Evolution and ecology of influenza A viruses.

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 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.

Publisher Summary This chapter illustrates several ways in which radiation may be employed to dissect several individual cellular components of the immune response. The chapter considers the interrelationships between radiation and the various components of the immune response from three perspectives: (1) the effect of irradiation on normal lymphoid tissues and on isolated lymphocytes, (2) the effect of irradiation on antibody production, transplantation immunity, and other forms of cellular immunity, and (3) the effect of irradiation upon tolerance with specific references to putative autoimmune consequences after radiation-induced alterations in normal immunological homeostasis. A wide variety of approaches are available to characterize and define distinct populations of lymphocytes. These include biophysical and functional methods and characterization of antigenic and cell surface receptor components. The mechanisms of radiation effects in biological systems, particularly in humans, have been derived from experiments utilizing cells exposed in vitro and maintained in tissue culture. Such cells can be examined for: (1) loss of viability, (2) alterations in biophysical structure, (3) loss of functional capabilities, (4) biochemical changes, and (5) evidence of injury to subcellular components.

Ionizing radiation and the immune response.

An immunologically specific cellular cooperation may resolve the paradox that immune spleen cells injected into normal mice prevent the growth of lymphoma cells in vivo but fail to do so in vitro.

Cooperation of Immune Lymphoid Cells with Macrophages in Tumour Immunity

Summary: Spleen cells from C57BL mice immunised once with L5178Y lymphoma cells, which are of DBA/2 genotype, were assayed for cytotoxicity by measuring their effect on the growth of L5178Y cells in vitro. Two populations of cytotoxic spleen cells were distinguished: (1) those found predominantly 6-12 days following immunisation; and (2) those found 14 days and later following immunisation. The cytotoxic activity of the “early” cells was relatively radioresistant and was not affected by drugs which inhibit nucleic acid synthesis. These early cells resemble those found in lymph from draining nodes, which are cytotoxic only 4-8 days after immunisation. Spleen cells taken from mice and rats 21 days after immunisation lost cytotoxic activity by exposure to 500 R of X-rays and to Mitomycin C, actinomycin D, and potassium cyanide. Removal of macrophages did not reduce the cytotoxicity of either class of spleen cell. Cytotoxicity was unaffected by the addition of a source of complement, but this does not exclude the participation of some complement components (which are synthesised by spleen cells). By following the release of 61Cr, it was shown that the L5178Y cells lysed sooner after the addition of spleen cells taken at 7 days, as compared to 21 days, after immunisation. The 21-day spleen cells acquired some of the properties of 7-day spleen cells (such as radioresistance) after exposure to target cells for 10 hr. The hypothesis is advanced that the cells responsible for cytotoxicity in spleens at 7 days after immunisation are immunoblasts (i.e., large pyroninophilic cells), as had earlier been shown to be the case for cells in the lymph from immunised donors. These cells, it is postulated, are directly cytotoxic, possibly because they already possess the machinery for the synthesis of antibody. The cells found in spleen 21 days after immunisation are only potentially cytotoxic and become transformed—hence their radiosensitivity—by contact with target cell antigen into the actual cytotoxic cells, which are presumably immunoblasts

The occurrence of two types of cytotoxic lymphoid cells in mice immunised with allogeneic tumour cells.

SUMMARY Efferent lymph from a single lymph node that had been stimulated antigenically with L5178Y mouse lymphoma cells was collected from each of eight sheep. The cytotoxic activity of the washed lymph cells was assayed in terms of their ability to inhibit the growth of lymphoma cells in vitro. The cells from lymph collected between 90-150 hr after antigenic stimulation were highly cytotoxic. The strength of the cytotoxic action correlated with the number of large basophilic lymph cells (immunoblasts) present in the lymph; it is to these cells that we attribute the cytotoxic activity. The cytotoxic action of these cells appeared to be immunologically specific; lymph cells from sheep that had been immunized with bacterial antigens were without cytotoxic activity even though large numbers of immunoblasts were present. Small lymphocytes, as such, whether from immunized or unimmunized sheep, appeared to have no cytotoxic activity. The mechanism of the cytotoxie action is unknown, but in this particular system an important role for specific antibody cannot be excluded.

The nature of the cytotoxic cells in lymph following primary antigenic challenge.

Evidence for the role of antibody in the cytotoxic action of lymph cells on xenogeneic target cells.

L5178Y lymphoma cells from DBA/2 mice grow well in vitro and the cytotoxicity of immune lymphoid cells can be assayed easily in terms of the degree to which they inhibit the growth of the lymphoma. Using this system we have already shown that sheep lymph cells, collected from the efferent ducts of individual lymph nodes that had been immunized with the lymphoma, displayed a powerful and immunologically specific cytotoxic action1. The cytotoxicity of the lymphoid cell population correlated with the percentage of large basophilic immunoblasts that were present and consequently an unequivocal cytotoxic action was only demonstrable between 4–7 days after immunization when large numbers of immunoblasts were present in the lymph. At later times the lymph was populated mainly with small lymphocytes and these cells, even when collected from hyperimmune sheep, were without demonstrable cytotoxic action in vitro. For these reasons it was concluded that the immunoblast was the cytotoxic cell. In these experiments the lymphoma cells were cultured in a medium containing 10 per cent heat-inactivated foetal calf serum.

Antibody and complement-like factors in the cytotoxic action of immune lymphocytes.

SUMMARY Ten days or more alter sheep had been immunized s.c. with murine lymphoma cells, cytotoxic white cells were present in the blood but were absent from intermediate lymph. This cytotoxic activity did not require complement and was not reduced by exposing the blood cells to 500 It of X-irradiation; it was abolished by the removal of glassadherent cells, or by treatment with antimaerophage serum. Alt hough lymphocytes from intermediate lymph of immunized sheep were not cytotoxic, themselves, they were able 1o confer cytotoxic activity on white cells from the blood of unimnninized sheep. Similarly, lymph-borne lymphocytes from immunized sheep could confer cytotoxic activity on monolayers of macrophages obtained from the udders of normal ewes. When lymph cells from an immunized sheep were incubated in vitro with irradiated lymphoina cells, a soluble factor was released into the supernatant which induced cytotoxic activity in the white cells from the blood of normal sheep. It, was concluded that, alter immunization the regional nodes release a population of lymphocytes that are sensitized but not cytotoxic. When such cells reencounter the antigen they produce a factor which induces cytotoxieitv in a subpopiilation of mononuclear effector cells which are present in blood and peripheral tissues but not in intermediate, lymph. There is compelling circumstantial evidence thai these effector cells belong to the monoeyte-macrophage series, but at present we prefer to describe them merely as blood-borne cytotoxic cells.

The nature of blood-borne cytotoxic cells. I. Cooperation between the white cells of the blood and lymph of sheep in the destruction of xenogeneic tumour cells in vitro.

P Alexander

Papers

The occurrence of two types of cytotoxic lymphoid cells in mice immunised with allogeneic tumour cells.

The nature of the cytotoxic cells in lymph following primary antigenic challenge.

Evidence for the role of antibody in the cytotoxic action of lymph cells on xenogeneic target cells.

Antibody and complement-like factors in the cytotoxic action of immune lymphocytes.

The nature of blood-borne cytotoxic cells. I. Cooperation between the white cells of the blood and lymph of sheep in the destruction of xenogeneic tumour cells in vitro.