| Purpose To observe the characteristics and lagularity of immune reconstitution in patients with acute leukemia after unrelated cord blood stem cell transplantation (UCBT), especially the characteristics of NK cells and their surface receptors .and to probe the preliminary celluar basis for early effect of GVL after UCBT.. Methods From October 2006 to August 2008, 11 cases with acute leukemia underwent UCBT in Anhui Provincial Hospital. The immune reconstitution of NK cells and their surface receptors as well as T/B cells within 180 days after UCBT was measured by flow-cytometry .Besides, they were compared with the immune recovery of 11 patients who received peripheral blood (PB) combined with bone marrow (BM) transplantation at the same period .Results After UCBT, CD3-56+NK and CD3-CD16+NK accounted for (35.12±18.66)% and (10.00±5.92)% of peripheral blood lymphocytes respectively on the day of clinical engraftment (Ed) .Besides, The value of the CD3-56+ and CD3-CD16+NK at 30 days after transplantation accounted for (37.8±17.52)% and (16.72±11.3)% of lymphocyte separately, the proportion of CD56+NK cells reached its peak at that time.On 60days after transplantation , CD56+NK and CD16+NK cells were 13.4±12.16%and 13.72±11.29% respectively,while the absolute count of CD56+NK cells reached the peak ,up to 544cells/μl in PB, and then , CD16+NK cells reached 245cells/μl . On 90days after UCBT , CD3-56+NK and CD3-CD16+NK accounted for (18.16±17.7)% and (10.4±6.24)% respectively.They were near to each other. Along with the perfecting of cells` function, CD16+NK cells show a tendency of gradual elevation, but CD56+NK cells show a tendency of gradual decrease.The two proportion curve become cross after day90, at last,CD16+ NK exceeded CD56+NK cells.On day 180, CD56+ and CD16+ accounted(10.51±6.54)% and (19.30±6.51)% of lymphocyte respectively .and either of their absolute count were 287±123/μl and 553±168.98/μl.Compared with related PB plus BM stem cells transplantation, the recovery of NK was faster in UCBT. On ED the proportion of CD3-56+NK cells of PB lymphocytes in patients of UCBT group was higer than that in PB+BMT group(35.12±18.66Vs 20.0±5.27 p<0.03),on day 30, either proportion of CD3-56+NK in two group reached peak at the same time(37.8±17.52 Vs 37.1±7.06 p>0.05),afterwards ,they two showed the same decreasing tendency.on day 60,NK cells proportion of UCBT group exceeded that of PB+BMT group once again,(30.4±19.14 Vs 12.6±4.96 p<0.05).Then, NK cells in PB+BMT group restored relative quickly and a little bit higher than in UCBT group on day 90(23.4±8.52 Vs 18.15±8.17 p>0.05). The reconstitution of active receptor NKG2D is fast and hyper-expressing continuely. Compared with related PB+BMT stem cells transplantation ,NKG2D recovery was faster, even on ED it is(79.58±8.71%Vs 36.7±14.33% p<0.03),and kept superiority on day 30(80.03±13.49% Vs 56.8±18.21%,p<0.035).On day 60,their level appeared to be equa(82.55±9.10%Vs 82.3±28.64%, p>0.05),And on day 90 it went to the contrary( 85.82±18.21%Vs 90.3±27.89%, p<0.01).On the other hand, the reconstitution of inhibitory NK receptors NKG2A was relatively late in patients of UCBT group, Its level was lower than that of PB+BMT group(63.9±7.47%Vs 90.3±15.35%, p<0.01)and kept this tendency on day 30(64.18±10.3%Vs 82.1±25.68%, p<0.03),but it gradually elavated and exceeded the level in patients of PB+BMT group after day 60,As to the recontitution of T cells, It is relatively later in UCBT recipients than in recipients of PB+BMT until day 90(p<0.05).Conclusion The reconstitution of NK cells in UCBT recipients with acute leukemia is relatively earlier with a higher NK NK cell proportion.. In UCBT recipients, the recontruction of NK cell surface active receptors(especially NKG2D)is quickly and hyper-expressing. and the inhibitory receptor reconstitution is relatively late.Comparing with PB plus BMT group The reconstruction of NKG2D is significantly early and NKG2A was significantly later. The reconstitution of T cells was later than the PB+BMT group . suggests that the activation of NK cell may play a role on graft versus leukemia (GVL) effect in the early period after UCBT.
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