Immunohistochemical evidences showing the presence of thymulin containing cells located in involuted thymus and in peripheral lymphoid organs

Thymulin is a well-characterized thymic hormone that exists as a nonapeptide coupled to equimolar amounts of Zn2+. Thymulin is known to have multiple biological roles, including T cell differentiation, immune regulation, and analgesic functions. It has been shown that thymulin is produced by the reticulo-epithelial cells of the thymus, and it circulates in the blood from the moment of birth, maintain its serum level until puberty diminishing thereafter in life. To study the localization of this hormone, we prepared polyclonal and monoclonal antibodies against the commercial peptide and utilized immunocytochemical techniques for visualization. The results indicate that thymulin stains the thymic reticular cells, the outer layers of Hassall's corpuscles and a large round cellular type, which is keratin-negative and does not show affinity for the common leukocyte antigen (CD-45). In mice, this thymulin-positive cell remains in the thymus throughout life and even appears in relatively increased numbers in old involuted thymi. It also appears in thymus-dependent areas of the spleen and lymph nodes, demonstrating that at least one of the thymus cells containing this peptide can be found in peripheral lymphoid tissue.

Age-related changes of thymalin content in human epidermis

Immunomorphological analysis revealed the presence of thymalin in human epidermis and in fetal reticuloepithelium. These structures are developed from the common embryonic primordium ectoderm. In embryos and adult humans thymalin is present only in young epidermal cells, which undergo age-related involution. By the age of 70 years, the layer of thymalin-containing cells looks thinned and discontinuous. The content of thymalin, a thymic factor, decreases with age.

Altered subcellular localization of suppressin, a novel inhibitor of cell-cycle entry, is an independent prognostic factor in colorectal adenocarcinomas

PURPOSE

Suppressin (SPN), a novel inhibitor of the entry into the cell cycle, has properties of a tumor suppressor gene; however, its role in the development and progression of a human malignancy is not studied. Therefore, we evaluated the status of spn and its prognostic value in human colorectal adenocarcinoma (CRC).

EXPERIMENTAL DESIGN

Inhibition of cell proliferation by exogenous/extracellular SPN was assessed by [(3)H]thymidine incorporation. The genetic status of spn in two colon cancer cell lines (LS180 and WiDr) and in a human CRC was determined using direct cDNA sequencing techniques. Phenotypic expression of SPN was evaluated in 105 CRC archival tissues using immunohistochemical methods. Univariate Kaplan-Meier and multivariate Cox proportional hazards models were used to determine the prognostic significance of SPN expression.

RESULTS

Exogenous SPN inhibited the proliferation of the LS180 cell line, which also has a mutation in one allele of the spn gene. The spn gene was also mutated in the primary CRC. Expression of SPN was primarily cytoplasmic in nonmucinous CRCs and nuclear in mucinous CRCs. However, the evaluation of 85 nonmucinous CRCs demonstrated that nuclear localization of SPN, nuclear accumulation of p53, and nodal status were independent prognostic indicators with hazard ratios of 2.34, 2.33, and 3.04, respectively. Nuclear localization of SPN plus nuclear accumulation of p53 formed a stronger prognostic indicator (hazard ratios = 5.45) than local nodal status.

CONCLUSIONS

This is the first report of genetic alterations in the spn gene in a human malignancy and suggests that genetic alterations in spn and the resulting immunohistochemical phenotypes based on SPN subcellular localization in CRCs may be useful in determining prognosis of patients with subtypes of CRC.

Review of thymic hormones in cancer diagnosis and treatment

The thymus is an endocrine organ. A unified, physiological concept of humoral regulations of the immune response has emerged in the last three decades. The thymus is the major site of production of immunocompetent T lymphocytes from their hematopoietic stem cells. This complex process required direct cell to cell, receptor based interactions, as well as in situ paracrine information via the numerous cytokines and thymic hormones produced by the cells of thymic microenvironment. Thymic hormones induce in situ T-cell marker differentiation, expression and functions. These polypeptide hormones have also been shown by means of immunocytochemistry to localize in the reticulo-epithelial (RE) cells of the thymic cellular microenvironment. Due to the great complexity of the intrathymic maturation sequence of T lymphocytes and the diverse immunophenotypically unique subpopulations of T lymphocytes, it is quite unlikely that a single thymic humoral factor could control all of the molecular steps and cell populations involved. It is much more likely that an extremely rich and diverse, but genetically determined, milieu is present within the thymus, and that thus the control of intrathymic T lymphocyte maturation and the functional maturation of T cells involves the orchestral interaction of various thymic-specific factors and other molecules during the differentiation process. Thymosin fraction 5 and its constituent peptides influence several properties of lymphocytes including cyclic nucleotide levels, migration inhibitory factor production, T-dependent antibody production, as well as the expression of various cell surface maturation/differentiation markers. Recently, derivatives of thymic hormones, mostly of thymosins, have been detected as products of neoplastically transformed cells and employed in the early diagnosis of neoplasms. In clinical trials, thymic hormones strengthen the effects of immunomodulators in immunodeficiencies, autoimmune diseases, and neoplastic malignancies. Combined chemo-immunotherapeutical anti-cancer treatment seems to be more efficacious than chemotherapy alone, and the significant hematopoietic toxicity associated with most chemotherapeutical clinical trials can be reduced significantly by the addition of immunotherapy.

