QUANTITATIVE STUDIES ON THE BEHAVIOR OF SENSITIZED LYMPHOCYTES IN VITRO : I. RELATIONSHIP OF THE DEGREE OF DESTRUCTION OF HOMOLOGOUS TARGET CELLS TO THE NUMBER OF LYMPHOCYTES AND TO THE TIME OF CONTACT IN CULTURE AND CONSIDERATION OF THE EFFECTS OF ISOIMMUNE SERUM

How immunoglobulin G antibodies kill target cells: revisiting an old paradigm

The capacity of immunoglobulin G (IgG) antibodies to eliminate virtually any target cell has resulted in the widespread introduction of cytotoxic antibodies into the clinic in settings of cancer therapy, autoimmunity, and transplantation, for example. More recently, it has become apparent that also the protection from viral infection via IgG antibodies may require cytotoxic effector functions, suggesting that antibody-dependent cellular cytotoxicity (ADCC) directed against malignant or virally infected cells is one of the most essential effector mechanisms triggered by IgG antibodies to protect the host. A detailed understanding of the underlying molecular and cellular pathways is critical, therefore, to make full use of this antibody effector function. Several studies over the last years have provided novel insights into the effector pathways and innate immune effector cells responsible for ADCC reactions. One of the most notable outcomes of many of these reports is that cells of the mononuclear phagocytic system rather than natural killer cells are critical for removal of IgG opsonized target cells in vivo.

iNOS-mediated secondary inflammatory response differs between rat strains following experimental brain contusion

BACKGROUND

Nitric oxide is a key mediator of post-traumatic inflammation in the brain. We examined the expressions of iNOS, nNOS, and eNOS in inbred DA and PVGa rat strains where DA is susceptible to autoimmune neuroinflammation and PVGa-resistant.

METHODS

Parietal contusions using a weight drop model were produced in five rats per genotype. After 24 h, the brains were removed and analyzed using a range of immunohistochemical methods.

RESULTS

PVGa presented significantly increased iNOS expression in infiltrating inflammatory cells in the perilesional area compared to DA (p < 0.05). The amount of w3/13-positive infiltrating inflammatory cells did not differ between strains. eNOS and nNOS expression did not differ between strains. iNOS-positive cells coexpressed neuronal (NeuN), macrophage (ED-1), and leucocyte (w3/13) markers. MnSOD was significantly increased in PVGa (p < 0.05). 3-Nitrotyrosine, a measure of peroxynitrite levels, and fluoro-jade stained neuronal degeneration, did not differ between strains.

CONCLUSIONS

Two inbred rat strains with genetically determined differences in susceptibility to develop autoimmune disease displayed different levels of the inflammatory and anti-inflammatory mediators iNOS and MnSOD, indicating genetic regulation. Interestingly, the increased levels of iNOS did not lead to elevated expression of the neuronal cell-death marker fluoro-jade. The increased iNOS expression was correlated with increased expression of superoxide scavenger MnSOD. Excessive peroxynitrite formation was probably prevented by limitation of available superoxide. Subsequently, the higher expression of potentially deleterious iNOS in PVGa did not result in increased neuronal death.

Cardiac adenosine production in rat genetic models of low and high exercise capacity

We previously demonstrated that Copenhagen (COP) and DA inbred rat strains show a wide difference in a test for aerobic treadmill running that correlated positively with isolated cardiac function. The purpose of this study was to test adenosine production as a candidate intermediate phenotype that may explain part of the difference in running and cardiac performance in these genetic models for low and high aerobic capacity. Adenosine production was measured as the activity of soluble 5'-nucleotidase and membrane-bound ecto-5'-nucleotidase in the membrane pellet and supernatant fractions of left and right ventricular muscle and gracilis muscle taken from 10 DA and 10 COP rats. Ecto-5'-nucleotidase activity in the membrane pellet of hearts from both DA and COP accounted for the vast majority of the total tissue adenosine production (>90% in the left ventricle and >80% in the right ventricle). Ecto-5'-nucleotidase activity in the pellet fraction was significantly higher in the left (22.4%) and right (46.1%) ventricles of DA rats compared with COP rats, with no differences in total protein content. There were no significant differences between the strains for 5'-nucleotidase activity in the cardiac supernatant, the gracilis pellet, or the gracilis supernatant. These data support the hypothesis that an increase in cardiac adenosine production may contribute to the greater aerobic running capacity of the DA rats.

