal of treating chronic HBV infection is to prevent progression to chronic hepatitis, cirrhosis, hepatic decompensation, liver failure, hepatocellular carcinoma, and death. Individual studies have evaluated various immunomodulatory therapies with inconsistent results. Thymosin-ɑ1 is known to have antiviral effects; however, results of randomised clinical trials on the effects of thymosin-α1 as a potential treatment for people with chronic HBV have been inconsistent. OBJECTIVES: To assess the benefits and harms of thymosin-ɑ1 therapy in people with chronic hepatitis B. SEARCH METHODS: We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, four other databases and six trials registers, in addition to reference checking, citation searching, and contacting study authors to identify trials for inclusion. The latest search date was 10 June 2026. ELIGIBILITY CRITERIA: We included randomised controlled trials (RCTs) that evaluated thymosin-α1 at any dose, route of administration, or formulation type, in people with chronic hepatitis B regardless of age, sex, or ethnicity. Thymosin-α1 could have been administered as monotherapy, in combination with an additional drug, or in addition to standard medical treatment and compared with placebo, no intervention, the same additional drug, or the same standard medical treatment. OUTCOMES: Our critical outcomes were all-cause mortality, serious adverse events, and health-related quality of life. Among our important outcomes were HBV-related morbidity, HBV-related mortality, non-serious adverse events, and the proportion of people without histological improvements. RISK OF BIAS: We used the Cochrane Risk of bias 2 tool (RoB 2) to assess risk of bias. SYNTHESIS METHODS: We followed Cochrane methods. We conducted meta-analyses for predefined outcomes using data from the longest follow-up period, irrespective of the risk of bias judgements. We presented dichotomous outcome results as risk ratios (RRs) and continuous outcome results as mean differences, with 95% confidence intervals (CIs) at their longest follow-ups. We used the random-effects model for our primary analyses. We used GRADE to assess the certainty of the evidence for each outcome. INCLUDED STUDIES: We included 10 RCTs conducted in Bangladesh, China, Italy, Korea, Singapore, and Taiwan, with 1349 randomised participants (range: 12 to 690; 1045 (77.5%) were male). Among the trials reporting age, none included participants younger than 17 years (age range: 17 to 75 years). The trials were published between 1991 and 2018, and assessed thymosin-ɑ1 in adults with chronic hepatitis B infection, with or without comorbidities. Only two trials mentioned comorbidities (cirrhosis and acute-on-chronic liver failure). The trials compared thymosin-ɑ1, with or without a cointervention, with placebo or no intervention, or with the same cointervention. The control interventions were placebos in two trials and no intervention in two. The remaining six trials administered co-interventions, such as interferon, pegylated interferon, lamivudine, and standard medical therapy (entecavir or tenofovir), and entecavir. Follow-ups ranged from six months to five years after the end of treatment (median: 12 months). Four trials were funded by industry, five by research grants, and one provided no information. All 10 trials (11 records) provided data on at least one outcome in our review. We identified no ongoing trials. Sixteen studies are awaiting assessment due to incomplete reporting. We received no responses to our enquiries. SYNTHESIS OF RESULTS: Thymosin-ɑ1, compared with the control interventions, may reduce all-cause mortality (RR 0.53, 95% CI 0.29 to 0.96; I² = 0%; 3 studies, 907 participants; very low-certainty evidence), serious adverse events (RR 0.72, 95% CI 0.53 to 0.99; I² = 0%; 5 studies, 1056 participants; low-certainty evidence), HBV-related mortality (RR 0.53, 95% CI 0.29 to 0.96; I² = 0%; 3 studies, 907 participants; very low-certainty evidence), non-serious adverse events (RR 0.47, 95% CI 0.27 to 0.83; I² = 0%; 5 studies, 300 participants; very low-certainty evidence), and may have little to no effect on health-related quality of life (MD 0.70, 95% CI -2.55 to 3.95; I² not applicable; 1 study, 161 participants; very low-certainty evidence; score range: 0 to 100; the higher the score, the better) and on histological improvement (RR 0.51, 95% CI 0.13 to 2.06; I² = 74%; 2 studies, 702 participants; very low-certainty evidence). The evidence is very uncertain about the effect of thymosin-ɑ1 on hepatitis B-related morbidity (RR 0.86, 95% CI 0.54 to 1.40; I² = 3%; 3 studies, 854 participants; very low-certainty evidence). We judged the certainty of evidence to be low for serious adverse events and very low for the remaining outcomes. Reasons for downgrading were mainly due to study limitations, including overall high or some concerns for risk of bias; imprecision of the pooled effect estimates (including wide or very wide confidence intervals crossing the line of no effect, and small participant numbers); and inconsistency due to substantial heterogeneity (I² = 74%). The test for subgroup differences provided no evidence of differences in effect according to thymosin‑α1 administration for any outcome (P ≥ 0.05). AUTHORS' CONCLUSIONS: We assessed the certainty of evidence as very low for all outcomes except for serious adverse events (low). Therefore, we are not sure whether thymosin-α1 monotherapy versus placebo or no intervention, or with the same co-interventions, reduces all-cause mortality, serious adverse events, HBV-related mortality, and non-serious adverse events, nor whether it has any effect on quality of life (based on one trial) and histological improvement. The effect of thymosin-ɑ1 on HBV-related morbidity is very uncertain. We observed no statistically significant differences between trials with and without cointerventions. We found no ongoing trials. FUNDING: This Cochrane review had no dedicated funding. REGISTRATION: Protocol available via DOI: 10.1002/14651858.CD014610.

