Studies on the immunizing capacity of orally administered particulate antigens. II. Production of immunological memory in germ-free mice by orally administered sheep erythrocytes.

A study was perfromed to find out, whether or not the oral administration of sheep erythrocytes results in a general primary immune reaction as well as in effective priming for the secondary response in both conventional and germ-free NMRI mice. Whereas negative results were obtained with conventionally held mice, five oral applications of 0.3 ml of a 60% suspension of sheep erythrocytes to germ-free mice, each dose separated by an interval of 24 hr, resulted in a general primary immune response both at the cellular and humoral levels. When such pretreated mice were given an i.p. injection of 4 times 10(8) sheep erythrocytes as a secondary antigenic stimulus 32 days after the last of the five oral applications, the subsequent response was characterized by the predominant development of 7S hemolysin-producing spleen cells. This evidently indicates that effective priming for the secondary response has taken place by the orally administered antigen.