Merkenschlager M, Ikeda H, Wilkinson D, Beverly P C, Trowsdale J, Fisher A G, Altmann D M
ICRF Human Tumor Immunology Group, London.
Eur J Immunol. 1991 Jan;21(1):79-88. doi: 10.1002/eji.1830210113.
We have investigated the requirements for allogeneic stimulation of human CD4 T cells using HLA class II products expressed on various cellular backgrounds. Human (class II-negative RJ2.2.5 mutant) B cell lines transfected with HLA-DR or -DQ cDNA clones were efficient stimulators for highly purified CD4 T cells. HLA-DR-transfected mouse L cells or IFN-gamma-induced human fibroblasts, although able to function as accessory cells for T cell responses to the mitogen PHA, failed to stimulate strong T cell alloresponses. On the basis of these observations, we have employed class II transfectants to address the following questions: (a) do CD45RA and CD45R0 subpopulations differ in their allogeneic activation requirements, (b) are these subpopulations skewed in their recognition of HLA-DQ vs. HLA-DR in a manner which might support the concept that CD45RA T cells are involved in HLA-DQ-restricted suppressor inducer functions and (c) by using transfectants expressing individual HLA-DR or -DQ heterodimers in combination with limiting dilution analysis, can one for the first time obtain estimates of precursor frequencies for allogeneic cells recognizing each of these class II isotypes? Our results show that CD45RA and CD45R0 T cells respond comparably to optimal numbers of stimulator cells. However, when CD45RA and CD45R0 T cell populations depleted of endogenous accessory cells were cultured with limiting numbers of stimulator cells, CD45R0 cells generally responded more strongly, consistent with the elevated levels of various adhesion molecules known to be expressed by this population. Further, we found a similar representation of responses to HLA-DR and -DQ antigens among populations expressing CD45RA and CD45R0 isoforms. Finally, the precursor frequencies of allogeneic CD4 T cells responding to particular HLA-DR alleles were higher than to -DQ, but only by a factor of about 1.6, indicating that HLA-DQ recognition may occur more frequently than implied from previous antibody blocking studies.
我们利用在各种细胞背景上表达的HLA II类产物，研究了人类CD4 T细胞同种异体刺激的条件。用HLA-DR或-DQ cDNA克隆转染的人类（II类阴性RJ2.2.5突变体）B细胞系是高度纯化的CD4 T细胞的有效刺激物。HLA-DR转染的小鼠L细胞或IFN-γ诱导的人类成纤维细胞，虽然能够作为T细胞对丝裂原PHA反应的辅助细胞，但未能刺激强烈的T细胞同种异体反应。基于这些观察结果，我们采用II类转染细胞来解决以下问题：（a）CD45RA和CD45R0亚群在同种异体激活需求上是否存在差异，（b）这些亚群在识别HLA-DQ与HLA-DR方面是否存在偏向，这种方式是否可能支持CD45RA T细胞参与HLA-DQ限制性抑制诱导功能的概念，以及（c）通过使用表达单个HLA-DR或-DQ异二聚体的转染细胞与有限稀释分析相结合，是否能够首次获得识别每种II类同种型的同种异体细胞前体频率的估计值？我们的结果表明，CD45RA和CD45R0 T细胞对最佳数量的刺激细胞反应相当。然而，当用有限数量的刺激细胞培养耗尽内源性辅助细胞的CD45RA和CD45R0 T细胞群体时，CD45R0细胞通常反应更强，这与已知该群体表达的各种粘附分子水平升高一致。此外，我们发现在表达CD45RA和CD45R0同种型的群体中，对HLA-DR和-DQ抗原的反应具有相似的表现。最后，对特定HLA-DR等位基因作出反应的同种异体CD4 T细胞的前体频率高于对-DQ的前体频率，但仅高出约1.6倍，这表明HLA-DQ识别可能比以前的抗体阻断研究所暗示的更频繁地发生。