Humans↗
PubMed1979

Presence of thymosin-like factors in human thymic epithelium conditioned medium.

The objective of the present study was to determine whether or not thymosin and conditioned medium from human thymus epithelial cultures (HTECM) contain similar fractions, capable of inducing T-cell differentiation. Therefore we tested the ability of rabbit antisera to different thymosin fractions (thymosin fractions 5, 6 and alpha 1) of both bovine and human origin to block the stimulatory effect of HTECM on Con A and PHA response of mouse thymocytes. We also looked for reactivity of the antisera toward tissues of man, mouse and calf, and to tissue cultures of man and mouse. Anti-thymosin fraction 5 and 6, but not anti-thymosin-alpha 1, were found to inhibit the stimulatory effect of HTECM on both Con A and PHA responses. This cannot be attributed to cytostatic or cytotoxic effects of the antisera on thymocytes. No effect was seen when using antiserum to kidney fraction 5 or normal rabbit serum. In both tissue sections and tissue cultures of the different species tested, anti-thymosin reacts only with thymus epithelial cells. The reactivity is blocked by neutralizing the antisera with thymosin fraction 5 but not by kidney fraction 5. The reactivity is also strongly diminished by neutralizing the antisera with HTECM but not with supernatants of conditioned media from non-thymic tissues. The observations are highly suggestive for the presence of similar fractions in HTECM and thymosin, and that both are secreted by thymus epithelial cells.

Animals↗
PubMed1977

Thymosin reconstitution of T cell deficits in vitro in cancer patients.

Thymosin, a soluble extract of fetal calf thymus, has increased cellular immunity in children with thymic deficiency. Prior to therapy, an increase in thymus-dependent lymphocyte (T cell) levels in vitro after incubation with thymosin correlated with a rise in peripheral blood T cell levels and improvement in other parameters of cellular immunity. These correlations constituted the basis for a study of the effects of thymosin on T cell levels in vitro in cancer patients. Groups studied were 350 untreated patients with local-regional solid malignancies, 157 patients cured of these tumors, 340 patients studied at 523 intervals during radiation therapy, 80 patients receiving chemotherapy for disseminated solid malignancies, and 427 normal volunteers. Although there were significant differences among the groups in mean leukocyte, lymphocyte and T cell levels, among those with low T cell levels in each group there was a significant inverse relation between T cell levels after incubation with thymosin in vitro and initial T cell levels, with the exception of patients receiving chemotherapy. In patients receiving chemotherapy, T cell levels increased independently of initial T cell levels. These in vitro observations are consistent with evidence that a major effect of thymosin is maturation of T cell precursors; however, the effect is that of reconstitution at low T cell levels, and not of elevation to levels significantly above normal. The results provide a rationale for clinical trials with thymosin to maintain immune competence during radiation therapy and chemotherapy, and for a two-phase approach to immunotherapy of cancer utilizing thymosin for reconstitution of cellular defects followed by administration of agents that potentiate cellular immunity.

