The effects of RES 'blockade' on antibody formation. IV. Inhibition of plaque-forming cells in spleen cultures treated with carbon particles.

The effects of colloidal carbon particles on induction of antibody-forming cells in tissue-culture suspensions of spleen cells from normal or sheep erythrocyte primed donor mice were determined. Addition of carbon to normal spleen-cell cultures prevented induction of the primary' type immune response . The time at which the carbon was added to the cultures was important, since less suppression occurred when carbon treatment was delayed 48 hours after initiation of culture. Furthermore, the most suppression occurred with the largest dose of carbon used. Injection of normal donor mice with carbon at various time intervals prior to death interfered with the ability of the spleen-cell suspensions to respond to sheep erythrocytes by formation of antibody plaques. Maximum suppression occurred when the donor mice were treated with carbon 1–2 days before they were killed. The anamnestic antibody plaque response was also suppressed by addition of carbon particles to spleen-cell cultures derived from mice primed with sheep erythrocytes several weeks before they were killed. There was a greater suppression of the 7S than 19S PFC response . However, the only marked suppression occurred when the highest dose of carbon was used and when it was added to the cultures at 0' time. Direct injection of carbon into mice primed with sheep erythrocytes 3–4 weeks previously also interfered with the secondary response of the spleen-cell cultures . Both 19S and 7S antibody-forming cells were suppressed, with a greater suppression of 7S PFCs. The results of these experiments were interpreted as indicating that phagocytic cells, capable of being `blockaded' or by carbon suspensions, are necessary for induction of both primary and secondary type antibody plaque responses . It seems likely that the carbon particles compete with the red blood cell antigens for a limited number of antigen-processing cells.