Antibody-hapten interactions in vivo in mice and sheep

From 5 min to 5 h after an intravenous injection of one of the haptens, elipson-dinitrophenyl-lysine, 2,4-dinitrophenol (DNP), or procaine, mice that were actively immunised against these haptens held more of the hapten in their plasma than did normal mice. Over the same time interval, mice that had been passively immunised with sheep anti-procaine antisera and then treated with procaine held more procaine in their plasma than did mice treated with normal sheep serum. When procaine or DNP was administered orally or intraperitoneally to sheep with circulating antibody to the hapten, the antibody titre was usually reduced 1 h after dosing but returned to the pre-dosing titre by 24 h. Experiments indicated that the reduction in antibody titre was due to in vivo neutralisation of antibody by the hapten.