Adolescent↗
PubMed1978

Effect of altered lymphocyte function on immunologic disorders in NZB/NZW mice. III. Acceleration of disease by thymosin.

Administration of thymosin fraction V to NZB/NZW F1 mice, an animal model for human SLE, accelerated the appearance of proteinuria and anti-nDNA antibodies, increased deposition of immunoglobulins in kidneys, and significantly shortened survivals. Although the addition of thymosin to in vitro cultures of spleen and lymph node cells from thymosin-treated mice increased DNA synthesis in response to stimulation with Con A, in vivo treatment with thymosin did not affect the Con A response. There was no effect on in vitro responses to PHA or LPS, or on IgM antibody formation to SRBC (T cell dependent) or SSS III (T cell independent) immunizations. Antibodies to thymosin or contamination of our thymosin preparations with nucleic acids could not be demonstrated. The acceleration of autoimmune disease produced by thymosin treatment could not be explained by alteration of the T and B cell functions studied.

Animals↗
PubMed1976

In vitro and in vivo studies with thymosin in cancer patients.

Thymosin, fraction V, prepared by the method of Goldstein et al., was studied in in vitro lymphocyte cultures with cells obtained from normal subjects and patients with disseminated cancer. Thymosin lowered blastogenic activity in some patients, did not affect it in others, and increased counts in still others. There was a statistically significant depression in baseline (prethymosin) counts from both normals and patients when individuals whose counts increased in the presence of thymosin were compared with other subjects. We conclude that thymosin tended to raise depressed blastogenesis into the normal range without causing supranormal activity or without itself acting as a mitogen or antigen. Eighty-two in vivo courses in thymosin were given to 32 patients. Analysis of the first thymosin courses in these 32 patients shows that immunologic reconstitution occurred in patients with originally depressed T-cell function and numbers, whereas little change was apparent in patients with initially intact tests of T-cell activity. Clinical effects were equivocal; however, no systematic clinical trial was conducted. Toxicity was minimal (four of the 32 patients); in each case, it consisted of inflammation at the injection site. The in vitro and in vivo results of this study suggest that thymosin therapy modulates and partially normalizes T-lymphocyte numbers and function.

Humans↗
PubMed1977

Thymic-dependent anti-hapten response in congenitally athymic (nude) mice immunized with DNP-thymosin.

Immunization of congenitally athymic (nu/nu) and adult thymectomized, irradiated bone marrow, reconstituted (TxBm) mice with DNP5-thymosin (dinitrophenylated-bovine thymosin fraction 5) was found to elcit IgM and IgG anti-DNP plaque-forming cells in these animals. Further studies indicated that this response was antigen specific and not due to polyclonal activation. Since the hormonal properties of the thymosin were retained following linkage with hapten and DNP-thymosin was immunogenic in CBA/N and CBA/N female X DBA/2 male)F1 male mice, animals previously shown to have an X-linked inability to respond to thymus-independent antigens, it was concluded that DNP-thymosin functions both as a hormone and as a T-dependent antigen in eliciting an immune response in nu/nu and TxBm mice. Additional support for this conclusion was provided by the demonstration that DNP-thymosin could specifically prime for and elicit an anamnestic response in nu/nu mice. These results indicate that further investigation of the immune activities of DNP-thymosin may provide valuable insight in characterizing the maturation of helper T cells and their subsequent interaction with B cells.

