Splenic phagocytic function after partial splenectomy and splenic autotransplantation

Reduction of rainbow trout spleen size by splenectomy does not alter resistance against bacterial cold water disease

In lower vertebrates, the contribution of the spleen to anti-bacterial immunity is poorly understood. We have previously reported a phenotypic and genetic correlation between resistance to Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD) and spleen somatic index (spleen weight normalized to body weight, SI). Fish families with larger pre-challenge SI values were found to have greater BCWD survival (resistance) following intraperitoneal injection of a lethal dose of F. psychrophilum. Since the mammalian spleen is known to be crucial for capture and destruction of encapsulated bacteria, we tested the hypothesis that reduction of spleen size, by surgical splenectomy, should reduce the survival advantage of the larger-spleen, disease-resistant fish. Experiments were performed using two separate lines of fish that had previously been selected either based on BCWD survival (resistant and susceptible), or selected based on spleen size (high and low SI). Following 65 to 81 days post-surgical recovery, fish were challenged with F. psychrophilum and mortality monitored for a minimum of 21 days. No significant difference in the relative survival was detected between splenectomized or sham-operated groups, while SI of splenectomized fish was reduced to an average of 8-12% of control animals. A positive correlation was observed between the SI, measured at the time of splenectomy, and time-to-death post-challenge. In summary, these experiments argue that larger spleen size alone is not sufficient for greater BCWD resistance, but rather it is an indirect indicator of immunological status.

Assessment of immune cells and function of the residual spleen after subtotal splenectomy due to splenomegaly in cirrhotic patients

Background

The spleen is thought to be central in regulating the immune system, a metabolic asset involved in endocrine function. Overwhelming postsplenectomy infection leads to a mortality rate of up to 50%. However, there is still controversy on performing subtotal splenectomy as treatment of splenomegaly due to portal hypertension in cirrhotic patients. In the present study, immunocytes and the indexes of splenic size, hemodynamics, hematology and immunology in the residual spleen were analyzed to support subtotal splenectomy due to splenomegaly.

Results

In residual spleen, T lymphocytes mainly were focal aggregation in the periarterial lymphatic sheath. While B lymphocytes densely distributed in splenic corpuscle. In red pulp, macrophages were equally distributed in the xsplenic cord and adhered to the wall of splenic sinus with high density. The number of unit area T and B lymphocytes of splenic corpuscle and marginal zone as well as macrophages of red pulp were obviously increased in the residual spleen, while the number of macrophages didn’t be changed among the three groups in white pulp. While there were some beneficial changes (i.e., Counts of platelet and leucocyte as well as serum proportion of CD3+ T cells, CD4+ T cells, CD8+ T cells were increased markedly; serum levels of M-CSF and GM-CSF were decreased significantly; The proportion of granulocyte, erythrocyte, megakaryocyte in bone marrow were changed obviously; But serum IgA, IgM, IgG, Tuftsin level, there was no significant difference; splenic artery flow volume, portal venous diameter and portal venous flow volume, a significant difference was observed in residual spleen) in the clinical indices.

Conclusion

After subtotal splenectomy with splenomegaly due to portal hypertension in cirrhotic patients, the number of unit area T and B lymphocytes, and MØ in red pulp of residual spleen increased significantly. However, whether increase of T, B lymphocytes and MØs in residual splenic tissue can enhance the immune function of the spleen, still need further research to confirm.

Critical mass of splenic autotransplant needed for the development of phagocytic activity in rats

When total splenectomy is inevitable, heterotopic splenic autotransplantation seems to be the only alternative to maintain the functions of the spleen. The present study was carried out to analyse the critical mass of splenic autotransplant (SAT) for the development of phagocytic activity in rats. Wistar rats were submitted to total splenectomy (TS) alone or in combination with slices of SAT ranging from an average rate of 21·9% (one slice) to 100% (five slices) of the total splenic mass implanted into the greater omentum. Sixteen weeks after the beginning of the experiment, the animals were inoculated intravenously with a suspension of Escherichia coli labelled with Tc-99m. After 20 min, the rats were killed and the liver, lung and spleen or SAT, as well as blood samples were removed to determine the percentage of labelled bacteria uptake in these tissues. As the percentage of the total splenic mass contained in the SAT increased, the bacteria remaining in the blood decreased. From the implant of 26% up to the implant of the total splenic mass (100%) there was no difference in the bacteria remaining in the blood between the healthy animals of the control group and those submitted to TS combined with SAT. This finding shows that the critical mass needed for the development of phagocytic activity of macrophages in splenic autotransplants in adult rats is 26% of the total splenic mass.

