Cells In Human Thymus Research Articles

Myoepithelial cells in human thymus: staining, polarization and fluorescence microscopic studies.

Myoid cells in human thymus were studied around the turn of the century, and alterations in patients with cardiovascular disease were reported. It was therefore deemed of interest to reinvestigate these long forgotten cells. The configurational staining, polarization and fluorescence microscopic properties of smooth myofibrils in thymic epithelial cells were identical with those of classical myoepithelial cells, smooth muscle, and A bands of striated muscle. Cross-striated myoid cells could not be found in thymus of children. Myoepithelial cells formed a layer at the surface of thymic lobules; others were scattered throughout the cortex and medulla. In addition, the medulla contained seemingly hypertrophic myoepithelial cells. Hassall's corpuscles consisted of layers of myoepithelial cells. Hammar (1905) regarded epithelial cells with smooth myofibrils in human thymus as equivalents of the cross-striated myoid cells in lower vertebrates. The myoepithelial cells observed in this study are apparently identical with the smooth myoid cells of early anatomists; the hypertrophic myoepithelial cells correspond to the unicellular Hassall's corpuscles. The functions of these cells are not yet clear; the wide variations from case to case in the same age group indicate that the myoepithelial cells are affected by a variety of diseases.

Cross-reactivity between human thymus and mouse lymphoid tissues, as revealed by rabbit antiserum against human brain.

Rabbit anti-human brain antisera were found cytotoxic for mouse thymus, lymph node, and spleen cells. Absorption with human thymus cells removed some of the cytotoxic antibodies. Cross-reactions were also detected among human brain and thymus and mouse brain, liver, and erythrocytes.

Identification and characterization: cell membrane antigens associated with the blast phase of human adult leukemia.

Cell membrane antigens which produce delayed skin reactions and are associated with the blast phase of human acute leukemia have been identified and characterized. When patients are in remission, these proteins are not present on their white blood cells. The blast antigens associated with acute lymphatic leukemia (ALL) are also present on early human fetal thymus cells. Blast antigens from acute myelocytic leukemia (AML) appear to have a different structure and are not associated with fetal antigens. The isolation away from blocking factors of purified, solubilized proteins from the leukemic blast cell membranes now permits the possibility of testing to see whether or not such specific antigens will be useful in diagnosis and in immuno-chemotherapy of leukemia.

Antibody dependent cellular cytotoxicity: Cytotoxicity mediated by non T-lymphocytes

The cytotoxic capacity of human lymphocytes in antibody dependent cellular cytotoxicity (ADCC) is mediated by non T-lymphocytes. Evidence is presented that purified peripheral blood T-lymphocytes as well as human thymus cells are inefective in ADCC. By contrast, lymphocytes bearing a receptor for immunoglobulin (Ig) effectively mediated this function.

Studies on the Human T-Lymphocyte Population

Abstract An IgG fraction of a goat antibody prepared against human thymus cells and absorbed with red blood cells, insolubilized human Ig, and cells from a patient with chronic lymphocytic leukemia (ATG) has been found to react specifically with the human T lymphocyte population (1). This antibody blocked spontaneous rosette formation by human peripheral lymphocytes and sheep red blood cells (SRBC). The F(ab′)2 and Fab′ fragments of ATG were also effective in blocking rosette formation. Moreover, capping of SRBC on lymphocytes was observed when cells were incubated with the F(ab′)2 fragment of ATG, but not with the Fab′ fragment. The data suggest that on human peripheral lymphocytes the receptor for SRBC and a T-specific antigen may be the same or may be linked. A soluble extract of human peripheral lymphocytes contained material capable of reacting with ATG. Fractions of this extract obtained from Sephadex G-200 and G-75 columns and corresponding to molecular weights of approximately 35,000 and 70,000 were capable of blocking ATD's inhibition of rosette formation. The active components appeared to be glycoproteins and migrated with Rf values of 0.96 on acrylamide gel electrophoresis.

