Intestinal absorption of colostral lymphoid cells in newborn piglets

Intestinal absorption of colostral lymphoid cells was studied in 23 piglets of four sows (sows A, B, C and D). From the colostrum and blood of the sows the lymphoid cells were isolated with Ficoll-Paque and labelled with technetium (Na99mTcO4). In the 7th hour after birth, 5-ml volumes of the cell suspensions were injected, following laparotomy, directly into the stomach (piglets of sow A) or into the jejunum (piglets of sow B), whereas piglets of sows C and D received the suspensions through a naso-oesophageal tube. Cryostat sections of duodenum, jejunum and lymph node samples of piglets killed by bleeding 8 h after the treatment were examined by autoradiography. It was found that lymphoid cells present in the colostrum of a piglet's own mother were absorbed from the digestive tract and, via the lymphatic vessels, were transported to the mesenteric lymph nodes. Electron microscopy revealed that absorption took place intercellularly. Colostral cells of sows other than a piglet's own mother were observed only in the epithelial layer of the mucous membrane. The lymphoid cells isolated from the sows' blood and heat-treated colostral lymphoid cells were not absorbed. The results indicate that in the pig, an animal having an epitheliochorial placenta, the colostral lymphoid cells are absorbed from the digestive tract and, hence, they can confer an active cellular immunity on the newborn piglets.