A genome scan for Loci associated with aerobic running capacity in rats

Aerobic capacity is a complex trait that defines the efficiency to use atmospheric oxygen as an electron acceptor in energy transfer. Copenhagen (COP) and DA inbred rat strains show a wide difference in a test for aerobic treadmill running and serve as contrasting genetic models for aerobic capacity. A genome scan was carried out on an F(2)(COP x DA) segregating population (n=224) to detect quantitative trait loci (QTLs) associated with aerobic running capacity. Linkage analysis revealed a significant QTL on chromosome 16 (lod score, 4.0). A suggestive linkage was found near the p-terminus of chromosome 3 (lod score, 2.2) with evidence of an interaction with another QTL on chromosome 16 (lod score, 2.9). All three QTLs showed a dominant mode of inheritance in which the presence of at least one DA allele was associated with a greater distance run. These results represent the first aerobic capacity QTLs identified in genetic models.

Cardiac performance in inbred rat genetic models of low and high running capacity

1. Previous work demonstrating that DA inbred rats are superior to COP inbred rats in aerobic treadmill running capacity has indicated their utility as genetic models to explore this trait. We tested the general hypothesis that intermediate phenotypes of cardiac function and calcium metabolism are responsible for the difference in capacity between these strains. 2. Logical cardiac trait differences were estimated at a tissue (isolated papillary muscle), cellular (isolated left ventricular cells), and biochemical level of organization. 3. DA hearts were found to give significantly higher values than COP hearts for: (1) maximal developed tension (38.3 % greater), and rates of tension change in contraction (61 %) or relaxation (59 %) of isolated papillary muscle, (2) fractional shortening (50 %), amplitude of the Ca(2+) transient (78.6 %), and caffeine-induced release of Ca(2+) from the sarcoplasmic reticulum (SR; 260 %) in isolated ventricular myocytes, and (3) Na(+),K(+)-ATPase activity of isolated myocytes (17.3 %). 4. Our results suggest that these trait differences may prove useful for further studies into the genes responsible for natural variations in both ventricular function and aerobic endurance capacity. Understanding the genetic basis of aerobic capacity will help define the continuum between health and disease.

QUANTITATIVE STUDIES ON THE BEHAVIOR OF SENSITIZED LYMPHOCYTES IN VITRO. II. INHIBITORY INFLUENCE OF THE IMMUNE SUPPRESSOR, IMURAN, ON THE DESTRUCTIVE REACTION OF SENSITIZED LYMPHOID CELLS AGAINST HOMOLOGOUS TARGET CELLS

The cytocidal effect of specifically sensitized lymphoid cells on homologous target cells in culture can be inhibited by small quantities of an imidazole derivative of 6-mercaptopurine (imuran). This inhibition takes place only in the continuous presence of this drug, and at concentrations which apparently do not affect the viability of the attacking lymphoid cells. These results seem to support the contention that RNA-dependent protein synthesis on the part of the lymphoid cells is necessary for a destructive interaction between sensitized node cells and homologous target cells in vitro.

Cell-mediated cytotoxicity. A highly sensitive and informative flow cytometric assay

Determination of target cell lysis by cytolytic effectors has typically been achieved by two methods: the release of various markers from the cell, as in 51chromium release assays and the uptake of markers into the cell, as in trypan blue uptake in single cell/conjugate binding assays. Problems associated with these assays might include: (1) poor uptake, (2) nonspecific release, (3) poor statistics, (4) length of assays, or (5) subjectivity. These difficulties prompted the development of a new sensitive flow cytometric assay employing two fluorochromes. PKH-1, a fluorochrome which fluoresces in the green, binds to the cytoplasmic membrane and does not leak or transfer, is used to identify the target cell population. Propidium iodide fluoresces in the red and is used to detect non-viable cells. Use of these two fluorochromes and two parameter analysis allows for identification of four subpopulations in the sample: live effectors, dead effectors, live targets and dead targets. By enumeration of these subpopulations the following information can be calculated: (1) the percent target lysis, (2) effector-to-target cell ratios, (3) viability of the effector cells at the termination of the assay, and (4) viable effector to target cell ratios. The results show that PKH-1 labeling of target cells had no effect on effector-target cell interactions. Excellent correlation was found between this method and the chromium assay, however, due to earlier detection of the lytic event, this method provides a distinct time advantage over current methods.

