Department of Dermatology, University at Buffalo, Buffalo, New York, USA.
J Am Acad Dermatol. 2011 Jul;65(1):106-11. doi: 10.1016/j.jaad.2010.06.019. Epub 2011 May 12.
Direct immunofluorescence is useful in the diagnosis of autoimmune, vesiculobullous, and connective tissue diseases. Michel medium is typically indicated for transport, but clinicians may inadvertently place samples into formalin.
We set out to determine the amount of time that specimens can remain in 10% buffered formalin and still retain their diagnostic properties.
Biopsy samples were examined from cases with established diagnoses of bullous pemphigoid (n = 12), dermatitis herpetiformis (n = 6), and pemphigus vulgaris (n = 6) and exposed to formalin for time points ranging from 2 minutes to 4 hours.
We found that immunoreactants were detectable in the majority of samples when subjected to 2 minutes of formalin exposure. Dermatitis herpetiformis and pemphigoid samples retained immunogenicity for 10 minutes, whereas pemphigus showed reduced immunogenicity for all samples studied. A nonimmunologic nuclear fluorochroming pattern was noted in some of the specimens after formalin immersion.
Sample size, only examining 3 disease processes, and samples already having been in Michel medium were the major limitations in the study.
In direct immunofluorescence studies, formalin exposure to biopsy specimens causes two types of artifactual changes: (1) the shortest exposure (2 minutes) causes complete loss of diagnostic markers of pemphigus; and (2) prolonged exposure changes tissue to a form that allows fluorescein-labeled antibodies to give fluorochroming reactions of nuclei (which can be mistaken for in vivo antinuclear antibody reactions of lupus erythematosus). After time intervals of 10 minutes to 2 hours, direct immunofluorescence studies of proven cases of bullous pemphigoid and dermatitis herpetiformis retained variable levels of specific reactivity.
直接免疫荧光在自身免疫性、水疱性和结缔组织疾病的诊断中很有用。米歇尔培养基通常用于运输，但临床医生可能会无意中将样本放入福尔马林。
我们旨在确定标本在 10%缓冲福尔马林中的保留时间，并且仍然保留其诊断特性。
从已确诊的大疱性类天疱疮（n=12）、疱疹样皮炎（n=6）和寻常性天疱疮（n=6）的病例中检查活检样本，并将其暴露于福尔马林的时间点从 2 分钟到 4 小时不等。
我们发现，在暴露于福尔马林 2 分钟的大多数样本中可以检测到免疫反应物。疱疹样皮炎和大疱性类天疱疮样本保留免疫原性 10 分钟，而寻常性天疱疮的所有样本的免疫原性均降低。在福尔马林浸泡后，一些标本中出现了非免疫性核荧光染色模式。
样本量小、仅检查 3 种疾病过程以及样本已经在米歇尔培养基中是研究中的主要限制。
在直接免疫荧光研究中，福尔马林暴露于活检标本会导致两种类型的人为变化：（1）最短暴露（2 分钟）导致寻常性天疱疮的诊断标志物完全丧失；（2）长时间暴露会使组织变成一种形式，使荧光标记的抗体产生核荧光染色反应（这可能会被误认为是红斑狼疮的体内抗核抗体反应）。在 10 分钟到 2 小时的时间间隔后，对已确诊的大疱性类天疱疮和疱疹样皮炎病例进行的直接免疫荧光研究保留了可变水平的特异性反应。
