Boursalian T E, Bottomly K
Section of Immunobiology, Yale University School of Medicine, Howard Hughes Medical Institute, New Haven, CT 06520, USA.
J Immunol. 1999 Apr 1;162(7):3795-801.
The diversity of naive CD4 T cells plays an important role in the adaptive immune response by ensuring the capability of responding to novel pathogens. In the past, it has been generally accepted that naive CD4 T cells are intrinsically long-lived; however, there have been studies suggesting some CD4 T cells are short-lived. In this report, we identify two populations of naive CD4 T cells: a long-lived population as well as a short-lived population. In addition, we identify two factors that contribute to the establishment of long-lived naive CD4 T cells. We confirm earlier findings that MHC class II interaction with the TCR on CD4 T cells is important for survival. Furthermore, we find that MHC class II alleles with the correct restriction element for Ag presentation mediate the peripheral survival of naive CD4 T cells more efficiently than other positively selecting alleles, regardless of the selecting MHC in the thymus. The second component contributing to the survival of naive CD4 T cells is contact with the cytokines IL-4 and IL-7. We find that the physiological levels of IL-4 and IL-7 serve to enhance the MHC class II-mediated survival of naive CD4 T cells in vivo.
初始CD4 T细胞的多样性通过确保对新病原体的应答能力在适应性免疫反应中发挥重要作用。过去，人们普遍认为初始CD4 T细胞本质上寿命较长；然而，有研究表明一些CD4 T细胞寿命较短。在本报告中，我们鉴定出了两类初始CD4 T细胞群体：一类寿命较长，另一类寿命较短。此外，我们还确定了两个有助于建立长寿初始CD4 T细胞的因素。我们证实了早期的发现，即MHC II类分子与CD4 T细胞上的TCR相互作用对细胞存活很重要。此外，我们发现具有正确抗原呈递限制元件的MHC II类等位基因比其他阳性选择等位基因更有效地介导初始CD4 T细胞的外周存活，无论胸腺中的选择MHC如何。促成初始CD4 T细胞存活的第二个因素是与细胞因子IL-4和IL-7的接触。我们发现，IL-4和IL-7的生理水平有助于在体内增强MHC II类分子介导的初始CD4 T细胞存活。
