Improving The Sensitivity And Predictability Of Testing

作为NIEHS和FDA之间机构间协议的一部分，作为NIEHS艾滋病工作的一部分，正在进行的研究正在确定免疫细胞表型减少与感染或肿瘤易感性之间的关系。FDA James Weaver博士实验室使用抗CD4和CD8的单克隆抗体（Moabs）进行的研究已完成，以建立B6C3F1小鼠中这些细胞亚群耗竭的滴定曲线。在NIEHS，我们正在研究特定宿主抗性模型中细胞耗竭的影响。这些模型包括使用细菌（单核细胞增生李斯特菌或肺炎链球菌）、细胞内寄生虫（约氏疟原虫）或病毒（流感）的感染和肿瘤攻击（PYB 6或B16 F10）。将针对每个细胞亚群评价三种宿主抗性模型，所选模型取决于特定靶细胞。已经在耗尽⑶ 4+或⑶ 8+细胞的小鼠中完成了两次PYB 6肿瘤攻击。正如预期的那样，在CD8耗尽后，没有观察到PYB 6肿瘤的频率或潜伏期的显著差异。令人惊讶的是，在CD4耗尽后，没有观察到PYB 6肿瘤的频率或潜伏期的显著差异。相反，CD4+细胞的耗竭对约氏疟原虫感染后寄生红细胞的清除有显著影响。正在研究单核细胞增生李斯特菌攻击后CD4和CD8细胞耗竭的影响。 确定可能对免疫系统造成伤害的化学品具有相当大的公共卫生意义，因为免疫功能的改变可导致超敏反应性疾病、自身免疫性疾病或传染性疾病或肿瘤的发病率增加。在过去15年中，使用标准化测试小组收集的实验动物数据提供了一个数据库，从该数据库中评估了通常用于筛选化学品免疫毒性的各种测试的灵敏度和可预测性。这些结果已被用作免疫毒性风险评估的指南，并已成为许多监管活动的基础。1998年4月，在NIEHS举办了一次研讨会，以确定研究设计，确定扩展组织病理学作为免疫毒性指标的灵敏度和可预测性，并与国家毒理学计划的功能测试组合进行比较。为10种化学品生成标准化载玻片集，这些化学品先前已使用功能测试对其免疫毒性进行了评价。切片的组织学评价已完成，数据已纳入数据库。NIOSH的Michael Kashon博士正在研究病理学家之间的相关性。数据表明，对于大多数结局，病理学家之间存在良好的一致性。然而，即使对于具有良好一致性的变量，也有一些证据表明病理学家之间存在不一致性。对每位病理学家的评分进行直接比较表明，即使在一致性良好的情况下，某些人往往更保守，而其他人则更能够辨别出细微的变化。其他分析检查了病理学家的一致性？的评级在一个单一的组织，通过调查在同一组织类型的所有措施之间的相关性。当来自所有病理学家的数据组合时，四种组织中的每一种的测量值似乎与来自该组织的其他测量值高度相关。然而，当独立检查每位病理学家的相关性时，仅胸腺评价保持相同的高度相关性。对于脾脏、骨髓和淋巴结测量，每位病理学家的结果相关性较差，这引起了对病理学家在这些组织中的每种不同测量中的评级一致性的担忧。报告这些调查结果的手稿正在编写中。

Studies being conducted as part of an interagency agreement between NIEHS and FDA as part of the NIEHS AIDS effort are determining the relationship between decrements in immune cell phenotypes and susceptibility to infection or tumors. Studies conducted in the laboratory of Dr. James Weaver at FDA, using monoclonal antibodies (Moabs) against CD4 and CD8, to establish titration curves for the depletion of these cell subpopulations in B6C3F1 mice have been completed. At NIEHS, we are examining the effects of cell depletion in specific host resistance models. These models include infection using bacteria (Listeria monocytogenes or Streptococcus pnuemoniae), an intracellular parasite (Plasmodium yoelii) or virus (Influenza) and a tumor challenge (PYB6 or B16F10). Three host resistance models will be evaluated for each cell subpopulation, with the selected model dependent on the specific target cell. Two PYB6 tumor challenges have been completed in mice depleted of CD4+ or CD8+ cells. As expected, no significant differences were observed in frequency or latency of PYB6 tumors following CD8 depletion. Surprisingly, no significant differences were observed in frequency or latency of PYB6 tumors following CD4 depletion. In contrast, depletion of CD4+ cells had significant effects on clearance of parasitized erythrocytes following infection with Plasmodium yoelii. Studies examining the effects of CD4 and CD8 cell depletion following challenge with Listeria monocytogenes are in progress. The identification of chemicals that have the potential to cause injury to the immune system is of considerable public health significance, as alterations in immune function can lead to increased incidence of hypersensitivity disorders, autoimmune or infectious diseases or neoplasias. Experimental animal data collected over the past 15 years using standardized testing panels has provided a database from which the sensitivity and predictability of a variety of tests commonly used for the screening of chemicals for immunotoxicity has been evaluated. These results have been used as guidelines for risk assessment in immunotoxicity and have been the basis for a number of regulatory activities. In April 1998 a Workshop was held at NIEHS to establish study design to determine the sensitivity and predictability of extended histopathology as an indicator of immunotoxicity as compared with the National Toxicology Program's functional testing battery. Standardized slide sets were generated for 10 chemicals, which had previously been evaluated for their immunotoxicity using functional tests. The histological evaluation of the slides has been completed and the data has been incorporated into a database. Dr. Michael Kashon at NIOSH is examining the correlation between the pathologists for the endpoints examined. The data indicate that for a majority of the outcomes, there was good agreement between the pathologists. However, even for variables with excellent agreement there was some evidence of inconsistency between pathologists. A direct comparison of the ratings for each pathologist indicates that, even where there was good agreement, certain individuals tended to be more conservative while others were more able to discern subtle changes than others. Additional analyses examined the consistency of a pathologist?s ratings in a single tissue by investigating the correlation among all the measures in the same tissue type. When data from all pathologists were combined, measures in each of the fou r tissues seemed highly correlated with the other measures from that tissue. However, when correlations were examined for each pathologist independently, only the thymus evaluations maintained the same high degree of correlation. For spleen, bone marrow and lymph node measures, the outcomes for each pathologist were less well correlated, raising concern about the consistency of a pathologist's ratings across different measure s in each of these tissues. A manuscript reporting these findings is in preparation.