Studies on the Human T-Lymphocyte Population

Abstract The IgG fraction of a goat antibody prepared against human infant thymus cells and extensively absorbed with pooled human red blood cells, insolubilized human Ig and cells from a patient with chronic lymphocytic leukemia (ATG), was used to study human peripheral lymphocyte populations. ATG inhibited the response of human peripheral lymphocytes to concanavalin A (Con A) but not to pokeweed mitogen (PWM). The F(ab′)2 and Fab′ fragments of ATG were as effective as ATG in inhibiting Con A induced 3H-thymidine incorporation. ATG did not interact with Con A or the receptor for Con A on the lymphocyte but was inhibitory in the absence of complement as a result of its apparent selective cytotoxicity. The antibody also inhibited 3H-thymidine incorporation in the one-way mixed lymphocyte reaction, again without affecting the response of these cells to PWM. The specificity of ATG for the T-lymphocyte population was also suggested by fluorescent labeling experiments which indicated that ATG reacted with only 50 to 80% of human peripheral lymphocytes. These results suggest that ATG is directed toward antigens unique to the human T-lymphocyte population. Moreover, it appears that ATG can be used to study human T-lymphocyte responses and to follow the isolation of T-specific antigens.

Ability of anti-brain heteroantisera to distinguish thymus-derived lymphocytes in various species

Anti-brain heteroantisera prepared in rabbits against mouse and dog brain tissues appear to distinguish T from B lymphocytes in homologous species, although some sensitivity of bone marrow cells to these antisera is also observed. Cross-reactivity of these antisera with heterologous thymus cells could not be demonstrated. The brain T lymphocyte antigen (BAθ) could not be detected in fetal mouse brain and was only present in neonatal dog brain in low concentration, increasing in concentration in a sigmoidal fashion with maturation. Rabbit antisera to human brain tissue (frontal lobe) did not have corresponding specificity for human thymus cells. Anti-mouse brain antisera are not immunosuppressive in allografted mice.

Ficoll-isopaque gradients for the determination of density distributions of human blood lymphocytes and other reticulo-endothelial cells

The interrelationship was determined between osmolarity, concentration, and density of aqueous solutions of polysucrose (Ficoll), metrizoate (Isopaque), polyethylene glycol, gum acacia, and ioglycaminic acid (Bilivistan). It was found that by mixing two solutions—each consisting of different concentrations of Ficoll, Isopaque, Tris-HCl buffer, and a Ringer solution—a linear density gradient could be produced, ranging from 1.055 to 1.095 g/ml. This gradient has a constant osmolarity of 280–290 mOsm (isotonic with human serum) and a constant pH of 7.4. A method is described for the determination of density distribution profiles of human blood lymphocytes by means of this gradient. The procedure has a high reproducibility and does not change the lymphocyte viability as determined by subsequent multiplication in culture and dye exclusion. The mean density of human blood lymphocytes, immediately after isolation, was found to be 1.072±0.0014 ( n = 12). The yield of lymphocytes from the linear gradient is 50–70 %, but can be increased to 80–90 % if 1 % human albumin is included in the gradient material. From a discontinuous gradient 80–90 % of the cells may be recovered. Moreover, it was found that the same method may be used for the determination of the density profile of human spleen cells, thymus cells, granulocytes, thrombocytes, leukaemic lymphocytes, and lymphoid line cells.

Human thymus-leukemia related antigen(s): Detection by a nonhuman primate antiserum

A nonhuman primate antiserum to human thymus cells can detect an antigen which is specific for human thymus cells. In addition, this antiserum can also detect antigens which are cross-reactive between thymocytes and cells from patients with lymphocytic leukemia and perhaps some antigens which are present on actively dividing cell populations like cultured lymphoid cell lines derived from normal individuals. The relevance of these data to other human leukemia-associated antigens and murine TL antigens is discussed.

