Saalmüller A, Hirt W, Reddehase M J
Federal Research Centre for Virus Diseases of Animals, Tübingen, FRG.
Eur J Immunol. 1989 Nov;19(11):2011-6. doi: 10.1002/eji.1830191107.
The composition of the T lymphocyte population in swine is special in that in addition to the CD4-CD8+ subpopulations, CD4-CD8- and CD4+CD8- and CD4+CD8+ subpopulations are prominent in the peripheral circulating as well as in the resident T lymphocyte pools. Since the same phenotypes are characteristic of thymic populations, it was asked whether the unusual distribution in swine may result from an emigration of thymic precursor phenotypes to the periphery. This explanation was refuted, as all thymic subpopulations were found to express CD1, albeit with differences in antigen density, whereas all extrathymic subpopulations lack CD1. The cellular distribution of CD2 in swine is without precedent among all species studied. Whereas in sheep and cattle the extrathymic CD4-CD8- subpopulation is known to entirely lack CD2 and to have a low propensity for homing to lymphoid tissues, the CD4-CD8- subpopulation in swine splits into CD2+ and CD2- subsets, both of which do reside in lymphoid tissues. While CD2+CD4-CD8- T lymphocytes are rare in the circulating pool, this subset accumulates in spleen and lymph nodes. This may indicate a role for CD2 in homing. Thus the species swine is immunologically unique, not only because of having CD1-CD2+CD4+CD8+ T lymphocytes in the periphery, but also with regard to subdivision and homing behavior of its CD4-CD8- T lymphocyte subpopulation.
猪的T淋巴细胞群体组成很特殊，除了CD4-CD8+亚群外，CD4-CD8-、CD4+CD8-和CD4+CD8+亚群在周围循环以及驻留T淋巴细胞库中也很突出。由于相同的表型是胸腺群体的特征，因此有人提出猪中这种不寻常的分布是否可能是胸腺前体表型迁移到外周的结果。这种解释被驳斥了，因为发现所有胸腺亚群都表达CD1，尽管抗原密度存在差异，而所有胸腺外亚群都缺乏CD1。猪中CD2的细胞分布在所有研究的物种中都没有先例。在绵羊和牛中，已知胸腺外CD4-CD8-亚群完全缺乏CD2，并且归巢到淋巴组织的倾向较低，而猪中的CD4-CD8-亚群分为CD2+和CD2-亚群，这两个亚群都存在于淋巴组织中。虽然CD2+CD4-CD8- T淋巴细胞在循环池中很少见，但该亚群在脾脏和淋巴结中积累。这可能表明CD2在归巢中起作用。因此，猪这个物种在免疫学上是独特的，不仅因为在外周有CD1-CD2+CD4+CD8+ T淋巴细胞，还因为其CD4-CD8- T淋巴细胞亚群的细分和归巢行为。
