Cell-mediated immunity to Murine tumor allografts. Increase in the activities of activated thymus-derived cells following in vitro incubation

Maternal alloimmune reactions towards the murine conceptus and graft-versus-host reaction (GVHR). I. Priming for anti-paternal GVHR by gestation

In the H-2 compatible (but minor loci-incompatible) BALB/c-DBA/2 strain combination (both H-2d), intravenous injection of 1.3 X 10(7) BALB/c spleen cells from virgin females into DBA/2 newborn mice less than 18 h old does not result in a significant lethal graft-versus-host reaction (GVHR). A strong GVHR (79% lethal) is induced if the BALB/c donors have been preimmunized to DBA/2. Spleen cells from BALB/c mice pregnant by DBA/2 males are also able to induce a significant, but weaker, GVHR (16% lethal) indicating a cellular priming to paternal antigens by gestation. A significant difference exists between anti-DBA/2 GVH reactivity of spleen cells from primiparous (22% lethal) and multiparous (9% lethal) allopregnant BALB/c mice, indicating that the allogeneic boosters of successive allogestations act more on the target-protective side of immunity than on the target-aggressive one. Sera from allopregnant mice (BALB/c X DBA/2) inhibit the GVHR induced by their own cells, while sera from isopregnant ones (BALB/c X BALB/c) have no effect. Thymectomy performed at 6-wk of age, six weeks before gestation did not significantly modify the maternal reactivity. A similar priming by allogestation in the same strain combination was found for local GVHR (induced in adult F1 hybrids) resulting in higher (+132%, P less than 0.005) stimulation indices and seen to be specific for the paternal strain, the indices induced by the same cells being lower (-35%, P less than 0.05) compared to that induced by cells from virgin BALB/c, when injected into irrelevant F1 hybrids (BALB/c X CBA).

Inhibitory and stimulatory effect of spleen cells from tumour bearing animals on the growth of syngeneic tumour cells

When spleen cells from C3H mice inoculated with a primary spontaneously arisen C3H mammary carcinoma were added to tumour target cells of the same type in vitro, both an inhibitory and a stimulatory effect on target cell growth were seen, when compared with the effect of adding normal syngeneic spleen cells. The inhibitory effect was seen regularly when high concentrations of spleen cells were added, while there was a stimulatory effect when low concentrations were added to the tumour target cells. When transferring spleen cells from tumour bearing mice together with a tumour inoculum to groups of normal syngeneic recipients, the resultant tumour growth was enhanced, as compared with recipients given tumour plus normal spleen cells and those given tumour cells only. It was found that the spleen cells which caused the greastest enhancement in vitro caused the greatest inhibition in vitro. This relationship could be explained by assuming the occurrence in spleens of tumour bearers of a population of reactive cells which when added in high concentrations to tumour target cells in vitro cause inhibition, while they cause stimulation of tumour growth in vivo because of being transferred to recipients in relatively low concentrations.

Role of epitope density in the induction of tolerance and immunity with thymus-independent antigens. III. Interaction of epitope density and receptor avidity

The induction of B cell tolerance to 2,4-dinitrophenyl conjugates of polysaccharide antigens (levan or dextran) was studied in mice primed with keyhole limpet hemocyanin (KLH) or 2,4,6-trinitrophenylated KLH. The relationship of the epitope density of the tolerogen with avidity of B cell receptors (as judged indirectly by a plaque inhibition assay) was investigated. It was found that high avidity precursors (IgG) were tolerized by antigen of much lower epitope density, and at lower concentration, than were low avidity precursors (especially IgM cells). IgA cells were intermediate in behavior. These results suggest that the epitope density effect acts by ensuring a necessary degree and/or energy of antigen binding.