A new technique for partial splenectomy with radiofrequency technology

The advantage of partial splenectomy is the preservation of its immunologic function. In this series, 8 patients underwent a spleen preservation procedure with radiofrequency. Four of the partial splenectomy procedures were performed in elective situations, whereas the other 4 cases were performed to control traumatic bleeding in emergency situations. A harrow-like radiofrequency probe with 6 needles was applied to the spleen, and the division of the splenic parenchyma was completed using a surgical scalpel through the midline of the ablated tissue. This safe, fast, and simple technique allows for preservation of splenic function with minimum blood loss.

Involvement of remnant spleen volume on the progression of steatohepatitis in diet-induced obese rats after a splenectomy

AIM

  This study investigated the correlation between remnant spleen volume after splenectomy (SPX) and the degree of hepatic steatosis and/or inflammation.

METHODS

  Male Sprague-Dawley rats were fed HF food and divided into three groups: sham-operation (Sham) group, a hemisplenectomy (H-SPX) group, and a total-splenectomy (T-SPX) group. Serum was collected and livers removed 12 weeks after surgery. We measured serum lipid markers and evaluated liver changes by comparing the three groups. Additionally, we examined liver changes 24 weeks after SPX.

RESULTS

  Serum triglyceride and free fatty acid levels after SPX were higher than those of sham controls, and a significant difference was found between T-SPX and the other groups (P < 0.05 for each). Increased intrahepatic fat accumulation was shown in SPX rats along with lower residual spleen volume; this fat accumulation after SPX was accelerated in rats at 24 weeks. Additionally, liver inflammatory changes, including an increase in the Kupffer cell population and pro-inflammatory cytokine production, as well as a high level of oxidative stress, were observed in the liver sections from SPX rats, which correlated significantly with less volume of the residual spleen. Also, an increase in pro-inflammatory cytokine content and a decrease in anti-inflammatory cytokine content were shown in the residual spleen from H-SPX rats, as compared to those of sham controls (P < 0.05 for each).

CONCLUSION

  These results indicate the importance of preserving splenic tissue. This residual spleen may play an important role in preventing the progression from diet-induced hepatic steatosis to steatohepatitis.

Hereditary spherocytosis and partial splenectomy in children: review of surgical technique and the role of imaging

The risks associated with total splenectomy, including overwhelming postsplenectomy infection, have led to an interest in the use of partial splenectomy as an alternative surgical option for children with congenital hemolytic anemias and hypersplenism. Partial splenectomy, a procedure designed to remove enough spleen to improve anemia and avoid complications of splenic sequestration while preserving splenic function, has shown promise in children. Radiologic imaging is essential for the preoperative evaluation and postoperative care for children undergoing partial splenectomy and offers a broad range of critical clinical information essential for care of these complex children. It is imperative for radiologists involved in the care of these children to be familiar with the surgical technique and imaging options for these procedures. This article reviews the surgical technique as well as the current status of various diagnostic imaging options used for children undergoing partial splenectomy, highlighting technical aspects and specific clinical information obtained by each modality.

Partial splenectomy in the management of nonparasitic splenic cysts

BACKGROUND

Recognition of the importance of the spleen in immunological function and the potential threat of severe postsplenectomy complications have led to the development of parenchyma-preserving surgical procedures. The aim of the present study was to assess the impact of open splenic partial resection on the management of splenic cysts.

