Cell-mediated Immunity against Allogeneic Tumor after in vitro Depletion of Histocompatibility Reactive Cells 1

Abstract

The “hot-pulse suicide” technique was first applied to lymphoid cells by Dutton and Mishell (1). The objective of this technique is to kill replicating cells in vitro by having them incorporate radioactive components such as thymidine, thereby eliminating the population proliferating in response to a specific antigen. Unidirectional mixed leukocyte cultures (MLC) “pulsed” with tri-tiated thymidine (³H-thy) of high specific radioactivity, for 3-36 hr 1 day after the initiation of the cultures were markedly inhibited in reactivity towards the stimulating cell but retained the capacity to respond to a second unrelated allogenic stimulus (2, 3). Similarly, MLC responses to a particular set of H-LA antigens can be suppressed by treatment with the thymidine analog 5-bro-modeoxyuridine (BUDR) followed by exposure to light in the visible or near visible region (4). This treatment does not significantly alter the capacity of the remaining lymphocytes to respond to cells of other H-LA specificity (4). Using the popliteal lymph node graft versus host (GVH) assay Rich et al. (5) demonstrated that Lewis rat spleen cells stimulated in mixed lymphocyte culture with F₁ hybrid spleen cells in the presence of BUDR and then treated with light did not induce local GVH response in F₁ recipients. Merino et al. (6) reported that Lewis rat spleen cells cultured with irradiated BN rat spleen cells and subjected to BUDR-light treatment are unable to elicit local GVH reaction under the kidney capsule of LBNF₁ rats but they could still elicit GVH reaction in (L/BuF)F₁ kidney. These findings suggested that GVH reactions which complicate bone marrow and lymphoid tissue transplantation could be controlled by selectively destroying the clones responding to histocompatibility antigens. Since the remaining cells retained their capacity to respond to other cellular antigens, it was possible to consider the application of the “hot pulse suicide” technique to sorting out cellular immune reactions to histocompatibility antigens from those directed against tumor specific antigens.