Search PubMed⌕ Search

Biomedical subjects

A Matter

Publications and source records attributed to A Matter.

At least 55 records · Page 3Linked to original sources
PubMed1979

Microcinematographic and electron microscopic analysis of target cell lysis induced by cytotoxic T lymphocytes.

A study was carried out to determine the sequence of events of T-cell mediated target cell lysis in microcinematography and electron microscopy. Highly efficient cytotoxic T lymphocytes (CTL) were generated in vivo and in vitro using preimmunized spleen cells and purification procedures. Such CTL were highly specific. This specificity correlated well with the number of adhesions formed between CTL and targets and this criterion was used to study killer-target cell interaction. Microcinematography showed that target cell lysis at the single cell level, despite time variations, could be clearly separated into three phases: (a) a recognition phase, visible by random crawling of CTL over the target cell surface until firm contact was established; (b) a post-recognition phase, during which firm contact between CTL and target was maintained without gross modification of either cell; (c) a phase of target cell disintegration, mainly characterized by vigorous blebbing of the cell membrane resulting in a motionless carcass of the target cell but not in its total dissolution. Only later this carcass decayed and formed a necrotic ghost. Electron microscopic observations were put into sequence according to microcinematography. Post-recognition phase was characterized by a tight apposition of the membranes of CTL and target cell. No gap junctions could be observed. During target cell disintegration, profound cytoplasmic and nuclear changes occurred simultaneous with surface blebbing. Most noticeable were extensive internal vacuolization, mitochondrial swelling, nuclear pycnosis and dissolution of the nucleolus. These observations suggested that target cell lysis does not start with a surface phenomenon similar to complement lysis, but a process involving practically the whole cell simultaneously. It is conceivable, therefore, that the signal from the CTL is transmitted across the target cell, and that the switch to sudden cell death is manipulated deep inside the cell.

Animals↗
PubMed1978

Retinoic acid-binding protein in human breast cancer and dysplasia.

Seventy-five specimens of human breast tissue were checked for the presence of cellular retinoic acid-binding protein (cRABP). Fifty-two percent of the primary carcinomas and 43% of the dysplastic breast lesions (stage MII) contained detectable amounts of crabp, whereas no cRABP was found in normal tissue. Sucrose gradient centrifugation and electrophoresis on agarose were used for analysis of the presence of cRABP. The cRABP of human origin (normal uterus and neoplastic mammary tissue) differed in its mobility in agarose electrophoresis from that of rat testis cRABP.

Animals↗
PubMed1976

The differentiation of cytotoxic T lymphocytes in vitro: an ultrastructural study.

T killer cells were identified morphologically in two different culture systems. The first system allowed identification by comparing under identical culture conditions two types of stimulation, one leading to cytotoxic activity levels that were very high (H-2 stimulation) and the other to levels which were practically nil (M-locus stimulation). A second system allowed identification by the use of a collaborative system in which relatively pure precursors of T killer cells were mixed with precursors of T amplifier cells from which they were distinguishable by their Thy-l antigen. In this latter case, surface labelling techniques had to be used. As in the in vivo situation, T killer cells were medium-sized pale cells with evidence of a well-developed secretory and motile apparatus. No evidence of highly active protein synthesis was found. Other T cells were dark and mainly derived from the T amplifier population, again consistent with in vivo findings. There was considerable background proliferation, even in the absence of any added antigen, and this included the formation of some well-developed plasma cells.

Animals↗
PubMed1976

Culture conditions for induction of suppressor cells in vitro.

Culture conditions have been established for optimal generation of cytotoxic T lymphocytes (CTL) in one-way mixed lymphocyte cultures (MLC). The responder cell concentration was found to be most critical. In general the more active the proliferation was, the lower was the optimum for CTL generation. Optimal proliferation was usually found to occur at lower cell concentrations than optimal CTL generation. Above the optimal CTL generation proliferation also decreased, most likely due to overcrowding. These observations were made on both unpurified and nylon wool-passaged spleen cells, though the latter generally produced higher levels of cytotoxic activity per equal number of harvested cells. Cells prestimulated for 2 or 4 days in the absence or presence of antigen (M-locus differences) were unable to mount an effective response when restimulated with another antigen presenting an H-2 difference. This hyporesponsiveness was not due to the exhaustion of the culture medium or the presence of dead cells (since these were removed before restimulation). A high degree of hyporesponsiveness was also induced in the absence of antigen during prestimulation which rendered antigenic competition highly unlikely. Overcrowding could be excluded since the observed inhibition could not be diluted out by lowering the responder cell concentrations. A carry-over of CTL destroying newly added antigen (Fitch et al., 1975) could not account for our observations since in the system utilized (M-locus stimulation) there was no generation of CTL (Festerstein, 1973; Röllinghoff et al., 1975). The development of suppressor cells would seem the most likley explanation of the data.

