Cell-Mediated Immunoprotection in Calves Immunized with Rough Salmonella Dublin * *This paper was presented in a symposium on Recent Advances in Enterobacteriaceae Research, held in November, 1978, at Haryana Agricultural University, Hissar

SUMMARY Ten calves were immunized with rough Salmonella dublin and exhibited marked cellular immune response and comparatively poor humoral response. The cell-mediated immunity was exhibited by delayed skin hypersensitivity reaction of 10·0 to 14·0 mm skin thickness at 48 h post-antigen inoculation (p. i.), leucocyte migration inhibition of 73·96%; humoral immune response 18·5 to 25·5 mm by immediate skin hypersensitivity reaction at 6 h p. i., H titres 1:400 to 1:3200 and total immunoglobulin levels of 43·0 to 65·0 mg/ml of serum, in calves three weeks post immunization. On challenge with smooth. S. dublin three weeks post immunization, calves exhibited fever, diarrhoea and excreted challenge organisms not beyond one week and became normal thereafter. The calves at the time of challenge neither had high agglutinin titres nor elevated serum immunoglobulin levels, but all of them survived. The control group of calves, besides exhibiting typical symptoms, excreted the challenge organisms until death. These observations provide evidence of a relatively predominant role of cell-mediated immunity in protection of calves against challenge.