Ruggiero G, Martinez Cáceres E, Voordouw A, Noteboom E, Graf D, Kroczek R A, Spits H
Division of Immunology of the Netherlands Cancer Institute, Amsterdam.
J Immunol. 1996 May 15;156(10):3737-46.
Human thymic epithelial cells express CD40, so we examined the possible role of CD40 in activation of thymocytes. We observed that both CD4+CD8- and CD4-CD8+ thymocytes proliferate after stimulation by anti-CD3 mAb in the presence of cultured thymic epithelial cells. Costimulation of CD4+ thymocytes by thymic epithelial cells is partly inhibited by an anti-CD40 mAb, but this mAb has no effect on costimulation of CD8+ thymocytes. The selective costimulatory ability of CD40 for CD4+ thymocytes was confirmed in experiments in which thymocytes were stimulated with anti-CD3 in the presence of murine P815 cells transfected with CD40 cDNA. The level of costimulation induced by P815-CD40 was comparable with that induced by P815 cells expressing CD80 (B7.1). Treatment of thymocytes with the Ca2+ ionophore ionomycin and the phorbol ester PMA or with anti-CD3 mAb resulted in up-regulation of the CD40 ligand, suggesting that this molecule is involved in CD40-mediated costimulation of human thymocytes. Costimulation of thymocytes by CD80 strongly increased anti-CD3-induced death of fetal thymocytes. In contrast, costimulation by CD40 did not increase anti-CD3-mediated apoptosis of these thymocytes. To confirm that CD40 does not affect anti-CD3-induced cell death, we established a variant of the Jurkat T leukemic cell line that constitutively expresses CD40L and analyzed the sensitivity of this cell line for activation-induced apoptosis. In contrast to CD80, CD40 failed to increase anti-CD3-mediated apoptosis in CD40L+ Jurkat cells, whereas both CD40 and CD80 strongly increased IL-2 production induced by anti-CD3. These findings suggest that costimulation by CD40 is involved in clonal expansion of CD4+ thymocytes but not in activation-induced cell death.
人类胸腺上皮细胞表达CD40，因此我们研究了CD40在胸腺细胞激活中的可能作用。我们观察到，在培养的胸腺上皮细胞存在的情况下，抗CD3单克隆抗体刺激后，CD4⁺CD8⁻和CD4⁻CD8⁺胸腺细胞都会增殖。胸腺上皮细胞对CD4⁺胸腺细胞的共刺激作用部分被抗CD40单克隆抗体抑制，但该单克隆抗体对CD8⁺胸腺细胞的共刺激作用没有影响。在用转染了CD40 cDNA的小鼠P815细胞存在的情况下，用抗CD3刺激胸腺细胞的实验中证实了CD40对CD4⁺胸腺细胞的选择性共刺激能力。P815-CD40诱导的共刺激水平与表达CD80（B7.1）的P815细胞诱导的水平相当。用钙离子载体离子霉素和佛波酯PMA或抗CD3单克隆抗体处理胸腺细胞会导致CD40配体上调，这表明该分子参与了CD40介导的人类胸腺细胞共刺激。CD80对胸腺细胞的共刺激强烈增加了抗CD3诱导的胎儿胸腺细胞死亡。相比之下，CD40的共刺激并没有增加这些胸腺细胞的抗CD3介导的凋亡。为了证实CD40不影响抗CD3诱导的细胞死亡，我们建立了一个组成性表达CD40L的Jurkat T白血病细胞系变体，并分析了该细胞系对激活诱导凋亡的敏感性。与CD80不同，CD40未能增加CD40L⁺Jurkat细胞中抗CD3介导的凋亡，而CD40和CD80都强烈增加了抗CD3诱导的IL-2产生。这些发现表明，CD40的共刺激参与了CD4⁺胸腺细胞的克隆扩增，但不参与激活诱导的细胞死亡。
