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Biomedical subjects

C Sorg

Publications and source records attributed to C Sorg.

At least 235 records · Page 13Linked to original sources
PubMed1979

The biochemistry and in vitro activity of soluble factors of activated lymphocytes.

Activated lymphocytes release numerous products which are either synthesized de novo or in increased amounts; some of these products play a role in the regulation of the immune response and are designated as mediators of cellular immune reactions or lymphokines. The first lymphokine described was the macrophage migration inhibitory factor (MIF) which has been studied most extensively with regard to its chemical and biological properties. Using sensitive radiolabelling techniques and an antiserum against highly purified fractions of MIF we were able to identify several products of activated guinea pig lymphocytes with different molecular weights of 15.000, 30.000, 45.000, 60.000 which all had an isoelectric point of 5.2 and were all inhibitory to macrophage migration. It is suggested, that these molecules are oligomers of a common subunit of molecular weight 15.000. It was further shown, that molecules of the same physical-chemical and serological characteristics are produced by activated B-cells, L2C leukemia cells and growing fibroblasts, thus further substantiating earlier reports on the production of MIF by lymphoid and non-lymphoid cells. The described molecules were also shown not to contain determinants of the major histocompatibility complex and to be distinct from lymphotoxin, another lymphocyte activation product. It is concluded, that MIF is not a single molecule but rather a system of structurally related molecules. Their interaction with macrophages and possible relationships to macrophage activating factor is discussed.

Animals↗
PubMed1978

Immune interferon. II. Different cellular site for the production of murine macrophage migration inhibitory factor and interferon.

The production of macrophage migration inhibitory factor (MIF) and immune interferon (IF) by concanavalin A (Con A)-stimulated cultures of thymus, lymph node and spleen cells was investigated. It was found that all cultures produced MIF activity, whereas only spleen cells produced marked IF activity. The capacity to produce IF was found to be correlated with the macrophage content of a cell preparation as evidenced by staining for esterase-positive cells. Furthermore, column-purified spleen T cells produced MIF but no IF. Migration inhibition caused by residual mitogen could be ruled out. On the other hand, when macrophages grown from bone marrow cells were pre-exposed to supernatants of mitogen-stimulated lymphocytes, IF activity was released into freshly added medium while no significant MIF activity was found. IF was also found in supernatants of macrophage cultures after exposure to conventional inducers in vitro (polyinosinic-polycytidylic acid, Corynebacterium parvum) or in vivo (C. parvum), whereas no MIF was detected. An anti-Type I IF serum neutralized IF in supernatants from Con A-stimulated spleen cells but did not affect MIF in the same supernatants. This indicates that IF and MIF activity are associated with different molecules. It is, therefore, concluded that under the described conditions, IF and MIF are produced by different cells. T cells are the prime producers of MIF while IF is released by macrophages following induction by lymphokines.

Animals↗
PubMed1978

Use of a radioactive double labeling technique in the chemical analysis of the mediators of cellular immunity.

Radioactive double labeling was adapted for the analysis of mediators of cellular immunity. Two identical lymphocyte cultures were simultaneously labeled with [3H]- or [14C]leucine. Each of the cultures was stimulated with antigen or mitogen. The combined supernatants were then subjected to various fractionation procedures. By determining the isotope ratio in each fraction it is possible to identify those products of activated lymphocytes that have been produced either de novo or in increased amounts. The method proved sensitive enough to detect lymphocyte activation products in supernatants of activated lymphocyte cultures from guinea pig, mouse, and man.

Animals↗
PubMed1978

Antibodies to guinea pig lymphokines. VII. Reactivity with products of lymphoid and nonlymphoid cells.

It was shown previously, that an antiserum directed against highly purified fractions of migration inhibitory factor inhibits delayed hypersensitivity reactions in vivo and in vitro. Using radiolabeling techniques we determined that the anti-lymphokine serum reacted primarily with three lymphocyte activation products (m.w. 60,000, 45,000, and 30,000) all of which had a similar isoelectric point of 5.2. The cellular origin of this material was investigated. It was found that activated B cells, B leukemia cells (L2C), and growing fibroblasts produced material of a similar m.w. as analyzed on SDS-PAGE. No cross-reaction was found with radiolabeled products of activated murine and human lymph node cells and of SV 40-infected African green monkey kidney cells. The isoelectric point of the reactive material from B cells, leukemia cells, and fibroblasts was determined at 5.2. In addition to material with pI 5.2, lymph node cells also produced material with pI 3.5 to 4.5, which focused at pH 5.0 to 5.4. After neuraminidase treatment macrophage migration inhibitory activity in fibroblast culture supernatants could be absorbed specifically to insolubilized anti-lymphokine antibody. These findings suggests that lymphoid and nonlymphoid cells are capable of producing molecules whose physicochemical and functional properties appear to be identical.