PATIENTS AND METHODS

From April 2003 to June 2007, 11 patients with splenic cysts were evaluated. All patients fulfilled the criteria for surgical resection. Ten of the patients (6 women and 4 men) 15-42 years of age (mean: 26.4 years) were subjected to open partial splenectomy. In one patient, a centrally located splenic cyst was considered unsuitable for partial splenectomy, and the patient therefore underwent total spleen excision. Patients with splenic cysts constituted 3.8% of all 290 patients subjected to splenectomy during the study period. Spleen parenchyma was cut with the aid of a LigaSure instrument. Bleeding from the transected splenic parenchyma was secured with argon plasma coagulation and absorbable tape sutures or oxidized cellulose.

RESULTS

Nine of the ten patients underwent successful partial splenectomy. In one patient, insufficient arterial supply to the preserved splenic remnant after excision of the upper cyst-containing splenic pole led to total splenectomy. The mean operative time was 98 min (range: 85-160 min), and mean blood loss was 106 ml (55-200 ml). The mean cyst diameter was 9.1 cm (range: 7-17 cm) and weight was 738 g (range: 230-2,420 g). The postoperative course was uneventful in all cases. Pathological examination showed an epithelial cyst in 8 patients and a pseudocyst in 2. After a mean follow-up of 26.4 months, the size of the splenic remnant constituted, on average, 71% of preoperative spleen size. Moreover, normal splenic vein flow was observed. Platelet counts remained within the normal range, and no cyst recurrence was observed. There were no infections documented during the follow-up period.

CONCLUSIONS

Open partial splenectomy is a safe and effective method in the management of nonparasitic splenic cysts. It ensures complete cyst removal, lack of cyst recurrence, and preservation of the spleen functions.

Partial splenectomy for hereditary spherocytosis

The significant risks associated with total splenectomy have led to interest in the use of partial splenectomy as an alternative surgical therapy for children who have congenital hemolytic anemia. Partial splenectomy is designed to remove enough spleen to gain desired hematologic outcomes while preserving splenic immune function. Although preliminary data demonstrate successful laboratory and clinical outcomes after partial splenectomy in various congenital hemolytic anemias, conclusive data comparing the efficacy of partial splenectomy to total splenectomy are not reported. Based on preliminary data, a definitive clinical trial of partial splenectomy in children who have severe congenital hemolytic anemia may be warranted.

A case of splenic abscess after radiofrequency ablation

Radiofrequency ablation (RFA) is an innovative technique used primarily for the palliative treatment of unresectable liver tumors. Its therapeutic indications however, have been expanded and now include various other organs and diseases. There is a paucity of data regarding technical details and complications of the use of RFA in the spleen. We report a case of partial splenectomy using radiofrequency ablation for splenic hydatid disease, complicated by an abscess formation.

Morfologia e função fagocitária de implante esplênico autógeno regenerado em ratos

Objetivo: O objetivo deste trabalho é analisar a regeneração morfológica de tecido esplênico auto-implantado em ratos Wistar, verificando a função fagocitária bacteriana de seus macrófagos. Métodos: Utilizou-se um modelo experimental com ratos jovens e adultos, de ambos os sexos, submetidos a esplenectomia total combinada com auto-implante de fatias de toda a massa esplênica no omento maior. Dezesseis semanas após, os animais foram inoculados por via intravenosa com suspensão de Escherichia coli AB1157 e, após 20 minutos, foram mortos por dose letal de halotano, sendo submetidos a laparotomia para retirada dos auto-implantes esplênicos. A análise estatística foi realizada com o teste t de Student, com ênfase na comparação da massa de auto-implante esplênico regenerada entre animais jovens e adultos de ambos os sexos. Resultados: Ocorreu regeneração do auto-implante esplênico em todos os animais. Machos jovens e fêmeas adultas apresentaram maior percentual de regeneração. Observou-se aspecto morfológico microscópico semelhante em todos os animais. O tecido esplênico regenerado mostrou as polpas vermelha e branca, com desarranjo arquitetural moderado, bem como folículos linfóides. Os vasos sangüíneos mostravam paredes preservadas, sem sinais de vasculite ou trombose. Foram encontrados macrófagos contendo grumos de bactérias, bem como macrófagos contendo pigmento de hemossiderina intracitoplasmáticos. Conclusão: O auto-implante esplênico, no omento maior, em ratos, adquire a arquitetura macro e microscópica de um baço normal, de dimensão menor e preserva a função fagocitária bacteriana.

