Matesic D, Lehmann P V, Heeger P S
Department of Medicine, Cleveland Veterans Affairs Medical Center and the Institute of Pathology, Case Western Reserve University, Ohio 44106, USA.
Transplantation. 1998 Apr 15;65(7):906-14. doi: 10.1097/00007890-199804150-00008.
Whether alloreactive T cells in a naive host derive from naive or memory T cells remains unclear. It is also unclear whether graft rejection alters the phenotype of these T cells. Proliferation assays and cytokine enzyme-linked immunosorbent assays performed on culture supernatants do not differentiate primary T-cell alloreactivity from recall responses in allograft-primed mice, suggesting that these methods are inadequate measures of the alloreactive immune repertoire.
To better characterize alloreactivity in naive and skin allograft-primed mice, we used a modified, high-resolution cytokine enzyme-linked immunosorbent spot assay capable of detecting cytokine production over short time periods.
Twenty-four-hour analysis of alloreactivity in mice that rejected fully MHC-disparate skin allografts revealed a high frequency of interferon (IFN)-gamma- and interleukin (IL)-4-producing, L-selectin-negative T cells, consistent with a memory phenotype. In contrast, 24-hr allostimulation of T cells from naive mice resulted in IL-2 production with minimal secretion of IFN-gamma or IL-4. The frequency of IL-2 producers was low and their phenotype was L-selectin positive, suggesting that they were naive and not memory T cells. When maintained in culture for 48 hr, however, the T cells from the primary mixed lymphocyte reaction began producing IFN-gamma, consistent with in vitro priming.
The primary alloresponse does not seem to involve clones that have been preprimed by environmental antigens, but instead behaves similarly to self-MHC-restricted immunity directed toward prototypic protein antigens: T cells with a naive phenotype are specifically induced to differentiate into high-frequency memory populations. These findings may have important implications for therapeutic induction of allograft tolerance.
在未经致敏的宿主中，同种异体反应性T细胞是来源于初始T细胞还是记忆T细胞仍不清楚。移植排斥是否会改变这些T细胞的表型也不明确。对培养上清液进行增殖试验和细胞因子酶联免疫吸附试验，无法区分同种异体移植致敏小鼠的原发性T细胞同种异体反应性和回忆反应，这表明这些方法不足以衡量同种异体反应性免疫库。
为了更好地表征未经致敏和皮肤同种异体移植致敏小鼠的同种异体反应性，我们使用了一种改良的高分辨率细胞因子酶联免疫斑点试验，该试验能够在短时间内检测细胞因子的产生。
对排斥完全MHC不相合皮肤同种异体移植的小鼠进行24小时同种异体反应性分析，发现产生干扰素（IFN）-γ和白细胞介素（IL）-4、L-选择素阴性的T细胞频率很高，这与记忆表型一致。相比之下，对未经致敏小鼠的T细胞进行24小时同种异体刺激，导致IL-2产生，而IFN-γ或IL-4的分泌极少。产生IL-2的细胞频率较低，其表型为L-选择素阳性，表明它们是初始T细胞而非记忆T细胞。然而，当在培养中维持48小时时，来自初次混合淋巴细胞反应的T细胞开始产生IFN-γ，这与体外致敏一致。
原发性同种异体反应似乎不涉及已被环境抗原预致敏的克隆，而是表现得类似于针对原型蛋白抗原的自身MHC限制性免疫：具有初始表型的T细胞被特异性诱导分化为高频记忆群体。这些发现可能对同种异体移植耐受性的治疗诱导具有重要意义。
