This paper deals with the behavior of adult mouse bone marrow cells placed in tissue culture with or without antigen, and subsequently assessed for immune competence after adoptive transfer into lethally X- irradiated, syngeneic hosts. Attention was focussed on B lymphocytes through using hapten human gamma globulin (HGG) preparations as putative tolerogens in tissue culture, the T-cell-independent antigens DNP-POL and NIP-POL as challenge injections in adoptive hosts, and numbers of hapten-specific PFC in host spleens for the quantitation of immune competence. It was found that the capacity of bone marrow cells to mount an adoptive immune response rose by a factor of about fivefold over 3 days in tissue culture. This rise was completely abolished by the presence in the culture of hapten-HGG conjugates with about one mole of hapten per carrier molecule. The prevention of the emergence of immune competence amongst maturing B cells was termed clonal abortion tolerogenesis. Dose-response studies showed the lowest effective antigen concentration to be between 2.5 times 10- minus 10 and 2.5 times 10- minus 9 M, and a standard concentration of 2.5 times 10- minus 8 M was chosen as producing near maximal effects. The tolerance was antigen-specific and time-dependent, being maximal only when antigen was present continuously as the cultured cells was maturing. It did not depend on the presence of T lymphocytes in marrow, and was not of an "infectious" type. In contrast to tolerogenesis of mature B lymphocytes by high antigen concentrations, it could not be abolished by lipopolysaccharide. We speculate that clonal abortion may be a tolerance mechanism of great physiological significance for self- recognition, and discuss the results in the framework of other recent tolerance models, including those involving receptor blockade and suppressor T cells.

B lymphocytes with receptors specific for the hapten fluorescein (FLU) were prepared from the spleens of mice of various ages. For most experiments, a one-step fractionation procedure based on the adherence of FLU-specific cells to FLU-gelatin was used. For some experiments, a subset of higher FLU-binding capacity was prepared from the FLU-gelatin binding population through the use of the fluorescence-activated cell sorter (FACS). FLU-specific B cells were placed into microculture with either FLU(3.6)-human gamma globulin (FLU(3.6)HGG) or FLU(12)HGG usually for 24 h at 37 degrees C. The tolerogen was then removed and 0.1 μg/ml of a T-independent antigen, FLU-polymerized flagellin, was substituted. 3 days later, cells were harvested from the microcultures and assayed for FLU-specific plaque-forming cells to determine any reduction in clonable hapten-specific B cells which the tolerogenesis treatment might have induced. The results showed that with FLU(3.6)HGG, hapten-specific newborn B cells could be tolerized at 1,000-fold lower tolerogen concentrations than adult splenic B cells of equal antigen-binding capacity. The high-avidity subset was even more susceptible to tolerance induction. Tolerance could be induced within 8 but not within 2 h, and at lower tolerogen concentrations, longer periods of tolerogenesis were required for a given effect. Using a 24-h tolerogenesis phase, 50 percent reduction in clone frequency among newborn FLU-gelatin fractionated cells was achieved at 0.08 μg/ml of FLU(3.6)HGG. Tolerance induction in immature B cells was inhibited by the concomitant presence of a polyclonal B-cell activator, Escherichia coli lipopolysaccharide (LPS) but tolerance once induced, was stable to challenge with LPS. Tolerogenesis was hapten specific. The proportion of tolerizable cells in spleens decreased with increasing age, reaching 50 percent at around 9 days. FLUI(12)HGG proved a more powerful tolerogen than FLU(3.6)HGG. It had an effect on adult cells, 50 percent reduction in clone frequency being noted at around 1 μg/ml. However, and in contrast to results claimed for other T- independent systems, there still was a major difference between immature and mature B cells, the immature cells displaying much greater sensitivity to tolerogenesis.

No abstract