Immunohistochemistry and Morphology of Reactive Lesions in Lymph Nodes and Spleen from Rats and Mice

The use of immunohistochemistry with anatomical and systematized classifications of nonneoplastic lesions in hematopoietic pathology of lymph nodes and spleens from rats and mice is described. Polyclonal antisera and monoclonal antibodies to leukocyte and other antigens can be used with frozen or fixed tissue sections to identify changes in cell populations in these tissues in response to tissue injury and aging. A classification for reactive lesions of lymph nodes and spleen is proposed that can be utilized for computerized pathology and toxicology data systems. These classifications are based on a systematized anatomic distribution of the lesions with the aid of immunohistochemistry. The association of some lesions with early leukemia or lymphoma of rats and mice is also discussed.