Humoral immunity in experimental hyposplenism.

The immune response to an intravenous bolus of sheep erythrocytes, a large particulate antigen, was examined in weanling Sprague-Dawley rats after varying reduction in spleen size by splenic artery ligation (SAL) or partial amputation (pSx), and the results were compared with splenectomized (Sx) and sham-operated controls. Whereas SAL and pSx rats both produced higher 5 day (primary response) hemolysin antibody titers (P less than 0.001) than Sx rats, levels were lower (P less than 0.05) than in sham-operated rats with larger spleens (P less than 0.001). A similar heterophile pattern was seen in SAL rats at 22 days (secondary response). Within each group there was a positive correlation between splenic weight and serum hemolysin titer (r greater than 0.81) (P less than 0.001). Whereas spleen weight of sham-operated rats increased only 58%, splenic remnants in pSx rats enlarged 139% to 412%, with the greatest percentage of growth in the smallest remnants (25 mg) and the least in the largest remnants (200 mg). These data demonstrate a measurable immunologic advantage of splenic remnants (hyposplenism) over asplenism. This difference, although suboptimal as compared with that of a whole spleen (eusplenism), nonetheless may bolster body defenses to certain forms of bacterial sepsis.