Animals↗
PubMed1977

Membrane associated antigens of human malignant melanoma. III. Specificity of human sera reacting with cultured melanoma cells.

Sera from melanoma patients, healthy donors, pregnant women and patients with types of tumors other than melanoma were tested on various melanoma lines as well as on a cultured brain tumor and adult skin fibroblasts, using a microimmune adherence test. Positive reactions against all cell lines were found in serum from each group of donors. The degree of reactivity was dependent on the cell line used. Sequential absorption with AB Rh+ and pooled platelets of more than 200 donors either reduced the titer of sera or rendered a great part of the sera negative, demonstrating that antibodies against HL-A antigens and other tissue antigens were involved. The remaining positive sera were further absorbed with pooled cells from 6- to 8-week-old fetuses. This step abolished the reactivity of most sera, indicating the relatively high frequency of antibodies in males and females against fetal antigens expressed also on melanoma and other cells. In order to determine the specificity of the few remaining positive sera, absorptions with three different melanoma cell lines, a brain tumor and fibroblasts were carried out. The results showed only partial cross-reactivity between different cell lines. No evidence was obtained from this study for the existence of a common cross-reacting membrane-associated antigen on human malignant melanoma. Antigens that could be readily detected seemed mostly to be tumor-associated fetal antigens.

Antibodies, Neoplasm↗
PubMed1977

Lymphokine-induced secretion of plasminogen activator by murine macrophages.

Thioglycollate-stimulated macrophages are known to release a plasminogen activator (PA) into the medium. In this study it was investigated whether macrophages could be activated to release PA after exposure to lymphokines. Macrophage monolayers obtained by 24 h culture of proteose peptone-elicited murine exudate cells were incubated with lymphocyte culture supernatants. After 48 h the supernatants were replaced by serum-free medium and the macrophages were incubated for another 24-48 h. These supernatants were assayed for PA as measured by the lysis of 125I-labeled fibrin. The following results were obtained: (a) Supernatants of antigen or mitogen-stimulated spleen cells induced PA secretion by macrophages whereas control supernatants were ineffective. The same was found with supernatants of mitogen-stimulated lymph node cells. (b) PA secretion by macrophages seems to be induced by a rather narrow concentration range of lymphokines. (c) Lymphokine-induced PA secretion by macrophages is enhanced after phagocytosis of latex beads. The results show that PA secretion by activated macrophages can be considered as a parameter of immunoactivation.

Animals↗
PubMed1977

Specific separation of cytotoxic T lymphocytes on immunoadsorptive films.

A method for the specific separation of cytotoxic T lymphocytes (CTL) on immunoadsorptive films is described. The films were prepared by polymerizing a mixture of gelatine and polyethyleneimine with glutaraldehyde on the bottom of plastic tissue culture flasks. By using an excess of glutaraldehyde unsaturated aldehyde groups on the film surface can react with other chemical groups predominantly with aliphatic amino groups. In this study detergent solubilized H-2 antigens were conjugated covalently to the films CTL, prepared by filtering spleen cells from alloimmunized mice through nylon wool columns, were incubated on immunoadsorptive films and the adsorbed cells were quantitatively recovered by mechanical detachment. The cells were functionally intact and tested in a microcytotoxicity assay using embryonic fibroblasts as target cells. Specificity adsorbed cells were enriched in specific cytotoxic cells up to 100 fold compared to the original fraction. Depending on the cell density per film area the non-adsorbed cells could be quantitatively depleted of CTL. The immunoadsorptive films are stabile at 37 degrees C and can be reused.

Animals↗
PubMed1977

No direct activation of fluid phase C3 by lymphokines.

Supernatants of stimulated (PPD or Con A) or unstimulated guinea pig lymph node cell cultures in serum-free medium were fractionated on Sephadex G 75. The fractions were tested for C3-consuming activities in a hemolytical assay. No C3 consumption could be detected in any fraction (MW range 80,000 to 10,000). The same result was obtained by extending the fractionation range using Sephadex G 200. A lytic activity with a molecular weight of appr. 225,000 which lysed EAC 14 cells in the presence of C2, 5, 6, 7, 8, 9 was attributed to serum C3 contaminating the cultures. It was determined that C3 is not produced in significant amounts by lymphocyte cultures.

