The crop may be an important site along the upper alimentary tract in which a humoral immune response against Salmonella Enteritidis (SE) is elicited locally. The mucosal immune response within the crop (ingluvies) of specific-pathogen-free (SPF) white leghorn (WL) chickens against SE was investigated. Three trials were conducted using SPF WL pullets at age 5–6 wk. Trial 1 consisted of 77 birds evaluated for 10 wk post-SE infection (pi), trial 2 was composed of 72 birds monitored through 8 wk pi, and trial 3 was made up of 30 birds assessed for 5 wk pi. Birds were challenged per os with 108 colony-forming units/ml SE phage type 13. Crop lavage samples, crop tissues, ceca, and/or liver-spleen were collected preinfection and then at weekly intervals post-SE infection. Bacteriologic examination of cecal contents and/or liver-spleen occurred weekly to monitor progression of SE infection. Crop lavages were analyzed for SE-lipopolysaccharide (LPS)-specific immunoglobulin A (IgA) by enzyme-linked immunosorbent assay to assess humoral immune response. General histologic staining (hematoxylin and eosin [H&E] and methyl green-pyronin [MGP]) and immunohistochemical (IHC) staining (monoclonal antibodies CD45 and Bu-1) were applied to serial sections of crop to evaluate lymphoid tissue via light microscopy, to grade isolated lymphoid follicles (ILFs) by using score 0 (minimal, <50 µm in diameter) to score 5 (sizable, >200 µm in diameter) scale, and to characterize the cellular population of ILFs. Results revealed that cecum samples and liver-spleen samples were 100% SE culture positive at 1 wk pi, and then the percentage of SE positives progressively declined over time. Markedly increased crop SE-LPS-specific IgA antibodies were detected in crop samples by 2–3 wk pi, and the humoral response remained elevated above week 0 baseline for the duration of each trial. Crop ILFs of score 3 to 5 were observed in H&E-stained tissues, with an increased proportion of ILFs in post-SE–infected crops vs. uninfected. MGP staining showed plasma cells scattered within and at the periphery of ILFs. IHC staining revealed CD45 (pan-leukocyte) and Bu-1 (B-lymphocyte)–positive cells within crop ILFs. The chicken crop seems to be an organ in which lymphoid tissue may arise in response to enteric SE infection, and a site in which a humoral response may be generated against the SE pathogen.
Abbreviations: ANOVA = analysis of variance; AP = alkaline phosphatase; BG = brilliant green agar; CFU = colony-forming units; DAB = diaminobenzidine; ELISA = enzyme-linked immunosorbent assay; GALT = gut-associated lymphoid tissue; H&E = hematoxylin and eosin; HRP = horseradish peroxidase; Ig = immunoglobulin; IHC = immunohistochemistry/immunohistochemical; ILF = isolated lymphoid follicle; LPS = lipopolysaccharide; MGP = methyl green-pyronin; NA = nalidixic acid; nalR = nalidixic-acid resistant; NB = novobiocin; OD = optical density; PBS = phosphate-buffered saline; PP = Peyer's patch; PT13 = phage type 13; PBS = phosphate-buffered saline; pi = postinfection; RV = Rappaport-Vassiliadis; SE = Salmonella Enteritidis; SEPRL = Southeast Poultry Research Laboratory; SPF = specific-pathogen-free; TBS = Tris-buffered saline; TSB = tryptic soy broth; WL = white leghorn
Evaluación celular del tejido linfoide del buche de aves leghorn blancas libres de patógenos específicos.
El buche es un sitio importante del tracto digestivo superior donde la respuesta inmune humoral contra Salmonella Enteritidis se estimula localmente. En este estudio se investigó la respuesta inmune mucosal dentro del buche de aves leghorn blancas libres de patógenos específicos (SPF, por su sigla en inglés). Tres ensayos fueron llevados a cabo usando pollonas leghorn blancas SPF de 5–6 seman