The anti-leukemia potential of natural killer (NK) cells has been evaluated in 40 patients transplanted for chronic myelogenous leukemia (CML) to determine whether differences in NK cell function were correlated with subsequent leukemic relapse. Cells from patients and their donors were tested in 51Cr release assays against fully allogeneic CML targets and against cultured K562 targets; cells from 26 patients were tested against host-derived CML targets that were cryopreserved before transplantation. Cultured CML targets (K562) were highly susceptible to lysis by freshly isolated peripheral blood lymphocytes (PBL) and to a greater degree by PBL cultured in medium containing interleukin-2 (IL-2) in all assays performed. In contrast, noncultured CML targets were lysed only by IL-2-activated cells from a subset of patients. When present, lytic activity to CML targets was detectable as early as 3 weeks after bone marrow transplantation, and remained positive throughout the posttransplant period. Optimal lytic activity developed within the first week of culture and required greater than or equal to 250 U/mL of IL-2 in the culture medium. Lytic activity to fully allogeneic and host-derived CML targets appeared to be mediated by CD16+ and CD56+ cells but not by CD3+ cells. Lysis of allogeneic CML targets was variable, but patients could be divided into two groups: those with and those without lytic activity to the majority of targets tested. The basis for the differences in lytic activity could not be ascribed to target susceptibility to lysis, the proportion of NK cells in the cultures, or to the phenotype of the NK cell subsets in the cultures. When tested in parallel, the lytic activity of donor and recipient cultures against host-derived CML targets was highly correlated, suggesting that there may be inherent differences in the ability of NK cells to recognize CML targets. The risk of relapse for patients who failed to generate lytic activity against host-derived CML targets was significantly increased over that for patients with lytic activity against host leukemia. These data indicate that posttransplant immunotherapy with IL-2 designed to activate NK cells will likely augment the graft-versus-leukemia potential of the graft.
The anti-leukemia potential of natural killer (NK) cells has been evaluated in 40 patients transplanted for chronic myelogenous leukemia (CML) to determine whether differences in NK cell function were correlated with subsequent leukemic relapse. Cells from patients and their donors were tested in 51Cr release assays against fully allogeneic CML targets and against cultured K562 targets; cells from 26 patients were tested against host-derived CML targets that were cryopreserved before transplantation. Cultured CML targets (K562) were highly susceptible to lysis by freshly isolated peripheral blood lymphocytes (PBL) and to a greater degree by PBL cultured in medium containing interleukin-2 (IL-2) in all assays performed. In contrast, noncultured CML targets were lysed only by IL-2-activated cells from a subset of patients. When present, lytic activity to CML targets was detectable as early as 3 weeks after bone marrow transplantation, and remained positive throughout the posttransplant period. Optimal lytic activity developed within the first week of culture and required greater than or equal to 250 U/mL of IL-2 in the culture medium. Lytic activity to fully allogeneic and host-derived CML targets appeared to be mediated by CD16+ and CD56+ cells but not by CD3+ cells. Lysis of allogeneic CML targets was variable, but patients could be divided into two groups: those with and those without lytic activity to the majority of targets tested. The basis for the differences in lytic activity could not be ascribed to target susceptibility to lysis, the proportion of NK cells in the cultures, or to the phenotype of the NK cell subsets in the cultures. When tested in parallel, the lytic activity of donor and recipient cultures against host-derived CML targets was highly correlated, suggesting that there may be inherent differences in the ability of NK cells to recognize CML targets. The risk of relapse for patients who failed to generate lytic activity against host-derived CML targets was significantly increased over that for patients with lytic activity against host leukemia. These data indicate that posttransplant immunotherapy with IL-2 designed to activate NK cells will likely augment the graft-versus-leukemia potential of the graft.
During the early period following bone marrow transplantation before the immune system has reached full functional maturity, unprimed, nonspecific lytic systems may play a critical role as antiviral or antitumor effectors. The reconstitution of cells with this potential is of particular importance in recipients of bone marrow that has been depleted of mature T lymphocytes to prevent graft v host disease (GVHD). We examined the recovery of natural killer (NK) cells and interleukin 2 (IL 2)-augmented lymphokine-activated killer cells (LAK) in 48 patients at various intervals following transplantation of bone marrow depleted of mature cellular elements by treatment with soybean agglutinin and sheep RBCs (SBA-E- BMT). We found normal levels of both NK and LAK activity as early as 3 weeks following SBA-E- BMT. When compared with cells from controls, NK and LAK precursors from transplant recipients appeared to be activated in vivo in that freshly isolated peripheral blood mononuclear cells (PBMCs) from patients had an elevated cytolytic activity toward NK-insensitive targets and a more rapid response to activation by IL 2. In patients as well as controls, both LAK precursors and LAK effectors lacked antigens present on mature T lymphocytes (CD3, CD4, or CD8) but expressed antigens present on NK cells (CD2, CD16, and NKH1A). The LAK cells did not lyse either donor or host peripheral blood T cell targets. The activity of NK effectors but not LAK precursors survived the in vivo total body irradiation used for pretransplant conditioning in three patients studied. LAK precursors could be demonstrated as early as 18 days following transplant at a time when the bone marrow contained primarily donor- derived cells. Little or no LAK activity could be generated from cells of the SBA-E- BM graft itself, suggesting that LAK precursors differentiate rapidly from more primitive progenitors in the marrow graft. Thus, our data indicate that the NK and LAK lytic systems are among the earliest activities to recover during immune reconstitution following T cell-depleted BMTs.
During the early period following bone marrow transplantation before the immune system has reached full functional maturity, unprimed, nonspecific lytic systems may play a critical role as antiviral or antitumor effectors. The reconstitution of cells with this potential is of particular importance in recipients of bone marrow that has been depleted of mature T lymphocytes to prevent graft v host disease (GVHD). We examined the recovery of natural killer (NK) cells and interleukin 2 (IL 2)-augmented lymphokine-activated killer cells (LAK) in 48 patients at various intervals following transplantation of bone marrow depleted of mature cellular elements by treatment with soybean agglutinin and sheep RBCs (SBA-E- BMT). We found normal levels of both NK and LAK activity as early as 3 weeks following SBA-E- BMT. When compared with cells from controls, NK and LAK precursors from transplant recipients appeared to be activated in vivo in that freshly isolated peripheral blood mononuclear cells (PBMCs) from patients had an elevated cytolytic activity toward NK-insensitive targets and a more rapid response to activation by IL 2. In patients as well as controls, both LAK precursors and LAK effectors lacked antigens present on mature T lymphocytes (CD3, CD4, or CD8) but expressed antigens present on NK cells (CD2, CD16, and NKH1A). The LAK cells did not lyse either donor or host peripheral blood T cell targets. The activity of NK effectors but not LAK precursors survived the in vivo total body irradiation used for pretransplant conditioning in three patients studied. LAK precursors could be demonstrated as early as 18 days following transplant at a time when the bone marrow contained primarily donor- derived cells. Little or no LAK activity could be generated from cells of the SBA-E- BM graft itself, suggesting that LAK precursors differentiate rapidly from more primitive progenitors in the marrow graft. Thus, our data indicate that the NK and LAK lytic systems are among the earliest activities to recover during immune reconstitution following T cell-depleted BMTs.
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