The present study was conducted to evaluate concentration dependent immune response of Streptococcus equi in laboratory rabbits to gauge the immunogenic potential of Streptococcus equi for the development of future vaccine against strangles in equines. Streptococcus equi the causative agent of Strangles in young foals was isolated from the pus of submandibular abscess of strangles affected foals. Streptococcus equi was characterized on the basis of morphological, cultural and biochemical on 5% horse serum Sodium azide blood agar base and by Prolax streptococcal latex system and Analytical Profile Index (API) System. Three concentrations of formalized Streptococcus equi @ 4 × 107, 4 × 109 and 4 × 1011 were inoculated in four groups, one group as control negative, each group containing four adult male laboratory rabbits and sera of the inoculated rabbits were subjected to Indirect Heamagglutination Assay by using M-Protein of Streptococcus equi as antigen. It was found that the rabbits which were given concentration of Streptococcus equi @ 4 × 109 and 4 × 1011 cells per ml showed the highest Indirect Heamagglutination (IHA) antibody titres with GMT as 16.0.