The relationship between partial splenectomy and peripheral leukocyte count

BACKGROUND

Partial splenectomy is accepted as a treatment modality for hypersplenism permitting preservation of the spleen functions. Since a prominent leukocytosis is a marked event after total splenectomy, it was the aim of the present study to compare the peripheral white blood cell counts (PWBC) and immune response in mice following partial and total splenectomy.

MATERIALS AND METHODS

Four groups of animals were included in the study: mice in which 70% of the spleen was removed, animals that underwent total splenectomy, mice with sham operation, and a group of mice that served as controls. The proliferative response of peripheral blood mononuclear cells, peritoneal cells, and splenocytes was examined using concavalin (Con) A.

RESULTS

In distinction from marked leukocytosis observed in mice after total splenectomy, in partially splenectomized mice the PWBC counts did not show any significant increase during a follow-up period of up to 2 months after surgery. The mitogen response of the mononuclear cells to Con A in partially splenectomized mice was similar to that of controls, while in animals after total splenectomy, it was increased in cells from the peripheral blood and decreased in those from the peritoneum.

CONCLUSIONS

The results indicate that removal of as much as about 70% of the spleen in mice is sufficient to maintain a normal PWBC count, suggesting a regulatory role of the spleen remnant on the PWBC production. The normal mitogen response of the cells to Con A indicates that the spleen rudiment preserves at least a part of the immune activity of the intact spleen.

Distribuição de Escherichia coli nos órgãos do sistema mononuclear fagocitário após esplenectomia total isolada ou combinada com auto-implante esplênico em rato

OBJETIVO: O auto-implante esplênico parece constituir a única alternativa para preservação de tecido esplênico, após esplenectomia total. O objetivo deste trabalho foi analisar a depuração de Escherichia coli pelos órgãos do sistema mononuclear fagocitário (SMF) após esplenectomia total e auto-implante esplênico. MÉTODO: Utilizou-se um modelo experimental com ratos Wistar jovens e adultos, de ambos os sexos, submetidos a esplenectomia total e auto-implante esplênico. O método de avaliação foi a inoculação intravenosa de suspensão de Escherichia coli marcada com tecnécio - 99m. Analisou-se a captação desta bactéria pelos órgãos do SMF e o remanescente bacteriano na corrente sangüínea. RESULTADOS: Dentro de cada grupo, não foi encontrado diferença entre animais jovens e adultos no que se refere à captação de bactérias pelos órgãos do SMF. Na comparação entre os grupos verificou-se que o percentual médio de captação pelo baço e pelo fígado de animais do Grupo-Controle foi maior que o dos auto-implantes. Embora a captação de bactérias pelo baço de animais do Grupo-Controle tenha sido maior que o dos auto-implantes esplênicos, o remanescente bacteriano no sangue não foi diferente. Animais submetidos a esplenectomia total isolada apresentam maior remanescente de bactérias na corrente sangüínea que animais do Grupo-Controle ou do grupo submetido a esplenectomia total combinada com auto-implante esplênico. CONCLUSÃO: Nossos resultados indicam que o auto-implante esplênico é eficaz na depuração de bactérias, em rato, mediante a fagocitose por seus macrófagos, e não interfere na função de remoção bacteriana do fígado e do pulmão.

Bacterial phagocytosis by macrophage of autogenous splenic implant

Autogenous splenic implant seems to be the only alternative for preservation of splenic tissue after total splenectomy. This work was carried out to analyze the morphologic regeneration of autotransplanted splenic tissue in Wistar rats and to determine the bacterial phagocytic function of their macrophages. We utilized an experimental model with thirty-two rats, of both sexes, submitted to total splenectomy combined with autotransplantation in greater omentum of slices of the whole spleen mass. The animals were divided into two groups: I - young rats weighing 100 to 150 g; and II - adult rats weighing 250 to 300 g. Sixteen weeks later animals were intravenously inoculated with a suspension of Escherichia coli AB1157. Twenty minutes after inoculation, the animals were sacrificed and the splenic autotransplants were removed for morphological study. There was regeneration of autotransplanted splenic tissue in all animals. A similar morphological aspect among all animals was observed, with splenic tissue showing red and white pulps, lymphoid follicles, and marginal zone, with a moderate architectural disarrangement. Macrophages containing gram-negative bacterial aggregates as well as macrophages with hemosiderin pigments within the cytoplasm were observed. Blood vessels showed preserved walls, with no signs of vasculitis or thrombosis. The present results suggest that autogenous splenic implants in the greater omentum of the rat acquire the macro- and microscopic architecture of a normal spleen, with reduced dimensions, and preserve bacterial phagocyte function.