An animal model to investigate the interaction between the immune system and oral carcinomas

In an attempt to investigate the role of the immune system in oral squamous cell carcinoma, an animal model was developed with an inbred strain of mice. Well-differentiated oral squamous cell carcinomas were induced with a polycyclic hydrocarbon in immunogenetically identical mice. The oral tumors that developed were maintained in vivo. Once established, the tumors were adapted to tissue culture and the resulting cell lines were cloned. An immunization protocol was formulated to detect the generation of cytolytic effector cells by using a microcytotoxic chromium-51 release assay to assess the immune response of the host.

A sensitive method to measure PHA-induced cytotoxicity to adherent target cells using [3H]uridine as a terminal label

This paper describes a modification of the PHA-induced cytotoxicity test of human peripheral blood lymphocytes against a tumour-derived adherent cell line (HeLa), in which the surviving target cells are labelled with [3H]uridine at the end of the assay. There is a direct correlation between [3H]uridine incorporation and the number of adherent target cells. The test proves to be very sensitive at low effector; target cell ratios. Frozen stored cells can be used in this system, a particular advantage because of the possibility of increasing the reproducibility of the assay by using the same batch of cryopreserved lymphocytes as a reference standard in each experiment. PHA-induced cytotoxicity was mainly found in the T cell enriched fraction.

Environmental chemical-induced modification of cell-mediated immune responses

It is therefore proposed that: 1) environmental chemicals can have specific mechanisms of toxicity and can influence antibody-mediated immunity while having no detectable effect on cell-mediated immunity, 2) immune dysfunction is related to exposure time to a chemical and the tissue concentration of that chemical, 3) recovery of immune function may occur even though chemical exposure continues, and 4) a single assay of immune function may not be appropriate to detect chemical induced immune dysfunction.

Lymphocyte cytotoxicity in the X-irradiation induced rat small bowel adenocarcinoma. II. Presence of cytotoxic lymphocytes in irradiated animals

Cytotoxic peripheral blood lymphoid cells were demonstrated in both Holtzman and Lewis Brown-Norway rats which had received 2000R of local X-irradiation to the temporarily hypoxic, exteriorized, ileum and jejunum regardless of whether a small bowel adenocarcinoma subsequently developed. The cytotoxic response, which was detectable at two days, was quite evident by day 5 post-irradiation. No evidence of cross-reacting tumor antigens was obtained when similarly processed effector cells from Holtzman rats bearing a spontaneous mammary carcinoma were incubated with cell cultures derived from the small bowel adenocarcinoma. These findings indicate X-irradiation of the small bowel initiates lymphocyte sensitization that is manifested as in vitro cytotoxicity against cell cultures of the adenocarcinoma.

Selective platelet immune retention

Inbred rats were immunized with Freund's Adjuvant containing proteins of Mycogacterium tuberculosis, Mycobacterium butyrium, or dinitrochlorobenzene (DNCB). Native arterial blood was then passed over glass beads coated with those antigens. The platelet retention on the glass beads was measured. Rats immunized with Complete Freund's Adjuvant developed accelerated platelet retention on beads coated with protein derivatives of tuberculosis (PPD) after just 18 seconds of blood flow. Rats immunized twice maintained selective retention longer than those immunized once. The test animals developed no cutaneous hypersensitivity nor precipitin lines on Ouchterlong gels against PPD. Rats sensitized to DNCB had accelerated platelet retention on DNCB-coated beads. Results were temperature and complement dependent, and antigen-specific. Heparin caused a dose-dependent inhibition of the accelerated retention. PPD potentiated the ADP-induced aggregation of plateletrich plasma (PRP) from immunized rats. These experiments suggest that platelets react selectively to antigens in the intravascular spaces in immune reactions.

