Publisher Summary Studies of cytotoxicity by human lymphocytes revealed not only that both allogeneic and syngeneic tumor cells were lysed in a non-MHC-restricted fashion, but also that lymphocytes from normal donors were often cytotoxic. Lymphocytes from any healthy donor, as well as peripheral blood and spleen lymphocytes from several experimental animals, in the absence of known or deliberate sensitization, were found to be spontaneously cytotoxic in vitro for some normal fresh cells, most cultured cell lines, immature hematopoietic cells, and tumor cells. This type of nonadaptive, non-MHC-restricted cellmediated cytotoxicity was defined as “natural” cytotoxicity, and the effector cells mediating natural cytotoxicity were functionally defined as natural killer (NK) cells. The existence of NK cells has prompted a reinterpretation of both the studies of specific cytotoxicity against spontaneous human tumors and the theory of immune surveillance, at least in its most restrictive interpretation. Unlike cytotoxic T cells, NK cells cannot be demonstrated to have clonally distributed specificity, restriction for MHC products at the target cell surface, or immunological memory. NK cells cannot yet be formally assigned to a single lineage based on the definitive identification of a stem cell, a distinct anatomical location of maturation, or unique genotypic rearrangements.

Biology of natural killer cells.

Two molecular mechanisms of T cell-mediated cytotoxicity, one perforin-based, the other Fas-based, have been demonstrated. To determine the extent of their contribution to T cell-mediated cytotoxicity, a range of effector cells from normal control or perforin-deficient mice were tested against a panel of target cells with various levels of Fas expression. All cytotoxicity observed was due to either of these mechanisms, and no third mechanism was detected. Thus, the perforin- and Fas-based mechanisms may account for all T cell-mediated cytotoxicity in short-term in vitro assays.

https://science.sciencemag.org/content/sci/265/5171/528.full.pdf

Fas and Perforin Pathways as Major Mechanisms of T Cell-Mediated Cytotoxicity

Publisher Summary The term “cell-mediated cytotoxicity” applies to lytic reactions that require the participation of lymphoid or non-lymphoid cells but not of added complement. It has been clearly established that several pathways, including different cell types, are involved in cytotoxic reactions in vitro. With membrane-associated antigens, such as transplantation, and tumor-associated antigens, the cytotoxic effect of effector cells on adequate target cells is most often highly specific and requires intimate contact rather than release of diffusible toxic factors. Specific cell-mediated cytotoxicity in vitro can be divided into three categories according to the nature of the effector cells.

Cell-Mediated Cytotoxicity, Allograft Rejection, and Tumor Immunity

Publisher Summary This chapter discusses the interactions of lectins with animal cell surfaces. Lectin interactions with cell surfaces can be put into a proper framework for understanding complex phenomena such as lectin-induced mitogenic stimulation, cell agglutination, and lectin-mediated cell toxicity. Lectins have been isolated from a wide variety of plants and animals, from legumes to horseshoe crabs. Lectins generally have the property of agglutinating cells through their cell surface oligosaccharide determinants, and in some cases these determinants have been elucidated by determining the sequences or sugars responsible for saccharide inhibition of agglutination. Because of the carbohydrate-binding specificities of lectins, some of these agglutinins have proven to be quite useful for clinical blood typing and structural studies of blood group substances, in analysis of the surface structure of normal and tumor cells, for specific isolation of glycoproteins and oligo- and mucopolysaccharides, in studies on mitogenesis, as antigen-antibody models, and so on. They have also proven to be invaluable as specific molecular probes for studying membrane, cell, and tissue structure and organization.

The interactions of lectins with animal cell surfaces.

Malignant Lymphomas Other than Hodgkin’s Disease

Publisher Summary This chapter discusses the cytotoxic effects of lymphoid cells in vitro. The chapter discusses the complex problem of different types of cytotoxic effects of lymphoid cells. These outstanding workers in the field have managed to present a cohesive picture of the various effects on the target cells. The role of “nonspecific” factors is particularly well clarified. The interrelationships among contact lysis, release of pharmacologically active substances, and the terminal components of the complement system are given in the chapter for special consideration. In an in vitro model, it is shown that lymphoid cells from sensitized donors destroy tissue culture cells carrying the antigen to which the cell donor is sensitized. This type of cytolytic reactions is encountered in a great variety of immune situations, comprising all those mentioned in the chapter. The cell that initiates in vitro cytotoxic reaction is assumed to be the sensitized lymphocyte, equipped with its own recognition sites for antigen on the cells that are destroyed. Although this may be true in many situations, it now seems clear that “normal” lymphoid cells can become cytotoxic to other cells by a variety of pathways. The study of the various pathways by which lymphoid cells can become cytotoxic has been helpful for the understanding of effector role of these cells in cell-destructive reactions in general.