Animals↗
PubMed1976

[Immunology of malignant melanoma (author's transl)].

Melanoma cells carry membrane-bound antigens that induced both antibody production and cellular immunity. However, these antigens appear not to be tumor-specific, as the activity of human antisera can be absorbed out by fetal antigens. Nonetheless, the phenomenon of spontaneous regression, though mostly affecting only parts of a lesion, indicates that effective attack mechanisms do exist. Simultaneous tumor progression is due to heterogeneity of tumor cells, which vary widely in antigen expression. Cells that are not recognizable sneak through defense mechanisms and produce metastases.

Antigens, Neoplasm↗
PubMed1976

Antibodies to guinea pig lymphokines. III. Reactions with radiolabeled lymphocyte activation products.

An antiserum raised against a purified fraction of guinea pig lymphokines exhibits marked in vivo properties; it suppresses delayed hypersensitivity reactions and binds migration inhibition factor (MIF) from supernatants of activated lymphocyte cultures in vitro. This serum was analyzed for specificity using a radioactive double labeling technique which distinguishes products synthesized either de novo or in increased amounts by stimulated lymphocytes. Combined supernatants of stimulated (concanavalin A or PPD) and unstimulated cultures labeled with either tritiated or [14C]leucine, respectively, were fractionated on Sephadex G-75. Pooled fractions were precipitated using the antibody sandwich technique, and solubilized precipitates were analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Using this procedure the anti-lymphokine serum recognized primarily three newly sythesized lymphocyte activation products with molecular weights of approximately 60 000, 45 000 and 30 000 daltons. By contrast, these molecules could not be detected in radiolabeled lymph node cells which had been solubilized with NP-40 detergnt. The isoelectric point of all three molecules was found to be 5.2 +/- 0.3. The previously determined characteristics (mol.wt. 45 000, pI 5.2) of MIF and the property of the anti-lymphokine serum to absorb MIF activity suggest an identity between MIF and one of the molecules. In view of the previously described in vivo effects of the anti-lymphokine serum it is concluded that at least one of these three molecules plays an important role in the early events of delayed-type hypersensitive reactions in vivo.

Animals↗
PubMed1976

Membrane associated antigens of human malignant melanoma. II. Leucocyte migration studies with formalin fixed human melanoma cells.

The leucocyte migration test from caillary tubes was examined for its usefulness as an assay for cell-mediated immunity in melanoma patients. Formalin fixed melanoma cells either obtained from established cell lines or freshly excised tumors were used as antigen source. From a group of 33 melanoma patients 14 reacted positively (42%) when fixed cultured cells were used, whereas, no positive reactions were found in a group of 14 control donors. However, a considerable proportion of patients with chronic inflammatory processes of the skin reacted positively (4/17 = 24%). A smaller proportion of positive reactions were found in melanoma patients when fixed melanoma cells from excised tumors were used (1/16 = 6%). The positive results in the group with chronic inflammatory processes may be explained as reactions against melanoma associated, but not melanoma-specific, antigens. Three possible reasons are discussed for the low frequency of positive reactions with cells from excised tumors: 1. the cells used in this study display only a few of the antigenic determinants typical for malignant melanoma, 2. antigen expression is quantitatively lower. 3. the surface antigens are covered by blocking factors.

Antigens, Neoplasm↗
PubMed1975

Radioactive labelling and characterization of the products of activated mouse lymphocytes.

For chemical characterization of the products of activated lymphocytes a radioactive double-label technique was developed which allows one to distinguish those products synthesized either de novo or in increased amounts by the stimulated culture. Spleen cells from Balb/c mice were cultured in serum-free medium in the presence or absence of concanavalin A and simultaneously labelled with radioactive leucine. Optimal culture conditions were established by determining parameters such as cell density, mitogen concentration, and kinetics of protein synthesis following stimulation. Combined supernatants of stimulated and unstimulated cultures each labelled with either [3H]leucine or [14C]leucine were fractionated on Sephadex G-75. Materials derived from control or stimulated supernatants both yielded a qualitatively similar radiolabelled profile. The isotope ratio of stimulated to nonstimulated culture, however, showed a broad peak at KD 0--.35 (approx. mol. wt 75000-20000) which was further analyzed by isoelectric focusing. Pools of every two fractions were focused in polyacrylamide gels at pH 3.5-10. By determining the isotope ratio, the isoelectric point, and the KD (mol wt), it was possible to distinguish at least 24 molecules which had been produced only, or in greater degree, by the stimulated culture.

Animals↗