Antibody Response to <i>Escherichia Coli</i> Lipopolysaccharide and Type III Pneumococcal Polysaccharide by Congenitally Thymusless (Nude) Mice

Abstract

Abstract The concept of thymus-dependency of immune responses arose from studies of neonatally thymectomized animals and thymectomized, irradiated, bone marrow-reconstituted adult animals. In addition to an impaired cellular response, these animals exhibit a depressed humoral response to some antigens, such as sheep erythrocytes (SRBC), T-2 bacteriophage and certain serum proteins, but produce a normal humoral response to other antigens, such as ferritin, Salmonella flagellar antigen and MS-2 bacteriophage (1). These results have led to a classification of antigens as either thymus-dependent or thymus-independent. There is some controversy as to whether the concept of a thymus-independent immune response which is based on the responses of thymectomized animals is valid. First, it is possible that the immune response to some antigens matures relatively early in ontogeny and appropriate thymus-derived antigen-reactive cells are seeded out from the thymus before its removal at birth. Second, it has been shown that some thymusderived cells can survive irradiation and that bone marrow preparations used in reconstitution may contain thymus-derived cells (2). Therefore, alleged thymus-independent antigens may merely require fewer thymus-derived cells to produce an immune response. Alternatively, thymus-independent antigens may be able to evoke an immune response by some mechanism which does not require the participation of thymus-derived cells.