Animals↗
PubMed1976

In vitro effect of thymosin on T-lymphocyte rosette formation in rheumatic diseases.

The in vitro effect of calf thymosin fraction 5 on T-rosette forming cells (E-RFC) was studied in Sjögren's syndrome (SS), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE). The baseline percent E-RFC in sixteen normal controls was67-2 +/- 6-9. E-RFC was significantly decreased in SLE (42-6 +/- 17-0, P less than 0-0001) and SS (51-8 +/- 16-9, P less than 0-002) but not in RA (59-7 +/- 14-1). Ten of twenty-five SS patients and two of eleven RA patients had less than 50% E-RFC, and all showed a significant increase after incubation with thymosin (+ 16-5 +/- 6-5%, P less than 0-0001, and + 11 +/- 4-9%, P less than 0-001, respectively). Eleven of sixteen SLE patients had less than 50% E-RFC. Their response to thymosin was less dramatic but still statistically significant (+ 5-3 +/- 6-0%, P = 0-03). There was no response to thymosin in control subjects or in patients with baseline E-RFC greater than 50%. No increase in E-RFC was seen after incubation with calf spleen fraction 5 or known stimulators of cyclic-AMP. Sera from four active SLE patients, as well as the supernatant obtained from overnight culture of the lymphocytes from one SLE patients, were able to block T-rosette formation by normal lymphocytes, even after exposure to thymosin. Two 'blocking' sera were fractionated by sucrose density gradient ultracentrifucation. In one, the blocking capacity was found to reside in the 19S region containing IgM. In the second, the blocking capacity was in the 7S region containing IgG. Four 'blocking' lupus sera were depleted of IgG or IgM by immunoabsorption with goat anti-human IgG or goat anti-human IgM sepharose 4B. The blocking ability in three sera was partially decreased by depletion of either IgG or IgM, and in a fourth, only by removing IgG. The percent of lymphocytes staining with fluorescein labelled goat anti-human immunoglobulin antisera was increased in SLE patients (35-9 +/- 20-2 vs 21-7 +/- 5-9 in controls, P = 0-02). After overnight culture, the percent of staining cells decreased to normal values. These results suggest that thymosin can stimulate the differentiation of T-lymphocytes in patients with SS, SLE, and RA when the baseline E-RFC is decreased. Furthermore, the decreased percent E-RFC in SLE is probably due to cell-bound anti-lymphocyte antibodies that block sheep erythrocyte receptors on the T-cell and, possibly, thymosin receptors on undifferentiated lymphocytes.

Adolescent↗
PubMed1979

Thymosin restoration of cellular immunity to Blastomyces dermatitidis in T-cell-depleted mice.

The immunopotentiating properties of thymosin in thymectomized, lethally irradiated, bone marrow-reconstituted mice (ThyXBM) were characterized, using footpad sensitivity to Blastomyces dermatitidis. Normal mice were shown to exhibit increasing delayed-type hypersensitivity responses to killed yeast cells of B. dermatitidis after injections of the organism on days 0 and 7, as measured by footpad swelling tests. The footpad response of normal thymosin-treated mice was similar to that of normal, non-thymosin-treated mice. ThyXBM mice were unable to elicit a footpad response when similarly injected and footpad tested with B. dermatitidis. Thymosin-treated ThyXBM mice responded to footpad testing at a level that was 62% greater than the response seen in non-thymosin-treated ThyXBM mice. This peak response occurred on day 12. The results indicated that thymosin was unable to enhance immune responses of normal intact mice but could restore immunocompetence in a T-cell-depleted host, as measured by footpad sensitivity to B. dermatitidis.

Animals↗
PubMed1979

Spleen regeneration in mice after gamma irradiation and administration of thymosin.