How we do a bloodless partial splenectomy

Partial splenectomy and Tru-cut biopsy are not routinely practiced because of the lack of vascular control to arrest bleeding. Using radiofrequency energy to coagulate the resection margin and biopsy tract, a 74-year-old woman with a tumor in the lower pole of the spleen underwent partial splenectomy and Tru-Cut biopsy of the spleen. Hemostasis was excellent. Blood loss was minimal and the patient was discharged with a functioning spleen. This new technique may allow safe and bloodless partial splenic resection and Tru-cut biopsy of the spleen, which might reduce the number of splenectomies performed and the consequent difficulties for the patient that can arise.

Clinical and hematologic benefits of partial splenectomy for congenital hemolytic anemias in children

OBJECTIVE

To assess the role of partial splenectomy for symptomatic children with various congenital hemolytic anemias.

SUMMARY BACKGROUND DATA

The use of total splenectomy for symptomatic children with congenital hemolytic anemias is restricted by concern of postsplenectomy sepsis. A partial splenectomy is an alternative procedure, although its utility remains incompletely defined.

METHODS

This longitudinal cohort study followed 25 symptomatic children with various congenital anemias who underwent partial splenectomy. Sixteen children had hereditary spherocytosis (HS), and nine children had other erythrocyte disorders. Outcome measures were clinical and laboratory hemolysis, splenic phagocytic and immune function, and splenic regrowth as measured by ultrasonography. Discrete parameters were compared using the Student test.

RESULTS

Partial splenectomy was successful in all 25 children, with minimal morbidity. Follow-up ranged from 7 months to 6 years (mean 2.3 +/- 1.5 years). Following surgery, children with HS had increased hemoglobin values, decreased reticulocyte and bilirubin levels, and preserved splenic function. Most children without HS had decreased symptoms of hypersplenism and splenic sequestration. Over time, variable rates of splenic regrowth were noted, although regrowth did not necessarily correlate with recurrent hemolysis.

CONCLUSIONS

In children with hereditary spherocytosis, a partial splenectomy appears to control hemolysis while retaining splenic function. In children with other congenital hemolytic anemias, a partial splenectomy appears to control symptoms of hypersplenism and splenic sequestration.

Bacterial clearance after total splenectomy and splenic autotransplantation in rats

Wistar rats submitted to isolated total splenectomy or total splenectomy combined with splenic autotransplantation were inoculated with 99mtechnetium-labeled Escherichia coli. Measurement of isotope uptake in the organs of the mononuclear phagocytic system showed a greater bacterial bloodstream clearance in rats with splenic autotransplantation. Although uptake of bacteria in the spleen was higher in the control group, the number of bacteria remaining in the bloodstream did not differ between groups. These results indicate that splenic autotransplantation preserves the phagocytic function of the spleen.

Dental considerations in asplenic patients

The spleen plays an important role in the body's defense mechanism against microbial infections. However, trauma or diseases sometimes make removal of this important organ necessary, which predisposes patients to certain infections. This increased risk of infection and the underlying reason for the organ's removal both may affect the provision of dental care. This article reviews the structure and function of the spleen, conditions that may require its removal or cause its dysfunction, and provides considerations for dentists who care for asplenic patients.

