Increased Susceptibility of Splenectomized Rats to Infection with Diplococcus pneumoniae

• Published in: The Journal of infectious diseases 1972-11, Vol.126 (5), p.507-513
• Main Authors: Leung, Lai-Sung E., Szal, Gregory J., Drachman, Robert H.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Bacteria; Bacterial Vaccines - administration & dosage; Blood; Children; Disease Models, Animal; Disease Susceptibility; Immunization; Infections; Injections, Intravenous; Lethal Dose 50; Male; Methods; Mortality; Original Articles; Pneumococcal Infections - immunology; Pneumococcal Infections - mortality; Rats; Sepsis; Spleen; Spleen - immunology; Splenectomy; Streptococcus pneumoniae; Streptococcus pneumoniae - isolation & purification; Time Factors
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/126.5.507

An experimental model in the rat has been studied to determine the relationship of the spleen and immunization to challenge with Diplococcus pneumoniae virulent for the rat. An ld50 dose (105 bacteria) for normal rats of D. pneumoniae type 25, administered intravenously, caused 100% mortality in splenectomized rats. After inoculation, about 10 times as many D. pneumoniae were cultured from the blood of these rats as from normal controls. Immunization with homologous vaccine protected normal rats from challenge with the ld50. When splenectomy preceded immunization, all animals died after challenge. Mortality after injection of viable pneumococci decreased from about 80% to zero when the interval between immunization and subsequent splenectomy was lengthened from two to eight days. Immunization of normal rats caused a prompt and sustained clearance of bacteria from the bloodstream. It is hypothesized that, in the rat, the spleen is crucial for early clearance and for the initial immunologic response to bloodborne pneumococci, but becomes less important as the antibody response progresses.