Human lymphocyte subpopulations study of T and B cells and their density distribution

The proportions of T and B cells of various human lymphoid tissues were enumerated by sheep red blood cell and sensitized sheep red blood cells + complement rosettes. Methods using optimal temperature and time of incubation, which yielded the maximum proportion of rosettes, were used. The proportion of T cells in human peripheral blood, tonsils, spleen, thymus, and thoracic duct lymph were 72.5, 42.0, 29.3, 94.0, and 54.2%. The variations in the blood of three individuals were also studied over a period of 3–6 months. Density profiles of these tissues were analyzed by discontinuous Ficoll density gradient. The density profiles of these tissues were very similar. T and B cells were enumerated in the various fractions of the gradient. Both types were present in all the fractions analyzed, but the B cells predominate in the light density fractions, while the T cells in the heavy density fractions.

Cell-surface immunoglobulin human thymus cells and its biosynthesis in vitro.

Human thymus cells synthesize immunoglobulin in short-term culture, the nascent immunoglobulin appearing in both cytoplasmic and membrane fractions. Surface immunoglobulin was demonstrated by lactoperoxidase radioiodination of the cells. The demonstration of intracellular and surface immunoglobulin required procedures that minimize proteolytic degradation. Noncovalently linked, monomeric mu chains and light chains were found in the cytoplasm and on the surface of the cells by means of acrylamide gel electrophoresis and by specific immunoprecipitation of the isolated chains.

ATTEMPTS TO FIND A COMBINATION OF ANTIGEN CELL DOSE AND ADJUVANT WHICH RELIABLY PROVIDES IMMUNOSUPPRESSIVE HORSE ANTIHUMAN LYMPHOCYTE GLOBULIN

SUMMARY Serum from at most 3 of 7 horses immunized with fresh human thymus cells, using various cell dosages and adjuvants, prolonged skin allograft survival in rhesus monkeys. Nine additional horses subsequently immunized with graded doses of frozen thawed human thymus cells using either Freund's adjuvant, Corynebacterium parvum, or no adjuvant exhibited an antigen dose response with respect to development of lymphocytotoxic, hemagglutinating, and antiplatelet antibodies. Immunization with 10‘ or 10s thymus cells in C. parvum or Freund's complete adjuvants caused lymphocytotoxie antibodies to appear days to weeks prior to the appearance of high levels of hemagglutinating and platelet complement-fixing antibodies. None of the sera from these 9 horses, however, prolonged skin allograft survival in rhesus monkeys, although several sera caused prolonged lymphopenia. Antibodies to glomerular basement membrane were frequently identified in these sera; their appearance was not related to the antigen cell dose or adjuvant used. It is conceivable that the failure of these animals to produce effective antilymphocytic sera (ALS) may be attributable to the use of frozen thawed thymus cells as antigen. Alternatively it is possible that the horse may not be the ideal species in which to produce antithymocytic globulin for human use, both because of the low frequency with which immunosuppressive antibodies develop and the high frequency with which unwanted contaminating antibody specificities appear even after short periods of immunization.

Isolation and composition of human thymocyte plasma membrane

Plasma membrane was isolated from human thymus cells using an identical procedure with that described previously for the plasma membrane of pig lymphocytes. Its chemical and enzymic compositions, apart from a lower and more variable 5′-nucleotidase activity, were similar to those of the pig lymphocyte plasma membrane. Polyacrylamide gel electrophoresis of the human thymocyte membrane in sodium dodecyl sulphate gave a large number of protein bands about seven of which stained also for carbohydrate. A comparison of the protein and carbohydrate patterns with those of pig thymocyte and lymphocyte plasma membranes revealed a number of differences in glycoprotein composition.

Assay for the Immunosuppressive Capacity of Antilymphocyte Serum

Abstract In this and the preceding two papers an assay procedure for ALS has been described. It measures the capacity of ALS to opsonize either mouse, human or dog thymus cells. The percentage of mouse thymus cells opsonized by an anti-mouse lymphocyte serum correlates with its ability to depress the immune response of mice to SRBC. Based on this finding, it is postulated that anti-dog or anti-human lymphocyte sera that are capable of opsonizing dog and human thymus cells, respectively, will be immunosuppressive.

