Increased susceptibility to pneumococci after ligation of the splenic artery in experimental hypersplenism.

22 male Sprague-Dawley rats were divided into two groups, of which group I received methylcellulose and group II saline intraperitoneally for 12 weeks. After ligation of the splenic artery of the animals in group I and sham operation of the rats in group II, the injections were continued for a further 9 weeks. At the operation, the group I animals all showed signs of hypersplenism with anemia, and leuko- and thrombocytopenia. The platelet counts normalized after the operation, a marked leukocytosis developed and the anemia was further aggravated. At the end of the study, the animals were challenged with 4 x 10(6) colony-forming units of pneumococci type 1, resulting in deaths of 11 of 12 animals in group I, in contrast to survival of all 10 rats in group II (p = 0.000017).