IMMUNOHISTOCHEMICAL DETECTION OF CD25+LYMPHOCYTES IN FELINE INJECTION SITE SARCOMA AND POST-INJECTION PANNICULITIS

INTRODUCTION: CD25 (IL-2Ra) is the α-subunit of the membrane-bound interleukin-2 receptor (IL-2R), which is mainly expressed by regulatory T cells (Tregs). Tregs play a pivotal role in the homeostasis of the immune system and in the modulation of the immune response (1,2). Two type of Tregs are known: natural Treg and adaptive Treg. Normally these cells regulate immune system activity and prevent autoimmunity. Imbalanced function or number of these cells, either enhanced or decreased, might lead to tumor development and autoimmunity, respectively (1,2,3,4). In the present study we hypothesized the presence of CD25+ cells among tumor infiltrating lymphocytes (TILs) that are normally associated with feline injection-site sarcoma (FISS), a type of tumor considered a good model to study a link between inflammation and neoplasia. To this end the CD25 protein expression levels were analyzed by immunohistochemistry in eighteen cases of FISS and in 15 cases of post-injection panniculitis (PIP).