Animals↗
PubMed1976

Protection against murine ascites tumours by lymphoid cell populations with T memory or cytotoxicity.

It was possible to protect irradiated C3H mice against lethal doses of allogeneic ascitic tumor cells (RBL-3 or P-815 Y) by systemic administration of low doses of syngeneic sensitized lymphoid cells. Two types of cell populations were active at similar doses: (1) spleen cells harvested 2 months after a nonlethal inoculation of tumour cells, at which time no cytotoxic lymphocytes wer in vivo sensitization or in vitro sensitized spleen cells; sucll and dose dependent and target cell specific. The findings imply that T memory cells as well as cytotoxic cells are able to protect, although it was not possible to exclude the presence of memory lymphocytes in the cytotoxic cell population. Antiserum to cytotoxic T cells (CTL) was prepared in an attempt to distinguish memory and cytotoxic effector cells. The antiserum did not react with the majority of T cells in a normal spleen or thymus, but showed specificity for the CTL cell lineage. Antiserum treatment and complement abolished protection in all types of sensitized cell populations. Since memory and cytotoxic cells appeared to share differentiation antigens, we could not establish whether memory cells are precursors or products of cytotoxic cells.

Animals↗
PubMed1975

Morphological definition of thymocyte subpopulations.

An attempt was made to distinguish immature from mature, immunocompetent thymocytes in the adult mouse using morphological criteria. All procedures enriching for competent thymocytes also enrich small cells whose morphology is very similar to the small thymocytes that have been described in the medulla of the thymus (Abe and Ito, 1970). A heterogeneity of competent thymocytes is likely since the enriched populations always contain a number of medium sized cells. These latter cells show spontaneous DNA-synthetic activity and are probably the source of thymus proliferative activity. Owing to their characteristic morphology these two cell types might represent the precursors for each of the two differentiated T cell types that have been found to occur in delayed type hypersensitivity (Matter, 1974).

Animals↗
PubMed1975

A study of proteolysis as a possible mechanism for T-cell-mediated target cell lysis.

The hypothesis that proteolysis is implicated in T-cell-mediated target cell lysis was tested in two ways: first, various inhibitors of protease activity were used either during or before the cytotoxicity test. Ovomucoid, TPCK, and PMSF proved to be not or only marginally inhibitory, whereas the considerable inhibitory action of TLCK was shown to most likely be a toxic effect of the inhibitor. Second, radioactive substrates for cathepsin activity were used, either free in the medium or fixed on the surface of the target cells, to detect a possible breakdown of these substrates by a release of intracellular cathepsins during the cytotoxicity test. Very little dialysable breakdown products were formed, and there was no difference between their amount in either a homologus or a heterologous system. It is concluded that proteolysis probably is not the mechanism by which target cells are killed. Alternative mechanisms are discussed.

Animals↗
PubMed1974

The differentiation pathway of T lymphocytes. Evidence for two differentiated cell types.

Two experimental models have been used to study T-cell differentiation. The first, a graft-vs.-host reaction, was induced by injecting thymocytes or cortisone-resistant thymocytes into lethally irradiated allogeneic mice. The second was tumor graft rejection in allogeneic hosts. Ultrastructural studies at various time intervals revealed two differentiated T-cell types. One of these (the "pale" cell) is probably high cytotoxic as measured in the chromium-release assay, the other (the "dark" cell) may be an "amplifier" cell, helping in the differentiation of cytotoxic cells.

Animals↗
PubMed1973

A morphometric study on the nexus of rat cardiac muscle.

A morphometric study of the nexus of rat cardiac muscle was carried out. The nexus surface of one intercalated disk of one 15 microm thick fiber is found to range between 47 microm(2) and 94 microm(2), the latter value taking into account the maximal underestimation caused by tangential sectioning. Dividing the lower, minimal value by the surface of the observed subunits (90 A periodicity), one obtains for one intercalated disk 6.7 x 10(5) subunits, each of them assumed to be permeated by a central pore. These pores are thought to be equivalent to intercellular channels in a recently proposed model. Taking our morphometric and recently reported physiological values, this model is examined for its consistency with a low resistance pathway between cardiac muscle cells.

Animals↗
PubMed1972

Mouse thymus-independent and thymus-derived lymphoid cells. II. Ultrastructural studies.

