Subcellular mouse alloantigens: cytotoxic immune responses and specific blocking in vitro

Cytotoxic T-lymphocytes. How do they function?

The central theme of this work has been the roles of the CTL receptor and of MHC-proteins in CTL recognition and lysis. A major conclusion that may be deduced from the work presented here is that one CTL receptor is responsible for both target cell recognition and lysis. Although their function as recognitive structures is well established, involvement of MHC-proteins in the events that follow recognition has not been investigated in detail. We have proposed that MHC-proteins are molecular mediators whereby CTL receptors transmit signals ultimately leading to lysis of the target cell. I see future work on CTL-mediated lysis proceeding in the following directions: 1. Verification and analysis of the precise role of MHC proteins in CTL recognition and lysis by use of cell and vesicle systems of defined composition and structure. 2. Study of CTL-mediated 'lethal hit' in systems enabling analysis of early events (millisecond level) preceding lysis. 3. Grafting of CTL receptor(s) activity onto naive cells, using liposomes or other vehicles, and 4. Production of idiotypic reagents such as monoclonal antibodies specific for the combining site/effector mechanism of CTL.

Generation of virus-specific cytotoxic T cells in vitro. I. Induction conditions of primary and secondary Sendai virus-specific cytotoxic T cells

H-2-restricted cytotoxic T cells specific for Sendai virus were generated in vitro in a primary response from normal mouse lymphocytes cultured in the presence of infective as well as inactivated Sendai virus. Antigen-presenting cells of different origin, including T cells, were found to be effective stimulators. Antibodies to Sendai virus were shown to inhibit the activation of specific precursor killer cells when added to cultures before, but not after, the addition of viral antigen. Data obtained by Lyt phenotyping, revealed that precursor killer cells specific for Sendai virus reside in the Lyt-2,3+ T cell population and that Lyt-1,2,3+ T cells are not required for the generation of cytotoxic lymphocytes. Different activation kinetics were demonstrated for primary and secondary antiviral cytotoxic responses, and the analysis of the proliferation and stimulation requirements suggests qualitative differences.

Factors affecting the stimulating capacity of mitogen-transformed, glutaraldehyde-treated mouse spleen cells in the mixed lymphocyte reaction

Mouse spleen cells transformed by certain mitogens and subsequently fixed with glutaraldehyde can be utilized as stimulators in the mixed lymphocyte reaction. In addition to bacterial lipopolysaccharide which has been shown previously to be effective, we have found the other B cell mitogens, dextran sulfate and Concanavalin A-Sepharose, to be functional. The ability of the treated cells to activate allogeneic cells in MLR depends upon the concentration of glutaraldehyde and the type of tissue culture medium utilized.

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.

Induction of cytotoxic lymphocytes directed against public alloantigens

The response of H-2k lymphocytes to in vitro stimulation by H-2b and HI2d spleen cells has been monitored for the production of cytotoxic lymphocytes (CL). Using cells from H-2b strains CL which were capable of lysing both H-2b and H-2d target cells (TC) were generated. These results, together with competitive inhibitor studies of the cytotoxic activity against H-2d TC, demonstrated that T lymphocytes can respond to both public and private alloantigens of the H-2 complex. When H-2d cells were used for stimulation two of the three strains tested induced CL with cytotoxic activity towards both H-2d and H-2b TC. These observations indicate that the T cell response to alloantigen, leading to the production of cytotoxic lymphocytes, can be multicomponent like the established B cell response and can be expected to be subject to as much phenotypic variation. The full complexity may only be revealed by examing a number of combinations of stimulating strains, methods of stimulation and different kinds of target cells.

Generation of T memory cells in one-way mixed lymphocyte culture. IV. Primary and secondary responses to soluble and insoluble membrane preparations and to ultraviolet-light-inactivated stimulator cells

Neither normal CBA (H-2k) nor purified spleen T cells respond in vitro to soluble or insoluble membrane preparations or to ultraviolet-light-inactivated stimulator cells of the allogeneic DBA/2 (H-2d) strain. However, CBA spleen cells deprived of phagocytic cells show a slight proliferative response under these conditions. After being primed against mitomycin-blocked DBA/2 cells in one-way mixed lymphocyte culture, the secondary blast-derived T 'memory' cells display a good secondary blast (proliferative) response to both membrane antigens and to ultraviolet-light-inactivated stimulator cells. In addition to this, the secondary T lymphocytes--in contrast to nonprimed T cells--respond by cytotoxicity when ultraviolet-light-inactivated cells are used as the second stimulant.