Influence of route and dose of antigen on the migration inhibition and plaque-forming cell responses to sheep erythrocytes in the lizard, Calotes versicolor.

The influence of route of administration and dose of antigen on the generation of humoral and cell-mediated immune (CMI) responses has been studied in the lizard, . Intramuscular (i.m.) immunization was found to be more suitable for the induction of both plaque-forming cell (PFC) and migration inhibition (MI) responses to sheep erythrocytes (SRBC) than the intraperitoneal (i.p.) route. The i.m. route favoured the development of quicker PFC as well as MI responses. The latter was observed to be sustained up to a month after immunization. In contrast, with the i.p. route of immunization, the peak PFC and MI responses appeared slowly and were followed by a sudden decline. An inverse relationship between PFC and MI functions was noted. The maximum level of MI was obtained with 10 SRBC while the PFC response was greater with the higher doses of antigen. Low dose of antigen induced a strong and quick MI response with concomitant postponement of the PFC response. Incorporation of SRBC into Freund's complete adjuvant did not influence the MI level. After an injection of a supra-optimal dose of SRBC, the MI level was very low at a time when the PFC response was at its maximum and the degree of MI rose again after the decline in PFC number. Thus, the induction of antibody synthesis needs a higher threshold level of antigen for its full expression, in contrast to the minimal antigen dose required for MI response to SRBC in lizards.