Intestinal absorption of colostral lymphocytes in newborn lambs and their role in the development of immune status.

ABSTRACT

Two model experiments were conducted to study the intestinal absorption of colostral lymphoid cells and the role of these cells in the development of immune status in newborn lambs. In experiment I, 17 lambs of 14 Merino ewes were used. Suspensions of lymphoid cells separated from the colostrum (cell density 5 x 10(6)/ml) and blood (3 x 10(6)/ml) were labelled with technetium (Na99mTcO4) of 37 MBq/ml radioactive concentration. In three groups of lambs, 10-ml volumes of the cell suspensions were injected directly into the duodenum after laparotomy, while in a fourth group (group Ia) the same volume was administered to the animals through an oesophageal tube. The labelled cells revealed that colostral cells of the lamb's own dam are absorbed from the gastrointestinal tract and get into the newborn lamb's lymph circulation irrespective of the route of application. In experiment II, involving 40 lambs of 40 ewes, we studied the effect of absorbed colostral lymphocytes on the development of the newborn lamb's immune status. Twenty ewes (group A) each were treated with 3 ml tetanus anatoxin twice, while the remaining animals (group B) were left uninoculated. Lambs of group A (designated A2) were separated from their dams immediately after birth, then were administered, through an oesophageal tube, 10 ml of a suspension of lymphoid cells (cell density 5 x 10(6)/ml) separated from the maternal colostrum. Subsequently, the lambs were interchanged with lambs of nonimmunized ewes of group B (designated lambs B1), i.e. were mutually put out to nursing. At three days of age, lambs of groups A1, A2, B1 and B2 were inoculated with 3 ml tetanus anatoxin, then blood samples were taken from them 5 times in a period of 27 days for comparative examination of the humoral and cellular immune reactions. The results demonstrate that lymphoid cells from the colostrum of the lambs' own dam become absorbed into the newborn lambs' lymph circulation, remain immunologically active and may transfer, besides immunological memory, also cellular activity.