B-cell tolerance has been induced by oligovalent thymus-dependent antigens in an entirely in vitro system. Dissociated spleen cells from congenitally athymic (nu/nu) mice were preincubated for 24 h with 0.1 -- 1 mg/ml of either fowl gamma globulin (FGG) of DNP-human gamma globulin (DNP-HGG). After washing, the cells were tested for the ability to mount in vitro, thymus-independent responses against FGG and DNP. A state of specific responsiveness to either FGG or DNP was thus demonstrated. Features of this wholly in vitro system that paralleled previous findings on the in vivo induction of B-cell tolerance in nu/nu mice were the kinetics, 24 h being required for tolerance induction in either case, the abrogation of tolerance induction by the presence of POL both in vivo and in vitro, and finally the observation that in neither case was there a requirement for the antigens to be deaggregated. It was shown that DNP-(Fab) 2 fragments prepared from HGG induced DNP-specific tolerance indicating that the Fc piece was not required for tolerance induction in this in vitro system. DNP-bovine serum albumin was less effective than DNP-HGG or DNP-(Fab)2. Preincubation with subtoxic concentrations of DNP-lysine of DNP-epsilon-capric acid had only a marginal effect on DNP responsiveness. Since nu/nu mice, lacking in detectable T-cell function, were used as spleen cell donors, this work provides further evidence that B-cell tolerance to thymus-dependent antigens can be induced without the participation of T cells. It is suggested that B-cell tolerance to thymus-dependent antigens occurs when the antigen in a sufficient concentration and over a sufficient period of time has direct access to the B cell. This contact with antigen must be in the absence of an additional influence provided either by adjuvants like endotoxin or POL, or by activated macrophages, which may be stimulated by activated T cells; otherwise not tolerance but B-cell activation will occur.

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