Localization of bacterial antigens in calves inoculated orally with ruminal Bacteroides succinogenes and Selenomonas ruminantium.

Localization of bacteria and bacterial materials was investigated in calves inoculated orally with live organisms of both Bacteroides succinogenes and Selenomonas ruminantium by a immunohistological method using rabbit antiserum against the outer membrane of those organisms and by a scanning electron microscope. The intact organisms of both inoculated bacterial species were detected on the rumen wall and in the lamina propria of the forestomach, and S. ruminantium also in the lymph nodes associated with the rumen. The bacterial materials were observed inside of macrophage-like cells in the lamina propria of the forestomach and of lymphoid cells in the lymph nodes. Number of the cells in the mesenteric lymph nodes was smaller than that of the forestomach associated lymph nodes. The results suggest that the orally inoculated bacteria may act as antigenical stimulant in the mucosa of the forestomach and associated lymph nodes of calves.