The effect of the immunomodulator corynebacterium parvum on hemisplenectomized mice.

The immunomodulator Corynebacterium parvum stimulates the reticuloendothelial system and causes splenic hypertrophy. The ability of C parvum to stimulate splenic regeneration in hemisplenectomized mice and decrease susceptibility to intranasal pneumococcal challenge was studied. Mice were divided into two groups, control sham-operated (n = 48) and hemisplenectomized (n = 47) animals. Ten days later, each group was divided into two subgroups, those injected with C parvum (700 mcg IVP) and those injected with an equivalent volume of saline. The animals were challenged with Streptococcus pneumoniae, which was injected into one nostril three weeks postoperatively, and mortality was assessed. Four and one-half weeks postoperatively, splenic tissue was removed, measured, weighed, and submitted for histologic examination. The number of spleen cells per gram of tissue was assessed. Treatment with C parvum resulted in a significant increase in the splenic weight in both hemisplenectomized and control animals compared to similar saline-injected mice (P less than 0.001). The percentage increase in spleen weight of hemisplenectomized mice (106%) was significantly greater than that for control animals (56%; P less than 0.01). There was no significant difference among experimental groups in the number of spleen cells per gram of splenic tissue or in the histologic characteristics, indicating that C parvum stimulated relatively normal splenic growth. Survival following pneumococcal challenge was significantly increased for hemisplenectomized mice by C parvum treatment to a level that did not significantly differ from control mice. This study demonstrates that in mice the deficits related to resistance to infection and spleen size following hemisplenectomy are significantly improved by treatment with C parvum.