ABSTRACT
This chapter focuses on relevant molecular and cellular biology aspects of the lymphoid system, to aid pathologists in understanding the pathobiologic implications of xenobiotic-induced changes. It discusses intended to assist anatomic pathologists in the identification and categorization of changes to the immune system using rigorous histopathologic examination of lymphoid organs accompanied by integration of clinical pathology and organ weight data. However, in nonclinical safety assessment, direct and indirect alterations of the thymus in laboratory species remain a reasonable indicator of possible systemic effects on the immune system. Splenic weight, especially relative to brain, is an important component in the analysis for immunotoxicity; decreased spleen weight has been found to be a reliable indicator of systemic immunotoxicity in rodents, especially when combined with histomorphology. The reticular cells and associated fibers along with macrophages make up the splenic cords that provide the filtration function of the spleen by trapping effete RBCs and blood-borne particulates.