Characterization of the stimulatory actions of thymic factor(s) on basal and gonadotropin-induced steroidogenesis in cultured rat granulosa cells

Recently, there have been numerous reports that demonstrate the importance of the thymus gland in reproductive physiology. Previously, we have reported that thymic factors (TFs) which are present in thymic cell culture-conditioned medium (TCM) could stimulate basal progesterone and estradiol production from cultured rat granulosa cells. The current study attempts to characterize the stimulatory actions of TFs on both basal and FSH induced steroidogenesis. Thymic epithelial cells from immature female rats were isolated and used for production of TCM. Granulosa cells were obtained from immature diethylstilbestrol (DES)-treated rats. TFs stimulated both basal and FSH-induced progesterone secretions 80 and 17 times, respectively, as compared to the control media. The effects of TFs on basal and FSH-induced 20 alpha-hydroxyprogesterone secretion were comparable to those on progesterone production (40x and 10x, respectively). In addition, TCM stimulated basal and FSH-induced estradiol secretion approximately 4 and 2.5 times, respectively, compared to control. Stimulation of aromatase enzyme activity followed a similar trend as estradiol secretion, and TCM stimulated basal and FSH-stimulated aromatase enzyme activity approximately 15 and 3 times, respectively compared to control. Thus, these results indicate that the observed increases in progesterone and estradiol secretions in TCM-treated rat granulosa cells are likely to be due to elevated activities of specific steroidogenic enzymes. Measurements of total cell protein and DNA synthesis indicate that enhanced steroidogenesis in TCM-treated cells is not due to increased cell growth and/or proliferation. Rather, the enhanced steroidogenesis is probably due to an increased steroid biosynthetic capability of the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that appearance of thymulin in plasma follows lymphoid chimerism and precedes development of immunity in patients with lethal combined immunodeficiency transplanted with T cell-depleted haploidentical marrow

Thymulin, a peptide secreted by human thymic epithelial cells, circulates in peripheral blood. Levels of plasma thymulin (FTS-Zn) activity were analyzed in 21 patients with lethal combined immunodeficiency disorders who were treated with transplantation of HLA-haplotype-mismatched parental bone marrow depleted of T cells by differential agglutination with soybean agglutinin and E-rosetting (SBA-E-BMT). Among these 21 infants, 15 were patients with severe combined immunodeficiency (SCID) and 6 had combined immunodeficiency (CID) with Omenn's syndrome or CID with T cell predominance (CIDTP). In contrast to normal infants who possess high levels of plasma thymulin activity, 20 of the 21 patients demonstrated undetectable or low plasma thymulin levels for their age at admission prior to transplantation. Following SBA-E-BMT, however, thymulin became detectable in the plasma of 17 of 18 evaluable patients and reached normal or near-normal levels between 21 and 125 days posttransplant. In patients in whom the timing of engraftment could be established by emergence of donor lymphocytes, thymulin appeared in the plasma at approximately the same time as lymphoid chimerism was detected, and in all patients who were engrafted and immunologically reconstituted, the increment in thymulin levels preceded development of immune functions. These studies support the concept that normal marrow-derived cells in the graft can provide a stimulus necessary for induction of thymic epithelial secretory function in patients with thymic dysplasia. Further, immunologic reconstitution in these patients was not seen following SBA-E-BMT unless and until recovery of thymus function had been observed.

Changes in thymocytes due to aging--a study of the effects of thymic hormone on adenine nucleotides and thymocyte DNA

The number of lymphocytes (especially T-lymphocytes) in peripheral blood decreases with aging. The decline is most evident in the thymus. In this study, total AN in the thymocytes of aged mice clearly decreases from that of young mice. The quantity of thymic hormones secreted by thymic cells decreases with the organism's thymus involution with age. After demonstrating the decrease in total AN (primarily ATP) levels within the thymocytes of aged mice, we attempted to reattain the levels of younger thymocytes by the administration of various thymic hormones. Examination of DNA in the thymocytes of 4 and 58-week-old mice, using flowcytometry, showed no differences in content. However, it is significant that aged mouse thymocytes's energy level can be returned to those of young mice with the application of Th-5.

A new radioimmunoassay for the thymic peptide thymulin, and its application for measuring thymulin in blood samples

A new, specific and sensitive radioimmunoassay, using a polyclonal antiserum raised in rabbits, is described for quantitating plasma thymulin. As little as 300 fg thymulin can be measured in one assay tube. The method has been used to measure thymulin in human blood (umbilical vessel blood, 2191 +/- 123 fg/ml; children and adults up to the age of 20 years, 1499 +/- 119 fg/ml; and adults between 21-65 years, 371 +/- 18 fg/ml). There is a highly significant decrease within these three groups (P less than 0.001 by one way analysis of variance). Also plasma thymulin levels were determined in rats (601 +/- 127 fg/ml) and in pooled plasma samples from mice (638 +/- 56 fg/ml). No thymulin was detected in plasma obtained from nude rats, nude mice and thymectomised mice. These results show that the radioimmunoassay described here is a useful quantitative tool for measuring plasma thymulin that will have applications in basic, applied and clinical research.

Biochemical characterization of thymic hormones in thymoma tissues

Thymic hormones induce T-cell markers and functions. These polypeptide hormones have also been shown by means of immunocytochemistry to localize in thymic epithelial cells. Employing biochemical isolation procedures, we have studied the concentration of two thymic hormones, prothymosin alpha and thymosin beta 4, in the thymus of three thymoma patients. After a brief boiling step, thymic tissue obtained from each patient was individually homogenized and centrifuged. The supernatant was then fractionated by gel filtration on Sephadex G-100 and further purified by reversed-phase high performance liquid chromatography (HPLC). Purified components were characterized by amino acid analysis and HPLC tryptic peptide mapping. Our results revealed that the extract from benign thymoma had both prothymosin alpha and thymosin beta 4, similar to normal human thymus. However, the thymus from a patient with invasive malignant thymoma contained only thymosin beta 4, but no prothymosin alpha. In the extract from an undifferentiated carcinoma, neither prothymosin alpha nor thymosin beta 4 could be detected. These results disclose the possible correlation of thymic hormones and the type and differentiation stage of thymomas. The inability of malignant thymic tumors to produce normal amounts of thymic hormones may contribute to their etiology. It is suggested that information on the thymic hormone content might add a new parameter to pathological diagnosis in thymic tumors.

