Immunological histopathology of American kestrels (Falco sparverius) exposed to the flame retardant isopropyl triphenyl phosphate

This work is part of a study of the immunological effects of exposure to alternative flame retardants in avian species. For the pathology portion of the study, hatchling American kestrels (Falco sparverius) were exposed to the flame retardant isopropyl triphenyl phosphate (ITP) and then challenged with a synthetic analogue of viral double-stranded RNA, polyinosinic:polycytidylic acid (poly I:C). Control birds were challenged with vehicle only or vehicle and poly I:C. At euthanasia, spleen, thymus, and bursa of Fabricius were collected and fixed in 10% neutral buffered formalin for histopathological assessment. Slides were processed and stained with hematoxalin and eosin as per standard procedure (Luna 1968). Quantitative and qualitative B and T cell parameters were assessed by light microscopy. Specifically, variables assessed included the following: spleen: proportion of white to red pulp; thickness of peri-arteriolar lymphoid sheaths; number and diameter of lymphoid follicles; thymus: total area; area of medulla; density of cortical lymphocytes; number of tingible body macrophages; heterophil infiltration; bursa: follicular and medullary area; cellular density; apoptosis; heterophil infiltration; presence of follicular cysts. Evaluation of the architecture and cellular population of immune organs will shed light on potential functional immunological effects of exposure that may lead to increased susceptibility to infectious disease. (Luna LG. 1968. Manual of histologic staining methods of the armed forces institute of pathology, 3rd edn. McGraw-Hill, New York, NY.)