Immune response in dog 2 effect of dose of antigen on antibody production

The primary antibody response of dogs and rabbits to both 'H' and 'O' antigens of Salmonella typhosa following intravenous injection with a formalin killed vaccine from 2.4 x 10(6) to 2.4 x 10(10) organisms/kg body weight was analysed. The animals were restimulated 80 days later with various vaccine concentrations. The lgM anti-'O' and lgG anti-'H' and 'O' antigens in the dogs, were significantly weaker in both primary and secondary response than the comparable rabbit group. Primary lgM anti-'H' response in the dog was found to be greater, equal, or less than that observed in the rabbit. A closer analysis of the primary response indicated that both animal species show the same latent period and doubling time in respect of anti-'H', and the differences observed are probably the result of the number of progenitor cells stimulated by the antigen. On the other hand the suppressed response of the dog to 'O'-antigen is the result of an overall weaker response of this animal to the antigen. The secondary anti-'H' lgM response was found to be greater than, equal to, or less than the primary response in the same animal. The significant inhibition of this response was observed in those animals which received a high primary dose of antigen.