IgG-mediated phagocytosis in regenerated splenic tissue

The risk of severe infections after splenectomy is well established. Operations such as auto-transplantation, splenic artery ligation or partial resection have been advocated for the retention or regeneration of splenic tissue following splenic trauma. The potential of such tissue to protect from infection is unclear. The ability of splenic tissue to phagocytose IgG opsonized syngeneic erythrocytes was measured in rats 6 months following splenectomy and splenic autotransplantation, splenic artery ligation, total or partial splenectomy, and compared with eusplenic controls. In eusplenic and partially splenectomized rats 71% of the label was cleared at 3 h, compared with approximately 50% in rats following total splenectomy, splenectomy and splenic autotransplantation or splenic artery ligation. The autotransplanted and the ligated splenic tissue cleared less than 10% compared with control spleen, but there was no difference between them when clearance was expressed as uptake per gram of tissue. Splenic autotransplants and ligated spleens were small and histologically abnormal, with an increase in the red pulp, significantly less white pulp and marginal zone, and the frequent absence of a central arteriole in the white pulp. The clearance of label was proportional to the amount of red pulp in the tissue, although the red pulp from the regenerated tissues was not as efficient at phagocytosis as control red pulp. The tissue which regenerated following autotransplantation or splenic artery ligation did not result in greater clearance of erythrocytes from the circulation than that which occurred in splenectomized rats.

Autologous splenic transplantation for splenic trauma

OBJECTIVE

The authors reviewed the experimental evidence, surgical technique, complications, and results of clinical trials evaluating the role of autologous splenic transplantation for splenic trauma.

SUMMARY BACKGROUND DATA

Splenorrhaphy and nonoperative management of splenic injuries have now become routine aspects in the management of splenic trauma. Unfortunately, not all splenic injuries are readily amenable to conventional spleen-conserving approaches. Heterotopic splenic autotransplantation has been advocated for patients with severe grade IV and V injuries that would otherwise mandate splenectomy. For this subset of patients, splenic salvage by autotransplantation would theoretically preserve the critical role the spleen plays in the host's defense against infection.

METHODS

The relevant literature relating to experimental or clinical aspects of splenic autotransplantation was identified and reviewed. Data are presented on the experimental evaluation of autogenous splenic transplantation, methods and complications of autotransplantation, choice of anatomic site and autograft size, and results of clinical trials in humans.

RESULTS

The most commonly used technique of autotransplantation in humans involves implanting tissue homogenates or sections of splenic parenchyma into pouches created in the gastrocolic omentum. Most authors have observed evidence of splenic function with normalization of postsplenectomy thrombocytosis, immunoglobulin M levels, and peripheral blood smears. Some degree of immune function of transplanted grafts has been demonstrated with in vivo assays, but the full extent of immunoprotection provided by human splenic autotransplants is currently unknown.

CONCLUSIONS

Multiple human and animal studies have established that splenic autotransplantation is a relatively safe and easily performed procedure that results in the return of some hematologic and immunologic parameters to baseline levels. Some aspects of reticuloendothelial function are also preserved. Whether this translates into a real reduction in the morbidity or mortality rates from overwhelming bacterial infection is unknown and requires further investigation.

Subtotal splenectomy in Gaucher's disease: towards a definition of critical splenic mass

Partial splenectomy is currently the favoured surgical approach for Gaucher's disease. Preservation of splenic tissue is indicated to prevent susceptibility to overwhelming postsplenectomy sepsis, to delay the massive deposition of glucocerebroside in the liver and bones, and to relieve symptoms of hypersplenism. Controversial issues and technical problems related to partial splenectomy for Gaucher's disease are discussed and a definition of critical splenic mass considered.