Influence of iron-deficiency anemia on selected thymus functions in mice: thymulin biological activity, T-cell subsets, and thymocyte proliferation

To define the effects of iron deficiency on thymulin biological activity, T-cell subsets, and thymocyte proliferation, C57BL/6 female mice at weaning were fed an iron-deficient diet (10 mg Fe/kg diet), an iron-sufficient diet (50 mg Fe/kg diet), or restricted amounts of the iron-sufficient diet (the pair-fed group) for 40 d. Iron deficiency did not reduce the concentration of either serum or intracytoplasmic thymulin. Although T-cell subsets in the thymus were not altered, both the cortical and medullar regions were depleted of thymocytes. In the spleen iron deficiency (but not underfeeding) significantly reduced the percentage of L3T4+ cells, of Lyt-2+ cells, and thus of the overall T-cell population. However, it did not affect the ratio of L3T4+ to Lyt-2+ T cells. Thymocyte proliferation was significantly reduced at the concanavalin A (Con A) dose (10 mg/L) that produced maximal stimulation in control and pair-fed mice but not at low (7.5 mg/L) or high (15 mg/L) Con A concentrations. We conclude that the impairment in immune functions associated with iron deficiency is not due to an impairment in thymic endocrine function but rather to decreased immunocompetent lymphocytes.

Human epithelial thymic tumours: heterogeneity in immunostaining of epithelial cell markers and thymic hormones

Different hormones (thymulin, thymosin alpha 1, vasopressin), antigenic markers of cortical and subcapsular/medullary thymic areas and tumour associated antigens were studied on paraffin or frozen section and cultures of human epithelial thymic tumours ('thymomas'). Thymulin, thymosin alpha 1 and for the first time vasopressin are found in most tumours. The epithelial cells of five 'thymomas' had markers of both cortical (TE3) and subcapsular/medullary thymic regions (A2B5 and/or TE4 and/or anti-p19). Leu-7, a marker of subcapsular epithelial cells was positive only in two tumours. The histological classification into cortical and medullary tumours does not correspond to our immunofluorescence results. The presence of these markers does not support the theory of different embryologic origin of the cortical and subcapsular/medullary epithelial cells. Transferrin receptors were detected on only some epithelial cells of thymic 'carcinomas'. Adenocarcinoma related antigen and carcino embryonic antigen only stained a few epithelial cells of all the tumours. There is no expected correlation between the presence of epidermal growth factor receptors on cell membranes and the number of proliferative cells stained by the anti-Ki67 antibodies. Immunostainings were heterogeneous according to the epithelial thymic tumours, independent of histological classification and not yet useful for prognosis.

Male BXSB mice develop a thymic hormonal dysfunction with presence of intraepithelial crystalline inclusions

The thymus is morphologically abnormal in male BXSB mice with cortical involution densification of the epithelium and the presence of intraepithelial crystals. The thymic endocrine function in BXSB mice was appraised using a biological assay to measure the level of the zinc-dependent thymic hormone, thymulin, and an indirect immunofluorescence technique to evaluate the number of cells synthesizing the hormone within the thymus. Unlike the dramatically accelerated age-linked decline of thymulin production reported in females of other autoimmune strains (measured as early as 6 weeks of age), only male BXSB were affected, as compared to normal strains. The number of hormone-producing cells was significantly reduced in male BXSB thymuses, in parallel with this hormonal decrease. Thymulin inhibitory molecules were detected in male BXSB sera, as early as 8 weeks of age, as evaluated by their capacity to absorb in vitro and in vivo the biological activity of the hormone. These inhibitors are thymus dependent since they disappear after adult thymectomy. They are low MW molecules (less than 10 kDa), as previously found in normal aging mice, rather than autoantibodies, as evidenced in two autoimmune strains (B/W and db/db mice). These findings demonstrate that male BXSB mice develop thymic abnormalities very similar to those observed in other autoimmune strains. The presence of intrathymic crystals and of low MW inhibitors suggests the role of abnormal storage and the excretion of thymulin. This thymic dysfunction may play a role in the maintenance of B cell hyperactivity previously shown in BXSB males.

Establishment of the specific radioimmunoassay for serum thymic factor (STF)

Serum thymic factor is a humoral factor involved in the differentiation of T cells. In the present study, a radioimmunoassay system for STF was established using a specific antiserum and an iodinated synthetic STF as a tracer. Serum levels of STF-like immunoreactivities were around 30 pg/ml in human, but in contrast to previous reports serum STF levels did not show age-dependent decreases. STF-like immunoreactivities of the thymic gland were lower than those of the liver and kidney in rats. The livers of human and pig contained high STF-like immunoreactivities. The rat thymic gland extract showed three peaks of STF-like immunoreactivity by gel filtration of Sephadex G-25 which corresponded to the eluted position of authentic STF, a larger molecular size, and a smaller molecular size of STF, respectively, while the rat liver extract showed two peaks corresponding to the void volume fraction and to the position of authentic STF, respectively. When this void volume fraction was digested by trypsin, three peaks which corresponded to authentic STF, a larger molecular size, and a smaller molecular size of STF were observed. Present studies suggest that serum thymic factor is produced as a larger STF molecule in the liver and kidney.

The distribution and structure of FTS immunoreactive cells in the thymus of the mouse

The intrathymic distributions of facteur thymique sérique (FTS)-containing cells and Ia-expressing cells were examined by a double immunofluorescence technique in C57BL/6 mice of various ages. In the thymic medulla of all the mice examined, there were both FTS-immunoreactive cells and Ia-immunoreactive cells. The former cells, epithelial in nature, extended elongate cytoplasmic processes, while the latter were connected with each other by their spiny processes. The FTS-immunoreactive epithelial cells were all Ia-negative. The FTS-immunoreactive cells and Ia-immunoreactive cells were located in close proximity to each other. The cortex of the adult mice contained no FTS-immunoreactive epithelial cells. The cortex of the newborn and old mice, however, contained scattered FTS-immunoreactive epithelial cells with processes. FTS-immunoreactive cells in the cortex of the old mice possessed Ia-immunoreactive partner cells, while those in the cortex of newborn mice did not. In the marginal zone of the medulla of old mice, there were several cavities bounded by a partly ciliated epithelium and containing lymphocytes. The epithelial cells lining the cavities showed intense immunofluorescence for FTS. In addition to the epithelial cells, a certain population of round cells with thin cytoplasm lacking in discernible processes immunofluoresced for FTS. Located both in the medulla and in the cortex, these round cells were postulated to be thymocytes, the target cells of FTS, binding FTS on their cell surface.

