MALT structure and function in farm animals

Abstract

-Mucosa-associated lymphoid tissue (MALT) is defined as an organized lymphoid tissue in the mucosa that samples antigens. The morphological characteristics that distinguish MALT from lymphoid infiltrates are discussed. MALT has been extensively investigated in laboratory animals, while knowledge in cattle, sheep, goats, pigs and horses that are summarized under the term farm animals in this review is fragmentary. Literature data about the distribution, morphology, function and involvement in infectious diseases of MALT in farm animals are described. The understanding of specific features of MALT in other species than laboratory animals is important for comparative research, in order to understand pathological and immunological processes in the respective species and as a potential route of vaccination of mucosal surfaces.

Examination of the Reticular Epithelium of the Bovine Pharyngeal Tonsil

“…This complex of lymphoid elements, located at the junction of the nasopharynx and oropharynx, is well positioned to sample antigens entering through either the oral cavity or nasal cavity (Kraehenbuhl and Neutra, 2000;Nave et al, 2001;Liebler-Tenorio and Pabst, 2006). Indeed in ruminants, tonsils represent an important component of the respiratory tract associated lymphoid tissue (RTALT) (Chen et al, 1989;Chen et al, 1991) and share morphological and functional characteristics of mucosa associated lymphoid tissue (MALT), such as Peyer's patches; one being antigen processing (Liebler-Tenorio and Pabst, 2006). Unlike lymph nodes, tonsils do not possess afferent lymphatic vessels (Saar and Getty, 1975); the significance of which is that foreign antigens interact directly with tonsils without prior processing.…”

“…In bovine tuberculosis (Cassidy et al, 1999), and bovine spongiform encephalopathy (BSE; Wells et al, 2005) tonsils may serve as a port of entry for pathogens. Ruminants have less extensive RTALT than other species and the pharyngeal tonsil has been described as the major component of RTALT in cattle and sheep (Anderson et al, 1986;Chen et al, 1989;Schuh and Oliphant, 1992;Liebler-Tenorio and Pabst, 2006). Descriptions of microscopic, ultrastructural, and immunohistochemical features of the ovine and bovine pharyngeal tonsil have added to our understanding of this important tissue (Casteleyn et al, 2010;Breugelmans et al, 2011).…”

Locations of gut-associated lymphoid tissue in the 3-month-old chicken: a review

“…This review paper presents an overview of the MALT that is located in the avian intestinal tract, the so-called gut-associated lymphoid tissue (GALT) (Lillehoj & Trout, 1996;Liebler-Tenorio & Pabst, 2006). From proximal to distal, the avian intestinal tract contains a pharyngeal tonsil, diffuse lymphoid tissue and lymphoid follicles in the cervical and thoracic parts of the oesophagus, an oesophageal tonsil, diffuse lymphoid tissue in the proventriculus, a pyloric tonsil, Peyer's patches, Meckel's diverticulum, two caecal tonsils, diffuse lymphoid tissue in the rectum, the bursa of Fabricius and diffuse lymphoid tissue in the wall of the proctodeum.…”

Immunohistochemical Analysis of Leucocyte Subsets in the Sinonasal Mucosa of Cats with Upper Respiratory Tract Aspergillosis

“…Inflammatory cell populations within the normal respiratory mucosa also differ between species, in particular the presence or absence of discrete lymphoid tissue aggregates, nasal-associated lymphoid tissue (NALT) and the degree of epithelial expression of MHC class II (Krejci et al, 2013). In healthy dogs, NALT has not been identified and epithelial MHC class II expression is rare (Peeters et al, 2005b), while both of these characteristics are common in horses (Banks et al, 1999;Liebler-Tenorio and Pabst, 2006;Quintana et al, 2011) in the absence of respiratory disease. NALT has been previously reported in cats in the absence of upper respiratory tract disease (Venema et al, 2013).…”