The effect of thymosin (thymic humoral factor isolated from calf thymus) on regeneration of the spleen in mice after whole-body gamma irradiation was studied. Thymosin, in varied dosages (0.1--2.0 mg/day) applied subcutaneously before and after radiation exposure, stimulated splenic regeneration as indicated by increased splenic weight, number of endogenous splenic colonies and 59Fe and 125IUdR incorporation into the spleen. A control extract of brain tissue (cerebrosin) isolated in the same way as thymosin was applied to mice to verify specificity of thymosin. After cerebrosin application, a mild increase also was observed. Whereas a near maximal effect of thymosin was reached at a dosage of 0.1 mg, a comparable response with cerebrosin required a dosage of 1.0 mg. These data suggest that administration of thymosin has both a specific and non-specific effect on splenic regeneration and proliferation of hematopoietic stem cells.

Animals↗
PubMed1979

Thymosin fraction V and intensive combination chemotherapy. Prolonging the survival of patients with small-cell lung cancer.

Patients with small-cell bronchogenic carcinoma who received intensive remission-induction chemotherapy randomly received either thymosin fraction V, 60 mg/sq m or 20 mg/sq m twice weekly, or no thymosin treatment during the initial six weeks of chemotherapy. Chemotherapy was then continued for two years. Thymosin administration did not increase the complete response rate. Patients receiving thymosin, 60 mg/sq m, had significantly prolonged survival times relative to the other treatment groups. This benefit was due to prolonged relapse-free survival in complete responders to treatment. The mechanism by which thymosin increased survival duration is unclear but may relate to restoration of immune deficits due to disease or treatment.

Antineoplastic Agents↗
PubMed1977

Effect of thymosin in vitro on T cell levels during radiation therapy: correlations with radiation portal and initial T cell levels.

The effect of thymosin in vitro on percent T cells was determined in 388 blood specimens from patients with head and neck, mediastinal, and pelvic malignancies during radiation therapy, in 94 untreated patients with these malignancies, and 277 normal adults. Changes in percent T cell levels after incubation of lymphocytes with thymosin did not correlate with tumor histology or cumulative radiation dose, but in all groups correlated with radiation portal and initial T cell levels. T cell levels increased by a similar increment in normals and in the untreated patients. During irradiation, the mean levels after incubation with thymosin did not change in patients with head and neck and pelvic malignancies, but in patients with mediastinal malignancies the levels increased significantly more than in normals. For a given T cell level, the increase in patients with mediastinal malignancies was greater than in patients with pelvic malignancies, and as a group was greater than in patients with head and neck malignancies. The results can be explained by an increase in circulating thymosin-responsive lymphocytes during mediastinal irradiation due to suppression of a function of the thymus important for maturation of these cells, and a decrease in these cells during pelvic irradiation due to a deleterious effect on precursors in pelvic bone marrow. The results thus provide a rationale for clinical trials to assess the efficacy of thymosin in averting declines of T cell levels in patients receiving mediastinal irradiation.

Adolescent↗
PubMed1979

Cyclic nucleotide changes in murine lymphocytes following thymosin incubation in vitro.

Thymosin fraction 5 and a more purified acidic fraction of thymosin at a 100-fold lower concentration elevated cGMP levels, but not cAMP levels, in murine thymocytes. When both thymus and spleen lymphocytes were fractionated via a BSA gradient procedure, both cAMP and cGMP basal values varied depending on the density of the subpopulations. Thymosin Fr5 did not elevate cAMP in any thymus subpopulation of lymphocytes obtained from the BSA density gradients. The cGMP elevation due to thymosin Fr5 in thymocytes was maximal in the most buoyant thymocytes, and no elevation of cGMP was detected in nude mouse spleen lymphocytes. These results suggest that the cGMP elevation may be an early event in the thymosin-mediated differentiation of a more mature subpopulation of thymocytes. They also suggest that utilization of subpopulations may be necessary for the complete determination of the effects of agents on cyclic nucleotide values of lymphocytes.

Animals↗