Induction of low zone tolerance to sheep erythrocytes in the lizard, Calotes versicolor

Abstract

Adult lizards pretreated with subimmunogenic doses of sheep erythrocytes (SRBC) and subsequently challenged with an optimal dose of SRBC became tolerant to SRBC. In treated lizards the number of plaque-forming cells (PFC) in the spleen and serum antibody level were reduced to 10% of the response in non-treated control lizards. This low level of response was due to true induction of tolerance and not simply to a delay in the occurrence of peak response. Increase in the challenge dose of SRBC did not alter the tolerant state. A minimum period of 3 days was found necessary for the establishment of tolerance. The induced tolerance was antigen specific and persisted for at least 42 days. We discuss the likelihood that this unresponsiveness is similar to low zone tolerance (LZT) previously reported in other animal species.