To evaluate the feasibility of adoptive cellular immunotherapy in the treatment of acute myeloid leukemia(AML) and to search for the optimal culture condition for this treatment, peripheral blood lymphocytes(PBL) from 31 patients with AML were
cultured
and characterized in terms of expansion index, cytotoxicity, and immunologic phenotype.
PBL of both before remission and after remission were isolated from the same patient and cultured for 3 weeks under the following 4 culture conditions; 1) 1,000U/ml of recombinant interleukin-2(rIL-2) 1,000U/ml of rIL-2 and 100U/ml of recombinant
interferon-r(rIFN-r0, 3) 50U/ml of rIL-2, 4) 50U/ml of rIL-2 and 100U/ml of rIFN-r, cytotoxicity was checked against K562, Daudi, fresh autologous and allogeneic leukemic cells, and fresh autologous normal cells(PBL or bone marrow cells) using
4-hour
51Cr-release assay. Immunophenotyping was performed with monoclonal antibodies for CD3, CD56, CD4, and CD8 using flow cytometry.
PBL could expand up to 40 folds after 3 weeks of culture. PBL isolated after remission proliferated better than PBL isolated before remission, and culture in 1,000 U/ml of rIL-2 could yield more effector cells than 50U/ml of rIL-2(p<0.05). The NK
activity of fresh PBL from patents was significantly lower than in normal controls(p<0.05). Even though fresh PBL of the patents showed depressed NK activity and only negligible cytotoxicity against fresh leukemic cells, they could kill all tumor
targets very effectively after 2~3 weeks of cultured in rIL-2(p<0.05). When maximum cytotoxicity among serial measurements was compared, PBL isolaed after remission and cultured in 1,000U/ml of rIL-2 showed the greatest cytotoxicity against all
tumor
targets. The antileukemic cytotoxicity of PBL cultured in any condition seemed to be not specific for autologous leukemic cells. The cultured PBL of patents had no cytotoxicity against fresh normal cell targets. Both CD3(-)CD56(+) and
CD3(+)CD56(+)
subsets of PBL increased consistently after culture, The increase of CD3(-) CD56(+) cells coincided with the increase of cytotoxicity against all tumor targets. In regression analysis, cytotoxicity against K562 and Daudi targets was positively
correlated with the proportions of CD3(-)CD56(+) cells and CD3(+) CD56(+) cells(p<0.05), and cytotoxicity against fresh autologous leukemic cells was positively correlated with the proportion of CD3(+)CD56(-) cells(p<0.00.
These results suggest that 1) adoptive immunotherapy might play a role in the treatment of AML; 2) culture of PBL isolated after remission with 1,000U/ml of rIL-2 for 2~3 weeks could be the most effective means for this purpose; 3) Non-specific
killer
cells with surface phenotype of CD56(+) were the main effector cells for this antileukemic cytotoxicity.
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