Factors influencing the secondary immune response in rabbits to Salmonella typhosa.

The characteristics of the primary response, as well as those of the secondary response, to different doses of Salmonella typhosa when elicited at two different time intervals were analysed. The antibody response demonstrates that the size of the primary dose, and the size of the secondary dose, have significant effect on the subsequent synthesis of the secondary IgM and IgG antibody response to both 'H' and 'O' antigens. The time elapsed between the primary and secondary response tends to decrease the IgG response. Due to the high immunogenicity of the 'H' antigen the maximum IgG levels were reached within the range of doses used. These high levels of antibody inhibited the secondary IgM response by a feedback mechanism. Enhanced or equivalent response of predominant anti 'O' IgM system was recorded.