Thymulin (facteur thymique serique) and zinc contents of the thymus glands of malnourished children

Protein-energy malnutrition (PEM) leads to an immune deficiency, which is now well documented. Some investigators have suggested that the associated zinc deficiency is important in thymic involution and changes in cellular immunity. To evaluate the respective roles of nutritional deficiency, infection, and zinc in the alteration of thymic function, we measured the amounts of thymulin (facteur thymic serique, or FTS) and of Zn in the thymus glands of 58 Senegalese children who died in various stages of malnutrition. In the severe forms (marasmus, kwashiorkor, and marasmic kwashiorkor) the thymus was tiny and contained very little thymulin. The Zn content of the thymus was high whatever the nutritional state of the subject and was related significantly only to the presence of infections. In Senegalese children thymic atrophy and depleted thymulin content are associated with severe PEM but not systemic infection or depleted thymic Zn content.

[Immunochemical identification and study of interspecies thymus antigen-2]

A new interspecific animal thymus antigen (AgT-2) was identified. It was shown that AgT-2 is a microglobulin with a molecular mass about 12 kDa, electrophoretic mobility of alpha 1-globulins and isoelectric point of 4.6. Heating of the protein to 80 degrees C for 30 min did not lead to the loss of its immunochemical activity. AgT-2 was identified in extracts of bovine fetal thymus, spleen and liver. It was discovered in the extracts of the lung and colon of adult animals. Cross-reactions were found between bovine, walrus, deer and chicken AgT-2. This fact confirms that AgT-2 is interspecies-specific. AgT-2 was not identified in men, dogs, mice, rats and rabbits. Immunochemical research of immunocorrecting preparations revealed that AgT-2 is a constant component of T-activin, thymalin, thymosin and TP1-Serono and its concentration varies from 1.6 to 3.2%. It has been stated that immunochemical test for AgT-2 can be used as a marker in the production and standardization of active thymus factors.

Immunolocalization of thymosin alpha 1, thymopoietin and thymulin in mouse thymic epithelial cells at different stages of culture: a light and electron microscopic study

The secretory evolution of the thymic hormones (thymulin, thymosin alpha 1 and thymopoietin) in cultured thymic reticuloepithelial cells (TREC) was studied by immunocytochemical techniques using monoclonal anti-thymulin or anti-thymosin alpha 1 and polyclonal anti-thymopoietin antibodies (Ab). The culture of TREC was performed with a medium where L-valine was replaced by D-valine, thus ensuring rapid and selective development of these cells. The number of thymulin, thymosin alpha 1 or thymopoietin-containing cells increased progressively from Day 6 to Day 12 of the culture. The localization of the three thymic hormones within the TREC also varied according to the age of the culture. By light microscopy the staining of the three hormones was localized in some cytoplasmic granules at the beginning of the culture and at Day 90, while at Day 12 it was throughout the cytoplasm. In electron microscopy these localizations corresponded respectively to vacuoles of different sizes and to cytosol. All these results show that the synthesis and excretion of thymulin, thymosin alpha 1 and thymopoietin evolve during the development of TREC in culture.

An enzyme immunoassay for synthetic thymulin

Thymulin, a metallononapeptide with the following aminoacid sequence: pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-AsnOH is a thymic hormone involved in T cell differentiation requiring zinc to express biological activity as measured by the rosette assay. We established an enzyme immunoassay (EIA) for synthetic zinc-free thymulin with a thymulin-acetylcholinesterase conjugate as tracer and specific polyclonal rabbit antithymulin antibodies. The assay is performed as a classical competition assay in microtiter plates previously coated with mouse monoclonal IgG to rabbit IgG. A quantitative thymulin assay more sensitive than radioimmunoassays (RIAs) previously described was obtained with a sensitivity (IC50) of 32.5 +/- 5 pg/ml and a detection limit of 5 pg/ml. Analysis in the EIA of synthetic thymulin analogs showed that the minimal peptidic structure necessary for enzymatic tracer competition is the C-terminal part Lys3 to Asn9. It was also shown that the biologically active form of thymulin (zinc-bound) has the same immunoreactivity as zinc-free thymulin and that other thymic hormones, thymosin alpha 1 and thymopoietin II (or TP5) and unrelated short peptides do not cross-react with thymulin. These data demonstrate the specificity of this EIA for thymulin and show its suitability for application in biological fluids.

[Immunoenzyme method of determining thymus polypeptide factor]

A rapid indirect enzyme immunoassay technique for the determination of thymalin, a polypeptide thymus factor, with sensitivity equal to 1.5 X 10(-8) mol/l has been developed. The accuracy of determinations, measured by the variation factor, has proved to be 5-10% in the interassay, 10-15% in the interassay, the reliability in the opening test being 5%. The assay takes 4.5-5 hours.

Thymic dysfunction in histiocytosis-X

In some patients with histiocytosis-X there is a deficiency of suppressor T cells, which is corrected in vitro by incubation with either crude calf thymic extract or thymostimulin. This finding suggests that a thymus deficiency could be involved in this disease. Low levels of serum thymic factor (FTS) are found in patients with histiocytosis-X. Their plasma contain factors capable of inhibiting biological activity of FTS in vitro. Elucidation of the mechanism by which FTS is inhibited would be helpful in understanding the immunological defect in histiocytosis-X. The presence of evidence of thymic dysfunction and the fact that patients respond to thymic hormone therapy suggest that histiocytosis-X could be due to a primary immunodeficiency syndrome. Thymulin, which stimulates the generation of suppressor T cells, could be of benefit in therapy.

Circulating thymic hormone activity in young cancer patients

We measured serum levels of Facteur Thymique Sérique (FTS) in 56 young cancer patients compared to normal controls. All patients who received immunosuppressive therapy had low age-corrected titres of FTS. Low levels were also found at diagnosis and off therapy. Plasma from 22 patients contained factors capable of inhibiting biological activity of FTS in vitro. The nature of this inhibitor has not been elucidated. No zinc deficiency was found in the patients studied, suggesting that FTS is secreted in its active form. Our study points out the importance of monitoring FTS activity in young cancer patients for its implications on immunological surveillance. The practical applications of thymic hormone therapy in cancer patients are discussed.