The ultrastructural features of B-, T-, and surface Ig(sIg)-bearing cells have been studied on cell suspensions from lymphoid organs of mice at different stages of immunization. The cells were identified by exposure to rabbit antibodies against mouse-specific lymphocyte antigens (MSLA) or brain-associated theta antigen (BAtheta) for T cells, mouse-specific bone marrow-derived lymphocyte antigens (MBLA) for B cells, and mouse Ig for sIg-bearing cells. The rabbit antibodies fixed on the cell surfaces were detected by peroxidase-labeled sheep anti-rabbit Ig antibodies or by a "bridge" technique using southern bean mosaic virus or bacteriophage T4 as the final markers. In some experiments, short-lived lymphoid cells were labeled in vivo with repeated tritiated thymidine and the ultrastructural detection of their surface antigens was combined with radioautography. MBLA+ lymphoid cells showed a whole range of ultrastructural patterns. Most were small and medium-sized lymphocytes with a clear cytoplasm containing mono- and polyribosomes, but they comprised also blasts and large cells with various amounts of endoplasmic reticulum, as well as plasma cells at different stages of maturation. sIg-bearing cells appeared to be identical with MBLA+ cells, except that sIg was less easily detectable on large blasts, and only very rarely observed on plasma cells. MSLA+ and BAtheta+ cells fell into three categories. One of them (T(1) cells) consisted of small to medium-sized lymphocytes with a clear cytoplasm and few organelles, mostly monoribosomes. A second consisted of large cells (T(2) cells) characterized by numerous polyribosomes often in a "rosette"-like pattern, occasional dark, membrane-bound granules, and a developing "filamentous network." The third, very characteristic type, (T(3) cells) was represented by dark small to medium-sized lymphocytes, usually containing large amounts of closely packed ribosomes and showing a striking accumulation of filamentous network, often condensed in large areas devoid of cell organelles. This filamentous network appeared to correspond to the cytochalasin B-sensitive system of microfilaments found in other cells and considered to be one of the contractile elements of the cell. The T(3) lymphocytes showed frequently vesicles suggestive of a strong pinocytic activity, and assumed a variety of shapes, including uropods. Evidence is presented that T(1) lymphocytes represent "virgin" T cells, T(2) "activated," and T(3) "differentiated" lymphocytes.

Animals↗
PubMed1972

Mouse thymus-independent and thymus-derived lymphoid cells. I. Immunofluorescent and functional studies.

The simultaneous use on mouse lymphoid suspensions of heterologous antisera directed against thymus-derived (T) cell mouse-specific lymphocyte antigen and brain-associated theta antigen (MSLA and BAtheta) or thymus-independent (B) cell mouse-specific bone marrow-derived lymphocyte antigen (MBLA) surface antigens allowed direct proof of the different specificity of these antisera by double immunofluorescence (IF) staining with selective visualization of fluorochromes. These antisera and antisera against mouse Ig and its different types of chains were then used with technique of either double IF staining or IF combined with radioautography, allowing the following conclusions: (a) Surface Ig (sIg) was found exclusively on B cells and never on T cells, but not all B cells had sIg. Cells containing detectable amounts of Ig were MBLA+, but had less sIg than other B cells or none at all. There was evidence for the existence of a significant number of MBLA+ lymphocytes, neither bearing nor containing detectable Ig. (b) micro-Chains were the most frequent but not the only heavy chains found on spleen cells; however, it could not be decided with the technique used, if a single cell can bear more than one type of heavy chain. No cell containing gamma-chains was found to bear surface micro-chains, although a very few cells containing both micro- and gamma-chains were observed. (c) The antigen-binding cells detected after immunization with bacteriophage T4, bovine serum albumin, Maia squinado hemocyanin, and sheep erythrocytes were analyzed for MSLA, MBLA or sIg using double IF, a combination of IF and radioautography, or inhibition of "rosette" formation. Practically all the antigen-binding cells detected were MSLA-, MBLA+, sIg+. (d) More B cells than T cells were found among short-lived lymphoid cells labeled by repeated in vivo injections of tritiated thymidine, but the results did not support a simplified concept equating T cells to long-lived and B cells to short-lived lymphocytes. (e) Cells dividing rapidly in the lymph nodes draining the sites of immunization with various antigens were predominantly T cells 2 days after immunization and in majority B cells a few days later. (f) Incubation of lymphoid cells at 37 degrees C with rabbit anti-mouse Ig or anti-kappa chains led to complete disappearance of sIg and to decrease of MBLA ("antigenic modulation"). In the same conditions, anti-MBLA gave partial modulation of MBLA and of sIg; MBLA, however, reappeared much faster than sIg. No modulation of T cell surface antigens by the appropriate antisera was observed. Cell treatment with Pronase could remove MBLA, sIg, MSLA, and BAtheta, which reappeared within a few hours. Neuraminidase treatment was without detectable effect on these antigens.

Animals↗