Regeneration of autotransplanted splenic tissue at different implantation sites

Inbred animals (Lewis rats) were used to investigate the regeneration of autologously implanted splenic tissue at intra-omental and subcutaneous sites. Quantitative immunohistology with monoclonal antibodies against lymphocytes and macrophages was performed to analyse the cell density of red pulp (RP), periarteriolar lymphoid sheath (PALS), marginal zone (MZ) and follicle, 7-180 days after transplantation. Antigenic, allogeneic and mitogenic stimulation and Northern blotting were also performed. Transplant groups differed from spleen only in the reduced size of PALS; however, quantitative analysis demonstrated subtle differences between spleen and transplants. The cell density of B-cells and ED-1+ macrophages was reduced in the RP, Tsupp/cyt-cells were decreased and B-cells increased in PALS, and B-cells and Thelper-cells reduced in the MZ. No differences could be detected between the transplant groups. Flow-cytometric analysis of cell suspensions from spleen and transplants revealed a reduction of T-cells (OX-19+), MHC-I and transferrin-receptor-bearing cells in both transplant groups, and a decrease in the number of Thelper-cells and ED-3+ macrophages in subcutaneous transplants. Both transplant groups were defective regarding the allogeneic and pokeweed mitogen response. Aberration of the lipopolysaccharide response was restricted to subcutaneous transplants, which additionally showed abnormal expression of interferon-gamma, interleukin-5 and interleukin-6 mRNA. Thus, subtle alterations of the newly developed microenvironment and/or lymphocyte-homing may influence the regeneration of splenic tissue; the implantation site may represent an important parameter in functional reorganisation.

Regeneration of the spleen and splenic autotransplantation

This paper reviews the subject of regeneration of the spleen and discusses the role of splenic autotransplantation following splenectomy for trauma.

Regeneration and phagocytic function of devascularized spleens

The phagocytic function of normal splenic tissue and of regenerated tissue following splenic artery ligation was investigated in rats using radiolabelled stannous fluoride colloid. Colloidal carbon was used to determine the histological location of phagocytosis within the spleen. Six months after ligation, the median weight of the devascularized spleens was 25% of that of spleens in control rats. Technetium stannous colloid clearance by devascularized spleens was reduced to 10% of normal and 25% when corrected for spleen weight. The colloidal carbon injected intravenously was observed primarily in the marginal zone in both normal and devascularized spleens. Histologically, devascularized spleens contained significantly less white pulp and marginal zone. The splenic tissue which regenerates following ligation does not have the phagocytic ability of normal splenic tissue. This may be due to the decreased regrowth of the lymphoid compartments of the spleen.

Electron microscopic study of subcutaneous and intraperitoneal splenules in the mouse

The development of splenules derived from slices of freshly removed autologous spleen implanted subcutaneously or intraperitoneally was followed by light and electron microscopy from day 2 to day 70. Within 48 hr after transplantation, a rough space filled with blood, unlined by endothelium, formed just under the surface of the splenic fragment. The tissue central to this vascular space was disrupted and necrotic. In the outer portion of the vascular space, fibroblasts appeared and created locules which developed into a highly vascular, hematopoietic red pulp. From the inner portion, blood percolated into the central necrotic tissue. At 1 week the splenule was divisible into concentric structures. The capsule was outermost. A shell of vascularized, highly hematopoietic red pulp lay within the capsule, having replaced the vascular space. Central to the red pulp lay a band of fibroblasts and macrophages. Next was a layer of fibroblasts in a matrix of degenerating cells, and, at the center, a necrotic core. As fibroblasts and macrophages moved centrad, the red pulp moved with them, expanding and replacing the necrotic tissue. The splenule differed in character from the original spleen. Splenular red pulp, especially near the surface, was unusually hematopoietic. The circumferential reticulum of white pulp was reduced or absent, and the boundary between red and white pulp was sometimes indistinct. Some white pulp was subcapsular, and the capsule and surrounding connective tissue were infiltrated by lymphocytes. The necrotic core of the splenule was typically surrounded by a zone containing large blood vessels, connective tissue, and adipocytes.

Reticuloendothelial clearance and splenic mononuclear cell populations after resection and autotransplantation

Although the preservation of splenic tissue may prevent overwhelming infection after splenectomy, the degree of protection conferred by small remnants has not been optimal. We investigated whether either splenic reticuloendothelial clearance of a blood flow-dependent colloid or macrophage and T-cell populations might be altered by resection or autotransplantation of the spleen. Our results have shown that bloodstream reticuloendothelial clearance of technetium 99m sulfur colloid is not impaired by splenectomy, partial resection of the spleen, or splenic autotransplantation. Such clearance is dependent on spleen weight and is not related to differences in either macrophage or helper or suppressor T-cell populations. This suggests that autotransplantation of the spleen is inferior to preservation of even a small hilar remnant and implies that repair or partial resection of the spleen will provide greater protection than autotransplantation.

