Accessory Cell Populations Research Articles

Generation of cytolytic T lymphocytes in vitro. XI. Accessory cell requirement in secondary responses to particulate alloantigen.

The non-T accessory cell requirement for cytolytic T lymphocyte (CTL) generation in vitro was studied in a system which makes use of particulate membrane preparations as a source of alloantigen, and spleen cells from alloimmune mice as a source of responding cells. It is shown that removal of nylon-adherent cells from the responding cell population strongly reduced CTL generation, whereas direct removal of Ig+, phagocytic or plastic-adherent cells had no effect. The CTL response of the nylon-nonadherent cell population could be reconstituted by the addition of normal spleen cells, which by themselves do not generate CTL in response to particulate alloantigen. The accessory cell function of normal spleen cells was not affected by depletion of T cells or of phagocytic cells, but was sensitive to gamma-irradiation (1000 rd). The system thus demonstrates the requirement for a nylon-adherent accessory cell population in the secondary CTL response to particulate alloantigens which does not exhibit the typical characteristics of T cells, B cells or macrophages.

Cell-Mediated Immune Response to Syngeneic UV-Induced Tumors

Abstract An Ia-positive accessory cell with macrophage characteristics was demonstrated to be required for the in vitro proliferation and differentiation of lymph node T lymphocytes from tumor-immunized mice into cytotoxic T lymphocytes (CTL). An experimental system is described that provides for the measurement of both proliferation and CTL capacity in in vitro cultures of draining lymph node (DLN) cells from tumor-immunized mice. DLN cells obtained from the popliteal lymph nodes of mice immunized in the hind footpads with a syngeneic UV-induced fibrosarcoma proliferate and differentiate into highly effective CTL (as assessed in a 6-hr chromium release assay) when placed in culture without the addition of tumor antigen. Both proliferation and CTL generation by DLN cells in vitro were shown to result from the interaction of at least two physically separable cell populations: a T cell population responsible for the proliferation and expression of CTL activity, and an accessory cell population required for the expression of the T cell functions. The accessory cell was shown to be resistant to γ-radiation, adherent to nylon and glass wool columns, sensitive to treatment with anti-Ia antisera plus complement (C), and resistant to treatment with anti Thy-1 antisera plus C. Antigen presentation did not appear to be required for effective cooperation between lymphocytes from tumor-immunized mice and accessory cells, although antigen presentation did occur when unprimed lymphocytes were mixed with accessory cells present in the DLN of tumor-immunized mice. The regulation of CTL development and the role of the Ia-positive accessory cell in anti-tumor immunity are discussed.

Expression of I-Subregion Encoded Antigens on Accessory Cell Populations

Abstract We have investigated the expression of Ia antigens on accessory cells which function in two murine response systems: the proliferative response to Con A and the in vitro primary antibody response to soluble TNP-conjugated protein antigens. Pretreatment of murine lymphoid cells with anti-Ia and complement (C) abrogated their ability to respond to Con A. Reconstruction experiments have shown that glass adherent spleen cells treated with a T cell-specific rabbit anti-mouse brain serum and C and irradiated with 1000R (spleen-adherent cells, SAC) were able to restore responsiveness to Con A. In a second assay system, T cell-dependent IgM responses of normal spleen cells to soluble TNP-conjugated protein antigens were abrogated by Sephadex G-10 passage. Responses in this system were similarly reconstituted by the addition of non-T, non-B, radioresistant SAC as accessory cells.

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.