Differential cytochemical staining characteristics of channel catfish leukocytes identify cell populations in lymphoid organs

This is one of the first characterizations of channel catfish (Ictalurus pu nctatus) leukocytes by enzyme cytochemistry. Leukocytes demonstrated cytopl asmic staining patterns very similar to mammalian leukocytes when stained w ith acid phosphatase, alpha-naphthyl butyrate esterase, beta-glucuronidase, alpha-naphthyl acetate esterase, Sudan Black B and anti-immunoglobulin spe cific immunohistochemistry. Lymphocytes, monocytes, macrophages, neutrophil s, and surface immunoglobulin positive (surface Ig+) cells were present in channel catfish renal hematopoietic tissue and spleen and demonstrated dist inctive cytoplasmic foci staining patterns, cytoplasmic blushing or cell me mbrane staining. Monocytes, macrophages, lymphocytes and surface Ig+ cells were present in the thymus. Thymic and splenic cellular organization appear ed very similar to these same mammalian tissues. In the thymus, acid phosph atase positive cells were distributed throughout the parenchyma, while alph a-naphthyl butyrate esterase and beta-,glucuronidase positive cells were co ncentrated in the cortex and the medulla, respectively. Surface immunoglobu lin positive cells occurred in the cortex. In the spleen, acid phosphatase positive cells were scattered throughout the parenchyma, while alpha-naphth yl butyrate esterase positive cells were scattered throughout the parenchym a and adjacent to splenic arterioles. beta-glucuronidase and surface immuno globulin positive cells were restricted to immediately adjacent to splenic arterioles. Sudan Black B positive cells were scattered throughout the pare nchyma, while alpha-naphthyl acetate esterase positive cells occurred adjac ent to peri-arteriole lymphoid sheaths and appear very similar to mammalian metallophils. (C) 2000 Elsevier Science B.V. All rights reserved.