Secretory immune response in intestinal mucosa and salivary gland after experimental infection of pigs with transmissible gastroenteritis virus.

Pigs 8 to 10 weeks of age were orally infected with transmissible gastroenteritis (TGE) virus or infected by inoculation of the virus into Thirty-Vella loops of jejunum. Concentrations of immunoglobulin (Ig) A, IgM, and IgG in serum, saliva, jejunal secretions, loop secretions, and bile were determined by solid-phase radioimmunoassay for TGE virus-infected and control pigs. A multiple-staining fluorescent antibody technique was used to determine the relative numbers of IgA-, IgM-, and IgG-producing plasma cells in intestinal mucosa, mesenteric lymph node, spleen, iliac lymph node, and submandibular salivary gland. The numbers of IgA- and IgM-producing plasma cells were greater in the jejunal mucosa of pigs infected and reinfected orally with TGE virus than in that of the control pigs. There was also an increase of IgA- and probably of IgM-cells in the submandibular salivary glands. Similar numerical increases of IgA- and IgM-cells were observed in jejunal mucosa and salivary glands of all pigs with intestinal loops whether exposed to TGE virus or not. Increases in plasma cells in mucosa or salivary gland were not associated with increases in concentrations of IgA or IgM in the respective secretions or serum. The data support the hypothesis that after stimulation, IgA- and IgM-producing cells leave the intestinal mucosa and are trapped by distant secretory epithelial. The absence of a simultaneous increased concentration of IgA and IgM in saliva and intestinal secretions indicates that in an intact epithelium, the transport of IgA and IgM mediated by secretory component is probably saturable.