Morphological Analysis of Lymph Nodes in Odontocetes From North and Northeast Coast of Brazil

Abstract

The morphology and location of lymph nodes from seven species of Odontocetes, of both sexes and different age groups, were described. All animals were derived from stranding events along the North and Northeastern coasts of Brazil. After the identification of lymph nodes in situ, tissue samples were analyzed for light and electron microscopy. Vascular volume density (VVD) and vascular length density (VLD) were evaluated in the mesenteric lymph nodes. Lymph nodes occurred as solitary nodules or in groups, varying in shape and size. In addition to using the nomenclature recommended by Nomina Anatomica Veterinaria, new nomenclatures were suggested based on the lymph nodes topography. Lymph nodes were covered by a highly vascularized and innervated capsule of dense connective tissue, below which muscle fibers were observed, inconsistently, in all studied species. There was no difference in VLD among different age groups. However, VVD was higher in adults. Lymph nodes parenchyma was divided into an outer cortex, containing lymph nodules and germinal centers; a paracortical region, transition zone with dense lymphoid tissue; and an inner medulla, composed of small irregular cords of lymphatic tissue, blood vessels, and diffuse lymphoid tissue. Abundant collagen fibers were observed around arteries and arterioles. Germinal centers were more evident and developed in calves and young animals, being more discrete and sparse in adults. The morphology of lymph nodes in Odontocetes was typical of that observed in other terrestrial mammals. However, new groups of lymph nodes were described for seven species occurring in the Brazilian coast. Anat Rec, 297:939-948, 2014. V C 2014 Wiley Periodicals, Inc.

Morphology of mucosa-associated lymphoid tissue in odontocetes

“…Smith et al () believe that the location of LT expose cetaceans to an imminent danger in cases of infection or inflammation due to its location in the respiratory tract. However, these researchers, while studying T. truncatus , found no significant change to occlude the airways of animals evaluated, suggesting that the immune response of this lymphoid organ is somehow segregated from the lymph nodes present in this region such as the cervical lymph nodes (Silva et al, ). This was confirmed in the present study, where there was no increase in size of the cervical lymph nodes in any of the animals studied.…”

Aspectos ambientais e infecciosos relacionados à imunossupressão em cetáceos: uma breve revisão

“…Moskov et al (1969) described the lymph nodes of Phocoena phocoena and Delphinus delphis with a central location of the lymphoid follicles, and this arrangement was similar to the inverse architecture described in swine. In other species, the arrangement follows the cortex-medulla pattern, common in most mammals (SILVA et al, 2014).…”

“…It is a secondary lymphoid organ whose parenchyma can be divided into a cortical and a medullary region, covered by a collagen capsule of a dense connective tissue. Between these two regions, there is a deep cortical or paracortical region composed primarily of T lymphocytes and reticular cells, together with a few plasma cells and macrophages (JUNQUEIRA;CARNEIRO, 2008;SILVA et al, 2014). B lymphocytes are the predominant cell type in the cortical region and are organized in spherical or ovoid arrangements designated lymphoid follicles (JUNQUEIRA;CARNEIRO, 2008).…”

“…The medullary region, in turn, contains macrophages, B lymphocytes entangled in lymphatic vessels, blood vessels, and diffuse lymphoid tissue (ROMANO et al, 2002;JUNQUEIRA;CARNEIRO, 2008). Silva et al (2014) described the morphology and location of lymph nodes of seven Odontocetes species: Sotalia guianensis, S. fluviatilis, Stenella clymene, S. longirostris, Inia geoffrensis, Peponocephala electra, and Globicephala macrorhynchus, from the North and Northeast regions of Brazil. The following lymph node types were found according to their location in the organism: parotid, mandibular, hyoid, cervical (superficial and deep), periscapular, mediastinal, hilar respiratory, pulmonary, diaphragmatic, gastric, mesenteric, mesocolic/colic, hilar hepatic, pancreatic, hilar renal, pelvic, and genital (male and female).…”

The Odontocete Ear Canal-Associated Lymphoid Tissue (ECALT) and Lymph Nodes: Morphological and Pathological Description with Immuno-Phenotypic Characterisation

“…There are many homologies between the terrestrial and marine mammal immune system [ 1 ]. As in all mammals, cetaceans possess lymphoid organs that are spatially distributed in strategic locations as part of a first barrier protection mechanism against infection [ 1 , 6 , 7 ]. Aside from nodular lymphoid tissue, several organs possess a mucosa-associated lymphoid tissue (MALT), which is diffusely spread lymphoid tissue along mucosal surfaces, essential in initiating an immune response to extraneous antigens [ 8 ].…”