Does the spleen regenerate after partial splenectomy in the dog?

Four dogs underwent two thirds partial splenectomy and the remaining spleens were followed up to 6 months by radioisotope studies and finally measured at the time of sacrifice. In this study we showed that the remaining spleens after partial splenectomy did not show any signs of regeneration.

Phagocytic activity of Kupffer cells in splenectomized rats

Carbonized polyethylene microspheres of 3.53 micron diameter were injected intravenously into splenectomized, laparotomized, and untreated rats. The number of Kupffer cells which phagocytosed microspheres and the number of microspheres phagocytosed by single Kupffer cells were counted. The number of Kupffer cells which phagocytosed microspheres was 1.51 times greater in splenectomized rats than in untreated rats, and 1.29 times greater in splenectomized rats than in laparotomized rats, both values being statistically significant. Although this same value was 1.18 times greater in laparotomized rats than in untreated rats, this was not statistically significant. The number of microspheres phagocytosed by single Kupffer cells also increased significantly in splenectomized rats. The intra-acinar distribution of the phagocytosing Kupffer cells showed the number in the periportal area to be 8-9 times greater than in the central area in all 3 groups. No significant difference in this intra-acinar distribution was observed between the groups. In addition, there was no difference in the phagocytic activity of Kupffer cells and the distribution of phagocytosing Kupffer cells between the hepatic lobes.

Heterotopic autologous splenic grafts in rat. Morphological studies

Splenic grafts autotransplanted at splenectomy into the omentum of 23 Porton strain rats were compared with spleens from 10 sham-operated controls. Six months after transplantation, the grafts weighed between 81 to 545 mg (median 166 mg) compared to control spleens which weighed 775 to 1,250 mg (median 995 g). Histoquantitation of the grafts revealed marked reduction of the splenic white pulp when compared to control spleens. Morphological examination showed not only a reduction of lymphocytes but also a striking architectural abnormality in all grafts. In 2 of the transplants, no lymphoid aggregates were observed; small subcapsular collections were present in 7, while in 8, isolated perivascular aggregates of lymphocytes with poorly formed marginal zones were observed. Only 6 transplanted spleens showed linkage of adjacent lymphoid aggregates but the number and size of these aggregates were clearly less than normal. These findings indicate that autotransplanted splenic tissue in rats does not regain histological normality. The implications of these observations for autotransplantation in splenectomized patients are discussed.

The influence of splenic weight and function on survival after experimental pneumococcal infection

Splenectomy impairs survival after pneumococcal challenge in rats, while preservation of sufficient splenic tissue can be protective. This study investigated the effects of methylcellulose on stimulation of splenic weight, splenic histology, reticuloendothelial (RE) activity, and survival after pneumococcal infection. Methylcellulose increased spleen weight four- to five-fold but did not improve RE function or survival after infection. These parameters correlated best with the weight of the remnant in animals that did not receive methylcellulose. The functional limitations of splenic autotransplants were not corrected by methylcellulose stimulation of splenic weight. Preservation of a splenic remnant with intact blood supply is preferable to autotransplantation of the spleen to conserve RE capability.

Response to immunization after partial and total splenectomy

Survival after infection from Streptococcus pneumoniae in both animals and man is influenced by the amount of splenic tissue. We investigated the effect of differences in splenic weight upon the antibody response to immunization and the effect of immunization upon survival after pneumococcal challenge. Young Sprague-Dawley rats had either sham operation, hemisplenectomy, splenectomy with splenic autotransplantation, or total splenectomy. Nine weeks later, rats were immunized with a heat- and formalin-killed type-specific pneumococcal vaccine. Antibody response measured by radioimmunoassay was similar in all operative groups and was significantly higher than in nonimmune rats (P less than 0.01). Splenic weight was less after hemisplenectomy or autotransplantation than in sham-operated animals (P less than 0.01). Immunization improved survival after live pneumococcal challenge in rats that had autotransplantation and total splenectomy (P less than 0.001). Our results demonstrate that splenic weight does not affect the antibody response to pneumococcal immunization in rats. Immunization improves survival after bacterial challenge in susceptible animals and minimizes the detrimental effect of reduction in splenic mass.