Compensatory spleen growth and protective function in rats

Abstract

1. To quantify compensatory spleen growth after reduction in splenic mass and to determine the effect of age and vascular supply on remnant growth, we examined adult and weanling rats for remnant regeneration and adult rats for host protection against bloodstream pneumococcal challenge at intervals up to 180 days after partial resection or autograft implantation. 2. In adults, subtotally resected spleens with remnant blood flow and segmental anatomy otherwise intact (eutopic remnants) displayed prompt but relatively limited gains in remnant weight and nucleated cell number, and growth after 60 days was minimal; survival after pneumococcal challenge was directly related to initial remnant weight and unrelated to length of postoperative interval. Splenic autografts (ectopic remnants), by comparison, underwent necrosis early after devascularization, recovered initial remnant weight slowly, fell far short of restoring original cellularity, and even 6 months after implantation barely attained initial size; moreover, host protection against pneumococcaemia was no different in rats with autografts than in those with no residual spleen. Remnants in situ (both partial resection and whole spleens) grew more vigorously in weanling than adult rats. 3. The results suggest that splenic regeneration after either partial resection or implantation is much more limited than previously suggested, at least in disease-free rats, and is regulated by size and integrity of the initial remnant spleen, adequacy of vascular inflow, and age of the host. Whereas eutopic remnants provide protection against blood-borne pneumococcal challenge in proportion to initial residual size, ectopic remnants even with prolonged maturation fail to display immunoprotective function.

Non-Operative Management of Traumatized Spleen in Children: The Role of Open Abdominal Tap

“…Splenosis was once thought to protect splenectomised trauma patients from subsequent OPSI (15). This proved untrue, as adequate splenic function occurs only in the presence of at least 30°/o of original splenic mass witha normal or near normal blood supply (2,8,20).…”

“…In order to prevent unnecessary surgery in this group of patients, we recommend the use of the open abdominal tap. This technique has been shown to be rcliable and relatively safe (20). Since blood in the peritoneal cavity in this setting is an expected finding, a peritoneal tap consisting of elevated diastase levels or bacterja seen on gram stain of spun collected fluid indicates gastrointestinal o r pancreatic trauma.…”

Can partial splenectomy preserve humoral immunity in pediatric patients? Risks and benefits of partial splenectomy

“…(17,18) Van Wyck et al, have reported that preservation of a splenic remnant, approximately one-third the size of the normal spleen, seems critical to maintaining this protective effect in the rat. (19)(20)(21) Several authors have confirmed the effectiveness of partial splenectomy in the treatment of children with mild to moderate HS, reserving total splenectomy for severe disease. (14) Partial splenectomy is a viable option for selected patients with HS leading to improvement in hematologic and clinical abnormalities.…”

IgG-mediated phagocytosis in regenerated splenic tissue

“…The regeneration of splenie tissue after autotransplantation or splenic artery ligation in patients and in animal models is well described, but the capacity of such tissue to proteet against OPSI is controversial, some authors reporting benefit, others no improvement [8,9,[12][13][14][15][16][17], The spleen has two major functions in resistance to infection, the synthesis of specific opsonins or antibodies, and the clearance of poorly opsonized baeteria from the circulation. We have shown that antibody synthesis in humans and rats with regenerated splenic tissue is impaired [18,19], although significant and perhaps protective serum concentrations can be achieved by immunization.…”