Cellular requirements for the induction of cytotoxic T cells in vitro

The stimulator and accessory cell requirements for the induction of cytotoxic T cell responses to alloantigens in vitro are reviewed. The ability of lymphocytes to stimulate was acquired early in development and was found to be a property of both Ig+ and Ig- cells. The presence of Fc receptors, complement receptors or Ia antigens on lymphocytes did not confer superior stimulator capacity. In contrast to lymphocytes mature macrophages were poor stimulators. When resting lymphocytes were used as a source of stimulator cells there was an additional requirement for an adherent accessory cell population for the induction of cytotoxic T cells. The accessory cell population functioned whether syngeneic or allogeneic with the responder and was required for the induction rather than the maintenance of the response. It was further characterized as an Ig+, theta, FcR+/-, CR +/-, Ia- cell which was not a mature macrophage. Accessory cells could be replaced to some extent by supernatants from spleen cell cultures. A model for T cell induction is proposed where only cells which produce unique inductive stimuli are able to function as stimulator cells. Stimulator cells are defined as those cells capable of stimulating cytotoxic T cell precursors directly and independently. Stimulator capacity is suggested to be a function of activated cells only, thus lymphocytes only stimulate following activation by accessory cells. Cells lacking innate stimulator capacity but exhibiting Ia antigens are suggested to stimulate via an alternative means.

Rosetting and other reactions of the Reed-Sternberg cell

Clustering of lymphocytes around Reed-Sternberg cells was noticed in single cell suspensions made from viable Hodgkin's lymphoid tissue. Cytocentrifugation of the suspension showed that clustering also occurred around a smaller cell type, thought to be the precursor of the classical Reed-Sternberg cell. Time-lapse cine films taken of the clustering showed unceasing activity on the part of the lymphocytes migrating over the surface of the central cell. Reed-Sternberg cells were reacted with anti-monocyte serum using indirect fluorescence techniques. In its mature form at least, the Reed-Sternberg cell showed no activity with the antiserum. No immunoglobulin was detected in the Reed-Sternberg cell using fluorescence techniques, but a few Reed-Sternberg cells showed diffuse cytoplasmic staining using the peroxidase-labelled antibody technique. Membrane receptor tests showed the lymphocytes surrounding the Reed-Sternberg cell to be T-cells. After proteolytic enzyme treatment to free lymphocytes from the surface, the Reed-Sternberg cell bound IgG-coated red blood cells indicating a probable Fc receptor. Cytochemistry demonstrated weak non-specific esterase activity in a small minority of Reed-Sternberg cells, and absence of acid phosphatase, alkaline phosphatase and peroxidase. A subpopulation of lymphocytes with distinctive segmentation of the nucleus was noted. These were often to be seen participating in lymphocyte rosettes around the Reed-Sternberg cell.

Histocompatibility antigen-activated cytotoxic T lymphocytes. I. Estimates of the absolute frequency of killer cells generated in vitro

A sensitive procedure employing limiting dilution of activated lymphocytes and 51Cr release from highly labeled target cells was used to derive minimal estimates of the absolute frequency of cytotoxic T lymphocytes (CTL) present in a population of mouse lymphocytes activated to alloantigens of the major histocompatibility complex in bulk mixed lymphocyte cultures. From this figure (0.7-1.2%), the maximal rate of target cell killing could be calculated to be approximately 4 targets/CTL/hour.

H-2 antigen-specific cytotoxic T cells induced by concanavalin A: estimation of their relative frequency

Specific and nonspecific lysis of DBA/2 (H-2d) mastocytoma cells, P815, by concanavalin A (Con A)-induced cytotoxic T cells was studied. In the assay for nonspecific lysis, phytohemagglutinin (PHA) was present to glue the target and killer cells together. We have presented evidence previously to show that PHA reveals only, and all, cytotoxic T cells. In the assay for specific lysis the only glue present was specific receptors on a fraction of the killer cells and surface antigens of P815. We show that when PHA was present, Con A-induced cells which were syngeneic, semi-syngeneic, or allogeneic, lysed P815 very efficiently in a 4-h 51Cr release assay. However, only Con A-induced T cells which were allogeneic and did not carry H-2d lysed P815 when the assay was carried out in the absence of PHA. In an experiment with two target cells, Con A-induced B10 (H-2b) T cells lysed B10.D2 (H-2d) targets specifically but did not lyse B10 targets, while Con A-induced B10.D2 T cells lysed B10 targets specifically but not B10.D2 targets. Furthermore, Con A-induced B6 (H-2b) T cells from normal mice lysed P815 specifically but Con A-induced B6 T cells from irradiated F1 (B6 x BALB/c) (H-2b/d) mice reconstituted with B6 bone marrow did not lyse P815 specifically. A fraction of Con A-induced T cells therefore appear to bear specific surface receptors for nonself H-2 coded structures. We describe conditions of assay and a new method of plotting the results such that nonspecific (PHA-revealed) and specific (PHA-independent) cytotoxicity can be quantitatively compared. We conclude that 1-4% of the total Con A-induced cytotoxic effector T cells are directed against any particular foreign H-2 haplotype. This is the first estimate of the relative frequency of antigen-reactive cytotoxic T cells.

