Objective: To evaluate the quantitative and functional changes of T helper (Th) cell subsets in the bone marrow of severe aplastic anemia (SAA) patients and the relationship between these changes and the patients hematopoietic function.
Methods: By FACS, the quantity and ratio of Th1 and Th2 cells, the percentage of CD3(+)CD8(+) cells in the bone marrow were detected in 24 patients with SAA at active phase, 15 patients with SAA at recovery phase, and 16 normal controls. By radioimmunoassay, the serum levels of TNF-alpha, or IL-4 in 20 SAA patients at active phase, 12 at recovery phase and 16 normal controls were measured. The relationships between CD3(+)CD8(+) cells, TNF-alpha and Ret, ANC; and between Th1 cells and CD3(+)CD8(+) cells, TNF-alpha or Ret, ANC; between IL-4, balance of Th1/Th2 and Ret, ANC were evaluated.
Results: The percentages of Th1 and Th2 cells, and ratio of Th1/Th2 in bone marrow of SAA patients at active phase were (4.87 +/- 2.64)%, (0.41 +/- 0.26)% and 21.22 +/- 5.07, respectively, being higher than those of normal controls [(0.42 +/- 0.30)% (P < 0.01), (0.24 +/- 0.17)% (P < 0.05) and (1.57 +/- 0.93) (P < 0.01), respectively] and all of them reduced to normal levels of SAA at recovery phase (P > 0.05). The percentage of CD3(+)CD8(+) cells significantly decreased from (32.32 +/- 8.69)% at active phase to (13.76 +/- 2.96)% at recovery phase (P < 0.01). The serum levels of TNF-alpha and IL-4 at active phase was (4.29 +/- 3.15) microg/L and (1.24 +/- 0.73) microg/L, respectively, being higher than those of normal controls (1.21 +/- 1.16) microg/L, (1.18 +/- 0.97) microg/L, but only the difference of TNF-alpha was statistically significant (P < 0.01). In recovery SAA patients, the serum levels of TNF-alpha significantly decreased to (1.46 +/- 1.41) microg/L (P < 0.01), and the levels of IL-4 increased markedly to (3.05 +/- 1.94) microg/L. The CD3(+)CD8(+) cells and TNF-alpha of patients negatively correlated with Ret (P < 0.05; P < 0.05) and ANC (P < 0.05; P < 0.05), Th1 cells correlated with CD3(+)CD8(+) cells and TNF-alpha positively (P < 0.01; P < 0.05), the Ret and ANC negatively (P < 0.01; P < 0.01), IL-4 and the balance of Th1/Th2 positively correlated with Ret and ANC (P < 0.05, P < 0.01; P < 0.01, P < 0.01).
Conclusion: The bone marrow failure in SAA might be caused not only by the increase of Th1 cells, Th1 type effector cells and cytokines, but also by insufficient compensation of Th2 cells and Th2 type cytokines, which shifted the balance of Th1/Th2 favorable to Th1.