Antibody Induction and Tolerance

Cellular events in the immune response : analysis and in vitro response of mouse spleen cell populations separated by differential flotation in albumin gradients

Cell suspensions from the spleens of normal mice or mice injected with sheep erythrocytes were separated on a discontinous bovine serum albumin density gradient. Four bands or subpopulations were obtained and were assayed for antibody-forming cells, and for antigen-sensitive precursor cells. The antibody-forming cells were assayed by the hemolytic plaque assay and the antigen-sensitive precursors were assayed by the number of plaque-forming cells which developed after 3 or 5 day's culture with antigen. It was found that both antibody-forming cells and their precursors were present in the denser region of the gradient when spleen cell suspensions were taken from unimmunized mice. In contrast, both antibody-forming cells and precursors floated to the top in cell suspensions from mice sacrificed 1, 2, or 3 days after antigen injection. The change in density was detectable as early as 12 hr and was complete by 18 hr. The cell which changed in density was specific for the antigen that brought about that change. The significance of these findings is discussed.

Distribution of antibody-forming cells of different specificities in the lymph nodes and spleens of guinea pigs

The distribution of antibody-forming cells of different specificities in the lymph nodes and spleens of guinea pigs immunized with two separate antigens or with antigens bearing two determinants was studied. When animals were immunized with two soluble protein antigens or antigens in which the two antigenic determinants were on the same molecule, antibody-forming cells of different specificities were always randomly intermixed. However, when animals were immunized with two heat-aggregated particulate protein antigens and then boosted with soluble protein antigens, cells of different specificities were often seen to occur in groups. These results suggest that antibody-forming cells may not arise by the antigen-stimulated proliferation of precommitted antibody-forming cells, but rather antibody-forming cells arise by a transformation of uncommitted precursor cells as the result of their interactions with a locally produced material derived from the processing of antigen.

Cell populations and cell proliferation in the in vitro response of normal mouse spleen to heterologous erythrocytes. Analysis by the hot pulse technique

The role of proliferation in the development of 19S antibody-forming cells in the primary response has been investigated in an in vitro system. Spleen cell suspensions from normal, unimmunized mice were cultured in vitro in the presence of mammalian erythrocytes and the number of 19S hemolytic plaque-forming cells that arose 4 days later was measured. The hot pulse technique for the selective irradiation of those cells which synthesize DNA during a defined period of time has been described. The effect of such hot pulses administered at various times after the addition of antigen on the subsequent appearance of antibody-forming cells was determined. The results established that: (a) the onset of DNA synthesis does not start for approximately 24-32 hr after the addition of antigen, (b) essentially all the antibody-forming cells arise by cell division, and (c) different cell populations are involved in the response to two non-cross-reacting antigens.

On the mechanism of antibody synthesis: a species comparison of L-chains

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The functions of the thymus system and the bursa system in the chicken

The bursa of Fabricius and the thymus are "central lymphoid organs" in the chicken, essential to the ontogenetic development of adaptive immunity in that species. Surgical removal of one or both of these organs in the newly hatched chicken, followed by sublethal X-irradiation the next day, has permitted recognition of two morphologically distinct cell systems in the "peripheral lymphoid tissues" of the spleen, gut, and other organs, and clear definition of the separate functions of each cell system. The thymus-dependent development is represented morphologically by the small lymphocytes of the circulation and the white pulp type of development in the tissues. As in mammals, the thymus-dependent tissues of the chicken are basic to the ontogenesis of cellular immunity: graft versus host reactions, responses of delayed hypersensitivity and homograft rejection; and play a less clearly defined role in the antibody response to at least some antigens. Thymectomized-irradiated chickens are deficient in all these responses, and grow more slowly than any of the other experimental groups. In these animals germinal centers, plasma cells, and capacity for immunoglobulin synthesis remain intact. The bursa-dependent development is represented morphologically by the larger lymphocytes of the germinal centers and the plasma cells, and functionally by the immunoglobulins. Bursectomized-irradiated chickens are agammaglobulinemic and unable to produce detectable antibody despite intense, repeated stimulation with bovine serum albumin and Brucella abortus organisms. The thymus-dependent development in these animals seems to be normal; they have adequate numbers of lymphocytes in the circulation and tissues, are able to reject skin homografts, though more slowly than usual, and to exercise graft versus host reactions. The short life span of these chickens has precluded adequate study of responses of delayed hypersensitivity. There was no evidence of significant impairment of reticuloendothelial function in either the bursectomized-irradiated or the thymectomized-irradiated group, as judged by the clearance of colloidal gold and I(131)-tagged keyhole limpet hemocyanin.

Rabbit 19S antibodies with allotypic specificities of the a-locus group

Activity of bacteriophage T4 neutralizing antiserums obtained 8 days after a primary immunization of rabbits with purified phage T4 is due to antibodies of the 19S (IgM) type. This neutralizing activity could be partially inhibited by treatment with excess antiserum directed against the a-locus group allotypic specificity carried by the whole rabbit serum.