The Response of Cultured Human Thymus Cells to Phytohemagglutinin

Summary Studies of human thymus cells in short-term (3 to 91 hr) tissue cultures have shown the stimulation produced by phytohemagglutinin (PHA). This has been demonstrated by increased uptake of isotopically labeled DNA, RNA and protein precursors measured by autoradiography and liquid scintillation counting. The appearance of “blast cells” after culture with PHA has been shown by electron microscopy. There was wide variability from the one thymus cell preparation to another with regard to the dose of PHA and the concentration of cells per culture required for maximal isotope uptake. Thymus cells from older patients appeared to respond better to PHA than did thymus cells from younger patients. A comparison of cultures of peripheral blood leukocytes with cultures of human thymus cells indicates that at least some thymus cell preparations respond to PHA as well as do peripheral blood leukocyte preparations.

Myoid cells in adult human thymus.

MYOID cells are a common constituent of the thymus in lower vertebrates. Many recent electron microscopic studies of amphibia, reptiles and birds1–8, as well as foetal mammals3,9, confirm the presence within these cells of all the principal components of skeletal muscle.

Response of Thymus and other Human Lymphoid Tissues to PHA, PWM and Genetically Dissimilar Lymphoid Cells.

SummaryWhen human thymus, tonsil and appendix cells were exposed in vitro to PHA, PWM or allogeneic lymphoid cells for 2 to 3 days, blast cells were observed. Studies suggest that in mixed lymphoid cultures, the blast cells may have originated from both donors. Infrequently, in cultures containing transformed cells, an absence of H3-thymidine incorporation was observed by radioautography.

Lack of cytotoxicity by human thymocytes in vitro.

The phytohaemagglutinin (PHA)‐induced cytotoxic action of human blood lymphocytes against homologous cells in tissue culture was compared with the effect of human thymus cells. For quantitation of cell damage, use was made of the release of isotope from Chang cells (human liver) labelled with 51Cr‐chromate. Two young male patients with congenital heart defects served as donors. The Chang target cells were not damaged by thymic lymphoid cells added in high excess. In contrast, a small number of blood lymphocytes from the same donors tested simultaneously damaged the target cells. The thymic cells were poorly stimulated to DNA synthesis and into blastoid transformation by incubation with PHA for 3 days. PPD induced no response in the thymus cells. The blood lymphocytes reacted normally in all tests. Most thymocytes survived 24 hr inkubation while only about 25 per cent were alive after 72 hr. 70 per cent blood lymphocytes survived 72 hr incubation.It is assumed that a majority of the human thymic lymphocytes are immunologically non‐competent cells in regard to cellular immune reactivity. These cells lack cytotoxicity as well as ability to proliferate in the presence of PHA or antigens.

Comparative Response of Normal Human Thymus and Lymph Node Cells to Phytohemagglutinin in Culture

Abstract Human thymocytes, in short-term tissue culture, show a proliferative activity distinct from that observed by either lymph node or blood lymphocytes. As expected, the behavior of lymph node lymphocytes in culture is very similar to that of peripheral blood lymphocytes. The only difference between these 2 groups of cells was the finding of spontaneous proliferation by normal lymph node cells after 3 days in culture without phytohemagglutinin (PHA). Whereas blood and lymph node lymphocytes show a negligible uptake of H3T in the basal state, approximately 10 per cent of thymus cells incorporate H3T, indicating significant autonomous proliferation. This is unaffected by PHA and is unassociated with globulin synthesis as judged by immunofluorescent technics. After 3 days in culture, there are significantly more transformed cells and more cells which incorporate H3T into DNA in thymus cell cultures containing PHA than in the control cultures. However, the labeling index of stimulated thymus cultures is less than either the basal rate of proliferation of thymocytes or 3-day cultures of PHA stimulated blood and lymph node lymphocytes. These observations suggest that the normal human thymus contains at least two populations of lymphoid cells: a major component which shows autonomous and unsustained proliferative activity and does not respond to PHA, and a second and probably minor cellular component which transforms and proliferates in response to PHA.