Immunologic and chemical studies on mucopolysaccharide derived from murine lymphosarcoma

Mucopolysaccharide was prepared from media in which the Gardner's lymphosarcoma cells were cultured. Multiple intraperitoneal injections of the preparation into syngeneic mice resulted in enhancement of the tumors which were inoculated prior to the injections. Sera of these hosts contained antibodies reacting with antigens of the outer layer of the tumor cells. Chemical analyses of the preparation showed that the mucopolysaccharide is composed of hexosamine, uronic, acid, hexose, and proteins. The mucopolysaccharide was shown to possess unique migration rate on electrophoresis and thin layer chromatography.

T-lymphocyte receptors for alloantigens

Recent developments in research on T-cell receptors for alloantigens have been reviewed. Recognition of these antigens is T-cell dependent and, when measured in the PAR test, can be shown to take place with receptors present on T cells, with those shed spontaneously from T cells and also with "recognition structures" of as yet unknown origin and structure present in post-transplantation alloantiserum but absent from B-cell induce alloantiserum. All recognizing structures of parent T-cell origin mentioned above also induce formation of anti-T cell receptor antisera when injected into appropriate F1 hybrid animals. The highly specific inhibitory activity of the sera can be demonstrated both in vitro and in vivo, and the most fascinating aspect constitutes cytotoxic elimination of T cells bearing receptors for a given alloantigenic specificity without harming T cells with other alloreceptors. The biochemical nature of T-cell receptors is not known and, depending on the physical form in which it is investigated, high molecular weight as well as considerably lower molecular weight structures have been found. It has, on the other hand, become quite clear that the antigen-binding region of B- and T-cell receptors shows idiotypic similarity and it is, therefore, likely that this part of the receptor molecule of both lymphocyte classes is similar if not identical

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.

Electron microscopy of lymphocytes and hepatocytes in orthotopic liver homografts during the late rejection (target cell destruction by lymphocytes in vivo?)

The results of electron microscopical observations made on orthotopic procine liver homografts during the process of delayed rejection show close contacts between the cell membranes of lymphocytes and hepatocytes, the lymphocytes reaching the hepatocytes by incomplete and complete migration through the partially enlarged intracellular and intercellular gaps of the endothelial sinusoid lining. In addition, the lymphocytes are capable of coming into contact with the surfaces of hepatocytes through both intercellular and intracellular endothelial gaps by means of microvilli form and uropodlike cytoplasmic projections. The hepatocytes exhibit partly direct, partly indirect signs of a localized change of the cell membrane which is associated with abnormal permeability, partial peripheral lysis and colliquation necroses. Such alterations were frequently found to be located in the immediate neighborhood of both lymphocytes and lymphoid cells. The interpretation of these electron microscopical findings as being an expression of in vivo target cell destruction by lymphocytes is discussed.

Leukocyte mediated cytotoxicity of chemically induced rat salivary gland neoplasms

Chemically induced tumors of the rat submaxillary glands were tested for the presence of tumor antigens by in vitro leukocyte mediated cytotoxicity assays. Since it has been reported that the saliva of humans with oral cancer contains markedly elevated levels of secretory antibody, the rats' saliva specimens were also tested for blocking and/or potentiating "antibody" activity. The results indicate that saliva from tumor-bearing animals potentiated tumor cell killing if either the tumor cells or leukocytes were pretreated. The effect was much more marked when tumor cells were pretreated. Furthermore, the addition of saliva to tumor cells imparted an immunologic cross reactivity which was not present with untreated tumor cells. Control saliva occasionally produced a similar effect, but not as consistently or with the potency of saliva from tumor-bearing animals. Heat inactivation did not abrogate this potentiation. It is inferred that this may indicate a new system of immunologic surveillance, i.e. arming or potentiation of leukocytes by soluble tumor antigens in glandular secretions.