Immunoreactive thymopoietin in the mouse central nervous system

A thymopoietin-immunoreactive substance (TP-IRS) has been detected in homogenates of mouse spinal cord and brain using a radioimmunoassay; levels were maximal at birth. TP-IRS was also detected in supernatants of mouse neuroblastoma (NIE-115) and primary spinal cord cultures but not human astrocytic and meningeal tumors or mouse primary astrocyte cultures. With affinity purified rabbit anti-TP globulin, immunofluorescent staining was seen in mouse spinal cord cultures in association with nuclear membranes of neurons and, to a lesser degree, flat background cells. From supernatants of NIE-115 cells grown in tritiated leucine and lysine, proteins of approximately 8000 and 4500 Da were isolated by TP affinity chromatography (compared with 5562 Da for thymic thymopoietin). When injected into mice, these neural proteins partially blocked neuromuscular transmission in a manner similar to thymic thymopoietin.

Mammalian single-stranded DNA binding protein UP I is derived from the hnRNP core protein A1

Antibodies induced against mammalian single-stranded DNA binding protein (ssDBP) UP I were shown to be cross-reactive with most of the basic hnRNP core proteins, the main constituents of 40S hnRNP particles. This suggested a structural relationship between both groups of proteins. Using the anti-ssDBP antibodies, a cDNA clone (pRP10) was isolated from a human liver cDNA library in plasmid expression vector pEX1. By DNA sequencing this clone was shown to encode in its 949 bp insert the last 72 carboxy terminal amino acids of the ssDBP UP I. Thereafter, an open reading frame continued for another 124 amino acids followed by a UAA (ochre) stop codon. Direct amino acid sequencing of a V8 protease peptide from hnRNP core protein A1 showed that this peptide contained at its amino terminus the last 11 amino acids of UP I followed by 19 amino acids which are encoded by the open reading frame of cDNA clone pRP10 immediately following the UP I sequence. This proves that ssDBP UP I arises by proteolysis from hnRNP core protein A1. This finding must lead to a re-evaluation of the possible physiological role of UP I and related ssDBPs. The formerly assumed function in DNA replication, although not completely ruled out, should be reconsidered in the light of a possible alternative or complementary function in hnRNA processing where UP I could either be a simple degradation product of core protein A1 (as a consequence of controlling the levels of active A1) or may continue to function as an RNA binding protein which has lost the ability to interact with the other core proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical characterization of the thymic microenvironment. A light-microscopic and ultrastructural immunocytochemical study

The epithelial framework of the human thymus has been studied in parallel by immunohistochemical methods at the light- and electron-microscopic levels. Different monoclonal antibodies were used, reacting with components of the major histocompatibility complex, keratins, thymic hormones and other as yet antigenically undefined substances, which show specific immunoreactivities with human thymus epithelial cells. The electron-microscopic immunocytochemical observations clearly confirm microtopographical differences of epithelial cells not only between the thymic cortex and medulla, but also within the cortex itself. At least four subtypes of epithelial cells could be distinguished: 1) the cortical surface epithelium; 2) the main cortical epithelial cells and thymic nurse cells; 3) the medullary epithelial cells; and 4) the epithelial cells of Hassall's corpuscles. The various epithelial cell types of the thymus display several common features like tonofilaments, desmosomes and some surface antigens as demonstrated by anti-KiM3. In other respects, however, they differ from each other. The cortical subtype of thymic epithelial cells including the thymic nurse cells shows a distinct pattern of surface antigens reacting positively with antibodies against HLA-DR (anti-HLA-DR) and anti-21A62E. Electron-microscopic immunocytochemistry with these antibodies clearly reveals a surface labeling and a narrow contact to cortical thymocytes particularly in the peripheral cortical regions. An alternative staining pattern is realized by antibodies to some antigens associated with other subtypes of thymic epithelial cells. Medullary epithelial cells as well as the cortical surface epithelium react likewise positively with antibodies to special surface antigens (anti-Ep-1), to special epitopes of cytokeratin (anti-IV/82), and to thymic hormones (anti-FTS). The functional significance of distinct microenvironments within the thymus provided by different epithelial cells is discussed in view of the maturation of T-precursor cells.

Melatonin, thymic serum factor, and cortisol levels in healthy subjects of different age and patients with skin melanoma

Results are given of daily excretion levels of 6-oxymelatonin, thymic serum factor (FTS), and cortisol in the blood of 140 healthy subjects and 90 patients with skin melanoma, ranging from 20 to 49 years of age. Correlation factor (eta) was used for evaluating the correlation between the indices examined. Daily excretion of 6-oxymelatonin was found to decrease considerably in healthy men over 30 years of age, the extent of such reduction correlating with age (eta = 0.48 +/- 0.19, P less than 0.02). Similar correlation is absent in healthy women. There is an age-related reduction in FTS in both healthy women (eta = 0.63 +/- 0.13, P less than 0.001) and men (eta = 0.57 +/- 0.12 P less than 0.001), although in the latter this reduction occurs 10 years earlier (beginning at 30 years) and is more pronounced. Blood cortisol levels in healthy subjects increase with age, more notably in men than in women. Age-related changes in the content of the hormones under study are still more pronounced when patients of corresponding age groups develop neoplasms. Male patients from 20 to 29 and 30 to 49 years of age with melanoma show daily levels of 6-oxymelatonin excretion of 10.13 +/- 0.71 micrograms/24 hr and 11.70 +/- 1.26 micrograms/24 hr, respectively, while healthy men of the same age show much higher melatonin levels, i.e., 18.98 +/- 1.36 micrograms/24 hr and 15.46 +/- 1.13 micrograms/24 hr, respectively. Male melanoma patients aged 30 to 49 years have reduced log2 of FTS titers (as little as 1.44 +/- 0.23) compared to that of healthy, age-matched males (3.40 +/- 0.23, P less than 0.05). In female patients aged 20-39 years and 40-49 years, the log2 of FTS titers was 1.96 +/- 0.37 and 1.62 +/- 0.25, respectively, which is significantly lower (P less than 0.05) than values for healthy women of the same age (5.60 +/- 0.17 and 3.60 +/- 0.41). In melanoma male and female patients from 20 to 49 years of age, cortisol levels are significantly higher than the mean values for this hormone in age-matched healthy subjects, being 193.18 +/- 19.67 ng/ml and 135.43 +/- 14.36 ng/ml, respectively (with normal levels of 140.60 +/- 9.62 ng/ml and 101.03 +/- 8.61 ng/ml). The results of correlation analysis indicate that daily excretion values for 6-oxymelatonin in healthy subjects correlate with both FTS titers and cortisol content, while the latter two correlate with each other (P less than 0.05). Statistically significant correlation between the levels of all examined hormones was found in melanoma patients as well (P less than 0.05).

