On the role of histamine receptors in regulating pigmentary responses in Oreochromis mossambicus melanophores

Infection of endemic chub Squalius tenellus with the intestinal tapeworm Caryophyllaeus brachycollis (Cestoda): histopathology and ultrastructural surveys

The endemic chub Squalius tenellus (Heckel, 1843) was introduced more than 100 years ago to Lake Blidinje (Bosnia-Herzegovina). Only 1 species of enteric helminth was found in a sample of 35 chubs, the tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953). The paper includes histopathological investigation with identification of innate immune cells involved in host reaction and molecular data allowed correct designation of the cestode species. Of 35 specimens of chub examined, 21 (60%) harboured individuals of C. brachycollis and a total of 1619 tapeworms were counted, the intensity of infection ranged from 1 to 390 worms per fish (46.2 ± 15.3, mean ± s.e.). Histopathological and ultrastructural investigations showed strict contact between the worm's body and the epithelia and increase in the number of mucous cells, rodlet cells among the epithelial cells. Within the tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were noticed. This is the first study of the occurrence of C. brachycollis in chub from Lake Blidinje and on the response of the innate immune cells of S. tenellus to this tapeworm. Interestingly, in 3 very heavily infected chubs, perforation of the intestinal wall was documented; this is uncommon among cestodes which use fish as a definitive host.

Role of histamine in the regulation of intestinal immunity in fish

In mammals, during the acute inflammatory response, the complex interrelationship and cross-talk among histamine and the immune system has been fairly well characterized. There is a substantial body of information on its structure, metabolism, receptors, signal transduction, physiologic and pathologic effects. However, for early vertebrates, there is little such knowledge. In the case of teleost fish, this lack of knowledge has been due to the widely held belief that histamine is not present in this phylogenetic group. However, it has been recently demonstrated, that granules of mast cells in perciforms contain biologically active histamine. More importantly, the inflammatory response was clearly demonstrated to be regulated by the direct action of histamine on professional phagocytes. Nevertheless, the molecular basis and exact role of this biogenic amine in perciforms is still a matter of speculation. Therefore, this review intends to summarize recent experimental evidence regarding fish mast cells and correlate the same with their mammalian counterparts to establish the possible role of histamine in the fish intestinal inflammatory response.