“…As there was no significant difference in age between the two groups in this study and as no animals were less than 2 years of age, age is not likely to have contributed to the findings. 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.…”