Preparations of homeostatic thymus hormone consist predominantly of histones 2A and 2B and suggest additional histone functions

The two major constituents in preparations of the homeostatic thymus hormone (HTH) were purified. Amino acid sequence analysis showed that the components (HTH alpha and HTH beta) are identical to histones H2A and H2B, suggesting the possibility that histones might have hitherto unrecognized occurrence and functions. If the HTH activities are not ascribed to the two histones in the preparation, they could only be derived from minor constituents present in minimal amounts. Therefore, the histone structures were scrutinized for properties of relevance in relation to hormone activities and for similarities with thymic hormones. Similarities between COOH-terminal regions of histones H2A, H2B, and H3 were noticed, as well as some similarities between NH2-terminal regions of histones and parts of recognized thymus hormones and related proteins. Potential signals, resembling cleavage sites in prohormones, are present in the histone structures, and further correlations with recently discovered ubiquitin functions may explain molecular mechanisms for actions of the HTH preparations. None of the observations is significant by itself, but the combined results suggest the hypothesis of different relationships and functions, including hormone-like activities, for some histones.

Thymopentin structure and relation to thymic factors

High-performance liquid chromatography (HPLC) was used to evaluate the purity and batch-to-batch consistency of four commercially available thymic extracts and thymopentin, the synthetic pentapeptide corresponding to the biologically active region of the thymic hormone thymopoietin. The thymus extracts were all extremely heterogeneous, differing one from the other. Additionally, they showed high batch-to-batch variation. In contrast, thymopentin was homogeneous and this homogeneity was consistent in different batches.

Thymic hormone-containing cells VI. Immunohistologic evidence for the simultaneous presence of thymulin, thymopoietin and thymosin alpha 1 in normal and pathological human thymuses

The localization of the three best-defined thymic hormones, namely, thymulin, thymopoietin and thymosin alpha 1 was studied by immunofluorescence using antibodies directed against these three molecules. With both human thymus frozen sections and cultured cells, thymic hormones were found exclusively in the epithelial component (recognized by its keratin content), in normal as well as pathological thymuses. The double-labeling experiments using the different anti-thymic hormone antibodies showed that the same epithelial cells contained the three hormones. These results suggest that the production of different hormones in the thymus is accomplished by the same epithelial cells.

Thymopoietin radioreceptor assay utilizing lectin-purified glycoprotein from a biologically responsive T cell line

Radiolabeled thymopoietin that was biologically active and of high specific activity was prepared by a novel technique involving protection of free amino groups, selective excision of the protected N-terminal prolyl group with post-proline cleaving enzyme, reaction of the newly exposed alpha-amino group with a highly radioiodinated compound, and deprotection and purification of the polypeptide. Binding of this radiolabeled thymopoietin was not demonstrable by conventional techniques with cells, cell membranes, or solubilized cell membranes, apparently due to the presence of active proteases in these preparations. A glycoprotein with thymopoietin binding properties was prepared by lectin purification from the detergent-solubilized membranes of CEM cells, a human T cell line that responds to thymopoietin in vitro with increases in intracellular cyclic GMP. Presumably this procedure separated the thymopoietin binding protein from membrane proteases, thus permitting the development of a radioreceptor assay. Evidence is presented that the thymopoietin binding protein represents a thymopoietin receptor that is probably related to the mediation of immunoregulatory actions of thymopoietin on a subset of peripheral T cells.

Thymic hormone-containing cells. V. Immunohistological detection of metallothionein within the cells bearing thymulin (a zinc-containing hormone) in human and mouse thymuses

Using an immunofluorescence (IF) assay, the presence of metallothionein (MT) was investigated in sections of normal and pathologic human thymuses as well as in cultures of thymic epithelial cells. This protein, known to have a high binding affinity for class II B transitional metals, such as zinc, was detected in the epithelial component of the thymus. Moreover, double labeling experiments with the anti-MT and an anti-thymulin monoclonal antibody showed that all cells containing thymulin, a thymic hormone whose active structure is known to contain zinc, also exhibited large amounts of metallothionein. These results, together with the fact that zinc and thymulin have been detected in the same type of cell organelles, lead to the conclusion that the MT present in thymic epithelial cells might be involved in the mechanism of zinc storage in these cells, thus favoring the secretion of thymulin in its biologically active, zinc-containing form.

Radioimmunoassay of serum thymic factor (FTS)

We established a radioimmunoassay (RIA) method which enables a quantitative estimation of serum thymic factor (FTS). This assay is based on the displacement of 125I-(Lys[Tyr] 3)-FTS bound to the anti-FTS antibodies by FTS. Formaldehyde-fixed Staphylococcus aureus Cowan I cells were used to precipitate the antigen-antibody complex. The anti-FTS antiserum was raised in rabbit by repeated injections of FTS-conjugated bovine serum albumin. The antiserum seemed to recognize the carboxy-terminal seven amino acid residues, Lys-Ser-Gln-Gly-Gly-Ser-Asn-OH, of the FTS molecule. As little as 0.5 to 1 pg FTS can be detected by this method. To measure the FTS content in the serum, a serum sample was pretreated with 10% trichloroacetic acid and then with ethanol for removal of serum proteins. The FTS content in pig serum was around 22 pg/ml, and that in BALB/c mouse serum was 1.3 pg/ml. The FTS contents in the sera of DBA/2, C57BL/6 and (C57BL/6 X DBA/2)F1 mice were also less than 5 pg/ml. Since more than 70% of FTS exogenously added to pig or mouse serum was recovered, the mouse serum probably contains only a small amount of FTS.