Cytotoxic effects of lymphoid cells in vitro.

Phytohaemagglutinin-Induced Cytotoxic Action of Normal Lymphoid Cells on Cells in Tissue Culture

Phytohaemagglutinin-induced cytotoxic action of normal lymphoid cells on cells in tissue culture.

Viable and immunologically competent lymphocytes from unsensitized donors damage allogeneic tissue culture cells in the presence of phytohemagglutinin (PHA). This cytotoxicity is specific since syngeneic tissue culture cells are not at all or only slightly damaged under similar experimental conditions. In this investigation, the relation between the stimulation of human lymphocytes and their cytotoxicity was studied. Chang cells (human liver) served as target cells in all experiments. Cell damage was quantitated by measuring the release of isotope from target cells labeled with chromate-51Cr.

The cytotoxicity of the lymphocytes was dependent on the concentration of PHA in the incubation medium. Cell damage was maximal at concentrations of 4–8 µl PHA/ml. Higher concentrations were inhibitory although aggregation was increased and no injury of the lymphocytes was noted. Stimulation of DNA and RNA synthesis in PHA-treated lymphocytes each followed dose response curves which were similar to that of cytotoxicity.

In order to establish whether stimulation without mixed aggregation of lymphocytes and target cells would suffice for cytotoxicity, a series of nonagglutinating stimulants were investigated. Lymphocytes pretreated with a crude filtrate of Staphylococcus aureus for periods of 0.5–72 hr damaged Chang cells even in the absence of PHA. Lymphocytes from a tuberculin-positive donor were strongly cytotoxic after prestimulation with PPD while those from a negative donor were inactive. Moreover, strong cytotoxic effects were also obtained with lymphocytes which had been stimulated by preincubation with allogeneic lymphocytes in mixed culture. When two stimulants were applied at the same time, additive cytotoxic effects were seen. Addition of PHA to the lymphocyte/Chang cell mixtures potentiated the cytotoxicity of prestimulated lymphocytes. The cytotoxic potential of the lymphocytes was in all cases correlated to the degree of stimulation recorded as transformation into blast cells, and was independent both of the degree of aggregation and of the stimulating factor.

These findings are compatible with the assumption that injury of the Chang cells reflected an immunologically nonspecific activity of lymphocytes enhanced by stimulation. The possible importance of this activity for a number of tissue-damaging immune reactions in vivo is pointed out.

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Cytotoxic potential of stimulated human lymphocytes

Phytohaemagglutinin-induced Cytotoxic Action of Unsensitized Immunologically Competent Cells on Allogeneic and Xenogeneic Tissue Culture Cells

Phytohaemagglutinin-induced cytotoxic action of unsensitized immunologically competent cells on allogeneic and xenogeneic tissue culture cells.

Fowl erythrocytes are lysed when exposed to an excess of fowl blood lymphocytes in the presence of phytohemagglutinin. No significant cell damage is seen in the absence of phytohemagglutinin, or when the lymphocytes are replaced by malignant lymphoid cells, thymus cells, or nonlymphoid cells. The lymphocytes remain viable during the reaction. Differences in histocompatibility between lymphocytes and erythrocytes are not required. Autologous lymphocytes are cytotoxic to the same extent as allogenic lymphocytes over a wide range of experimental conditions.

http://science.sciencemag.org/content/sci/160/3825/306.full.pdf

Göran Holm

Papers

Cytotoxic effects of lymphoid cells in vitro.

Phytohaemagglutinin-induced cytotoxic action of normal lymphoid cells on cells in tissue culture.

Cytotoxic potential of stimulated human lymphocytes

Phytohaemagglutinin-induced cytotoxic action of unsensitized immunologically competent cells on allogeneic and xenogeneic tissue culture cells.

Cytotoxic Action of Stimulated Lymphocytes on Allogenic and Autologous Erythrocytes