目的　探讨急性传染性淋巴细胞增多症(AIL)患儿外周血共刺激分子4-1BB和淋巴细胞亚群的表达及意义。方法　应用流式细胞术(FCM)检测和比较15例AIL患儿、20例急性上呼吸道感染(URI)患儿以及20例健康对照儿童的外周血4-1BB及淋巴细胞亚群的表达。结果　AIL患儿外周血4-1BB的表达及CD3+、CD4+、CD8+的表达均高于URI患儿及对照组，差异有统计学意义(P<0.05)；URI患儿与对照组间的差异则无统计学意义(P>0.05)。三组外周血CD19+CD23+的表达的差异无统计学意义(P>0.05)。AIL患儿外周血4-1BB的表达与CD3+的表达成显著正相关(r=0.73，P<0.05)。结论　4-1BB可能参与了AIL的发病。AIL患儿异常增多的T细胞可能不具备活化B细胞的功能。

Objective　To investigate expression of 4-1BB and lymphocyte subsets in peripheral blood of children with acute infectious lymphocytosis. Methods Flow cytometry (FCM) was applied to detect the expression of 4-1BB and lymphocyte subsets in peripheral blood of 15 cases of acute infectious lymphocytosis and 20 cases of acute upper respiratory infection, and 20 healthy children. Results The expression of 4-1BB and CD3+, CD4+ and CD8+ lymphocytes were higher in acute infectious lymphocytosis group than those in acute upper respiratory infection group and healthy control group (P<0.05). There was no significant difference of CD19+CD23+ lymphocytes among three groups (P>0.05). A positive correlation was found between 4-1BB expression and CD3+ lymphocytes expression in acute infectious lymphocytosis group (r=0.73, P<0.05). Conclusions The abnormal expression of 4-1BB may play a pathological role in the development of acute infectious lymphocytosis. T cells in children with acute infectious lymphocytosis may not function to activate B cells.