Histology and histochemical enzyme‐staining patterns of major immune organs in Epinephelus malabaricus

Abstract

The histological architecture of major immune organs in the Malabar grouper Epinephelus malabaricus was investigated. The novel characteristics such as melanomacrophage centres (MMCs) appeared in the thymus and lymphopoietic tissue formed as foci in the head kidney. Leukocyte distribution in organs was identified by enzyme histochemistry. b-glucuronidase (BG) reactive cells in the cortex region of the thymus were botryoidally aggregated. Both acid phosphatase (AcP) and BG reactive cells concentrated within the specialized lymphopoietic foci in the head kidney, suggesting that the foci might be functional. Primitive histological characters of immunity were observed in the spleen. Although leukocyte aggregation was demonstrated in the spleen, additional enzyme histochemistry indicated that the aggregate might not be the equivalent of white pulp found in other vertebrates. The histological evidence did not support intestinal involvement in the immune system: there was no demonstrable gut associated lymphoid tissue. The limited distribution in the cortex and medulla boundary and the condensed format of the lymphocytes suggests a functional role for the MMC in the thymus of E. malabaricus. The MMC appearance in the thymus of a teleost was unusual. # 2005 The Fisheries Society of the British Isles

Uncommon hepatic macrophagic foamy‐cell nodules in Iberian barbel (Luciobarbus bocagei Steindachner, 1864) from the Vizela River (Portugal)

“…In detail, cells within the macrophage aggregates/macrophage centers—often named as pigmented macrophages or as melanomacrophages—of the fish liver stained positive for: lipofuscin (commonly accepted as the most prevalent pigment in fish melanomacrophage centers) (Agius & Roberts, ), melanin (Jordanova et al, ; Meseguer, López‐Ruiz, & Esteban, ), ferric compounds/hemosiderin (Leknes, ; Meseguer et al, ), and even copper, principally in older fish (Bunton, Baksi, George, & Frazier, ). Despite we could not find in the literature results of the use of the tetrazonium reaction for staining fish melanomacrophages, positive protein staining can be explainable by the high content of those cells in lysosomal enzymes, such as phosphatases, as demonstrated in liver (Meseguer et al, ) and other organs (Lin, Lin, & Yang, ). Also, basic protein aggregates, along with neutral mucopolysaccharides, were identified in melanomacrophage centers of the goldfish ( Carassius auratus ) peripheral lymphoid organs (Herráez & Zapata, ).…”

A comparison of the expression of immunity-related rag 1 and ikaros genes with histogenesis of the thymus in Epinephelus malabaricus (Bloch & Schneider)

“…In S. quinqueradiata , for example, although the thymus–blood barrier was observed at approximately 45 dpf (similar to Malabar grouper in this study), lobules were not seen until the age of 3 months (Chantanachookhin et al 1991). Melanomacrophage centres have been observed in the thymus of 1‐year‐old E. malabaricus (Lin, Lin & Yang 2004). In the present study, melanomacrophage centres were observed first in the spleen at interval 3‐6 (41 dpf, data not shown), but not observed in thymus until the end of the study.…”

Tolerance of whitefish embryos to Pseudomonas fluorescens linked to genetic and maternal effects, and reduced by previous exposure

“…Previous studies on the ontogeny of the immune system have mainly focused on morphological and histochemical/cytochemical features [8,[11][12][13][14][15][16], whereas the effectiveness of the fish immune system at early developmental stages has rarely been tested experimentally. Numerous infection studies concerning the potential of the immune system have been carried out in juvenile and adult fish [17][18][19][20][21][22][23][24][25][26].…”