Effects of in vivo Friend leukemia virus infection on levels of serum thymic factors and on selected T-cell functions in mice

The levels of serum thymic factor(s) (STF), of Thy-1.2 positivity of splenocytes [as measured by their azathioprine (AZ) sensitivity], and of Thy-1.2-positive "spontaneous" spleen rosette-forming cells (SSRFCs), as well as the presence of infectious virus in the thymus, were assessed as a function of time after virus inoculation in susceptible DBA/2, partially resistant BALB/c, and fully resistant C57BL/6 mice given the polycythemia- or anemia-inducing strain of Friend leukemia virus (FLV-P and FLV-A, respectively). As early as Days 2 to 3, the levels of STF and of AZ sensitivity of splenocytes were profoundly decreased in DBA/2 mice, and, to a lesser extent, in BALB/c mice given FLV-P; however, SSRFCs/spleen were increased in both mouse strains. Conclusive evidence of infectious FLV-P was obtained in the thymuses of DBA/2 mice soon after infection. In mice of the same strains infected with FLV-A, STF levels were similarly decreased, but AZ sensitivity of splenocytes was unaffected, and SSRFCs were decreased. Evidence of early FLV-A infection in the thymus of DBA/2 mice was likewise obtained. In C57BL/6 mice given FLV-A, STF levels, AZ sensitivity of splenocytes, and SSRFC showed changes similar to, but of lower magnitude than, those in BALB/c mice. On the other hand, in C57BL/6 mice given FLV-P, the decrease in STF and AZ sensitivity was almost as pronounced as in susceptible DBA/2 mice in the face of complete absence of infectious virus or viral markers in the thymuses. The observed changes are ascribed to virus infection in view of the following: (a) good temporal correlation between these changes and virus infection; (b) absence of any change in mice given heat-inactivated viruses or spleen homogenate of normal DBA/2 mouse spleen; (c) overall good correlation between mouse genotype and genetic (Fv-1 and Fv-2) restrictions of virus infection on one hand and the magnitude of the observed changes on the other. In particular, the decrease in STF and SSRFC levels is ascribed to the replication-competent (Friend-murine leukemia virus) component of Friend leukemia virus complex, whereas the decrease in AZ sensitivity of splenocytes and the increase of SSRFCs are ascribed to the defective spleen focus-forming virus component of the complex. All changes described so far were transient, since they were not detectable beyond 42 days after virus inoculation in overtly leukemic animals. The observed derangements of thymus-derived immune functions may play an important cofactor role during the onset of leukemia in mice genetically permissive to Friend leukemia virus replication and transformation, but they do not seem relevant to the maintenance of leukemia.

Thymopoietin-like substance in human skin

A heterologous antithymopoietin (anti-TP) antibody was used to determine whether a TP-like molecule is present in the epidermis, since such factors have been postulated to play a part in known T cell-epidermal cell interaction. Examination of cytocentrifuge smears of freshly separated human epidermal cells stained by indirect immunofluorescence revealed that 8-14% of these cells possessed cytoplasmic reactivity with the anti-TP antibody. Similarly, 2-5% of human epidermal cells, maintained in tissue culture for 2-8 weeks, showed cytoplasmic staining with the anti-TP antibody. Double-labeling immunofluorescence studies, with the anti-TP antibody and a monoclonal antibody specifically reactive with Langerhans cells (OKT6), demonstrated that cells possessing this TP-like substance were not Langerhans cells. In situ studies of 4-microns frozen sections of normal human skin indicated that the cell population which possesses the TP-like substance is the basal layer of keratincoytes in the epidermis.

Regulatory effects of thymus humoral factor on T cell growth factor in aging mice

The effect of thymus humoral factor (THF) on T cell growth factor (TCGF) production by T cells and the association between splenic macrophages and T cells from young (2-3 months) and old (20-24 months) mice in this respect were studied. Splenocytes were divided into three groups: stimulated with concanavalin A (Con A); preincubated with THF and then stimulated with Con A; or stimulated with Con A and thereafter incubated with THF. These cells were then examined for production of TCGF. Cells treated with Con A and THF as described above were passed on nylon wool to enrich T cell populations and added to mitogen-sensitized (Con A or lipopolysaccharide) adherent splenocytes of old and young mice in the following combinations: young adherent and young T cells; young adherent and old T cells; old adherent and young T cells; and old adherent and old T cells. The results demonstrated that: (A) cells of old mice produced less TCGF than the young; (B) preincubation of splenocytes or nylon-wool enriched T cells with THF increased the production of TCGF consistently in young mice, whereas in the old a significant increase was observed only in some cases; (C) depressed TCGF activity was observed when treatment with THF to splenocytes or nylon-wool enriched T cells from young and old mice was performed after Con A stimulation, and this was also more pronounced in the young; (D) the reduced level of TCGF in the old seemed to be related to a lesion in the T cell compartment, since adherent cells from old and young mouse spleens could support TCGF production by T cells from young mice and not from old.

Measurement of thymosin alpha 1 by disassociation microELISA

A disassociation microELISA was devised for the estimation of thymosin alpha 1, a chemically characterized thymic polypeptide isolated from bovine thymosin fraction 5. Antiserum to synthetic thymosin alpha 1 was raised in rabbits. Thymosin alpha 1 in liquid phase competed with a solid-phase-bound thymosin alpha 1 for this highly specific antibody. The method is specific, sensitive, reproducible and capable of detecting as little as 100 pg/ml of thymosin alpha 1.

