Taylor M J, Bank H L, Benton M J
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston 29425.
Diabetes Res. 1987 Jun;5(2):99-103.
Recent developments in transplantation immunobiology, concerning the mechanism of tissue rejection, clearly indicate that antigen recognition alone is not sufficient for lymphocyte activation. "Passenger" leucocytes (antigen presenting cells) carried in the donor tissue are now recognized as the major immunogenic stimulus, such that removal of these contaminating leucocytes, using a variety of procedures, has enabled the immunogenicity of allografts to be reduced and the survival of the graft to be significantly extended. Remarkable advances have been made in recent years in preventing rejection of islet allografts, and even xenografts, in experimental animals by using procedures which do not involve continuous immunosuppressive therapy. Cryopreservation offers not only the means by which donor tissue can be stored effectively during such procedures but also the possibility that, under appropriate conditions, the freezing and thawing process itself could modulate tissue immunogenicity by allowing the selective killing of immunocompetent leucocytes whilst preserving the function of parenchymal cells in the graft. In this preliminary study we have characterized the survival of leucocytes and islets from the same species (rat) after cryopreservation by the same technique using dimethyl sulphoxide (Me2SO) as the cryoprotectant. Optimum survival of rat lymphocytes and macrophages was found at cooling rates in the range of 0.3-5 degrees C/min, after cooling at rates greater than 75 degrees C/min, survival was reduced to a negligible level. On the other hand, recovery of islets was 73 +/- 9% at 75 degrees C/min, indicating that depletion of lymphoid cells, with satisfactory preservation of endocrine cells, should be obtainable at this cooling rate.
移植免疫生物学在组织排斥机制方面的最新进展清楚地表明，仅抗原识别不足以激活淋巴细胞。供体组织中携带的“过客”白细胞（抗原呈递细胞）现在被认为是主要的免疫原性刺激物，因此，通过各种程序去除这些污染的白细胞能够降低同种异体移植物的免疫原性，并显著延长移植物的存活时间。近年来，通过使用不涉及持续免疫抑制治疗的程序，在防止实验动物中的胰岛同种异体移植甚至异种移植排斥方面取得了显著进展。冷冻保存不仅提供了在这些程序中有效储存供体组织的方法，而且还提供了一种可能性，即在适当条件下，冷冻和解冻过程本身可以通过选择性杀死免疫活性白细胞同时保留移植物实质细胞的功能来调节组织免疫原性。在这项初步研究中，我们通过使用二甲基亚砜（Me2SO）作为冷冻保护剂的相同技术，对同一物种（大鼠）的白细胞和胰岛在冷冻保存后的存活情况进行了表征。发现大鼠淋巴细胞和巨噬细胞在0.3 - 5℃/分钟的冷却速率下存活率最佳，在冷却速率大于75℃/分钟后，存活率降至可忽略不计的水平。另一方面，在75℃/分钟时胰岛的回收率为73±9%，这表明在该冷却速率下应该能够实现淋巴细胞的耗竭，同时内分泌细胞得到满意的保存。