Demonstration of abnormalities in expression of thymic epithelial surface antigens in severe cellular immunodeficiency diseases

Thymic epithelium from three patients with severe cellular immunodeficiency diseases were compared with age-matched normal thymic epithelium using three markers of human thymic epithelium and antibodies against thymosin alpha 1, thymopoietin, and thymosin beta 4. We have previously shown that normal thymic epithelium reacts with antibodies against GQ gangliosides (antibody A2B5) and binds tetanus toxin (TT). In addition, some areas of normal thymic epithelium express human Thy-1 antigen. We found thymic epithelium in patients with severe cellular immunodeficiency diseases to be different from normal subjects. Two children with severe combined immunodeficiency disease (SCID) had thymic epithelium that bound anti-GQ ganglioside antibody but, unlike in normals, did not bind TT. The patient with severe cellular immunodeficiency and normal serum immunoglobulins (Nezelof syndrome) had thymic epithelium that bound TT but, unlike normal thymic epithelium, did not react with anti-GQ ganglioside antibody. Thymic epithelium from both SCID and Nezelof syndrome patients contained thymosin alpha 1, thymopoietin, and thymosin beta 4 and expressed human Thy-1 antigen. In contrast to SCID thymus rudiments, Nezelof thymus contained numerous (though fewer than normal) lymphocytes with mature T cell surface antigens. Thus, using these probes of human thymic epithelium, we have demonstrated heterogeneous defects in thymic epithelial surface marker expression in severe primary cellular immunodeficiency diseases. These defects presumably reflect abnormalities of in vivo thymic epithelial maturation.

Immunoglobulin levels, T-cell markers, mitogen responsiveness and thymic hormone activity in Turner's syndrome

Immunoglobulin levels (IgG, IgA, IgM), percentage and number of circulating B and T lymphocytes, mitogen responsiveness (PHA and Con A) and activity of thymus-dependent serum factor (SF) were estimated in 29 patients with Turner's syndrome (TS), ranging in age from 2.2/12 to 18.4/12 yr. IgG and IgM were decreased in 14 and 12, respectively, while IgA was very low in 1, and increased in 7. Peripheral blood B and T lymphocytes, in vitro responsiveness to PHA, and Con A, and SF activity were in the normal range. The present immunological study suggests that TS is often associated with low levels of serum IgG and IgM. The possible mechanism of these derangements, whether genetic or hormonal (low estrogen/androgen ratio), is discussed.

Radioimmunoassays for the thymic hormone serum thymic factor (FTS)

Four radioimmunoassays (RIA) are described for the quantitation of serum thymic factor (facteur thymique serique, FTS), a thymic peptide hormone. Each assay employs an antibody specific for FTS, synthetic FTS (Glp-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) as the hormone standard, and a radioiodinated FTS analogue as the tracer. Since FTS lacks a tyrosine residue, 2 FTS analogues were synthesized by the solid-phase method with tyrosyl-alanyl or 3-(2,6-dichlorobenzyl)tyrosyl-alanyl in place of the amino-terminal pyroglutamyl residue (Glp). They showed full FTS immunoreactivity and their radioiodinated derivatives served as FTS tracers. Two assays used the antiserum from a rabbit immunized with an FTS-protein conjugate. Two other assays used a monoclonal antibody against FTS produced by a hybridoma derived from mouse myeloma cells and splenocytes from a BALB/c mouse immunized with an FTS-mouse IgG conjugate (Ohga et al., 1982). All 4 RIAs were specific for FTS. The more sensitive rabbit antiserum can detect as little as 1 pg of FTS in a 50 microliters sample, which may allow quantitation of the FTS circulating in human peripheral blood.

Search for thymocyte growth-stimulating activity in extracts of different tissues and among established growth factors and thymic maturation hormones

A thymocyte specific growth factor has previously been prepared from calf thymus. Similar activity is now shown to be present in thymus and spleen of guinea pigs, but not in lymph nodes, liver and kidney. Purified thymic maturation hormones, interleukins and several growth factors for other cell types than lymphocytes were tested and found not to stimulate DNA synthesis of thymocytes. A slight activity was found in thymosin fraction 5, known to contain at least 35 polypeptides. Our factor lacked comitogenic effect when tested in combination with concanavalin A (Con A) and phytohemagglutinin, did not promote continuous growth of ConA-induced lymphoblasts and did not affect the cyclic AMP level of thymocytes. The data indicate that our factor is functionally distinct from the purified hormones and defined factors tested.

Identification of FTS (facteur thymique serique) on thymus ultrathin sections using monoclonal antibodies

Using a new immunoelectromicroscopical technique, this study confirms the localization of the 'facteur thymique sérique' (FTS) in the reticulo-epithelial cells of mouse thymus. The use of anti-FTS monoclonal antibodies on ultrathin sections for electron microscopy reveals FTS in cytoplasmic vacuoles, labelling density depending on the density of the vacuolar content. The successful application of this technique opens the way to its use for double-immunolabelling.

Thymic hormone-containing cells. Characterization and localization of serum thymic factor in young mouse thymus studied by monoclonal antibodies

The characterization and distribution of cells containing the serum thymic factor (FTS) in the thymus of young mice was studied by immunofluorescence using monoclonal anti-FTS antibodies. FTS+ cells were distributed throughout the thymic parenchyma but were more frequent in the medullary region than in the cortex. FTS-containing cells presented a stellate or globular aspect, and some of them exhibited fluorescent cytoplasmic granules. The epithelial nature of FTS+ cells was confirmed by double-labeling experiments using an anti-keratin antiserum (as an epithelial cell marker). Nevertheless, only a minority of keratin-positive epithelial reticular cells contained FTS. All controls, including the incubation of sections from nonthymic tissues with the anti-FTS antibodies, were negative. Taken together, these results confirm the exclusive localization of FTS-containing cells within the mouse thymus.

Location of FTS (facteur thymique sérique) in the thymus of normal and auto-immune mice

This study was concerned with the in situ localization of facteur thymique sérique (FTS) by immunoelectron microscopy in the thymus of normal C57BL mice and aged auto-immune SWAN mice. Normal young mice have anti-FTS antibodies fixed specifically on the floccular material present in the cytoplasmic vacuoles of epithelial cortical and medullary cells. In aged auto-immune SWAN mice the anti-FTS antibodies show an activity only in the granules present in the vacuoles or free in the cytoplasm of epithelial cells. The floccular material is not labelled by the same antibodies. FTS positive granules show a repetitive structure which is characteristic of crystalline protein formations. The presence of FTS in the granules of cells confirm the hypothesis of FTS storage in the cytoplasm of epithelial cells in vivo during the auto-immune process.