Vascular Remodeling and Immune Cell Infiltration in Splenic Artery Aneurysms.

Rupture of splenic artery aneurysms (SAAs) is associated with a high mortality rate. The aim of this study was to identify the features of SAAs. Tissue sections from SAAs were compared to nonaneurysmal splenic arteries using various stains. The presence of intraluminal thrombus (ILT), vascular smooth muscle cells (VSMCs), cluster of differentiation (CD)-68+ phagocytes, myeloperoxidase+ neutrophils, CD3+, and CD20+ adaptive immune cells were studied using immunofluorescence microscopy. Analysis of SAAs revealed the presence of atherosclerotic lesions, calcifications, and ILT. Splenic artery aneurysms were characterized by a profound vascular remodeling with a dramatic loss of VSMCs, elastin degradation, adventitial fibrosis associated with enhanced apoptosis, and increased matrix metalloproteinase 9 expression. We observed an infiltration of immune cells comprising macrophages, neutrophils, T, and B cells. The T and B cells were found in the adventitial layer of SAAs, but their organization into tertiary lymphoid organs was halted. We failed to detect germinal centers even in the most organized T/B cell follicles and these lymphoid clusters lacked lymphoid stromal cells. This detailed histopathological characterization of the vascular remodeling during SAA showed that lymphoid neogenesis was incomplete, suggesting that critical mediators of their development must be missing.

Patterns of splenic arterial enhancement on computed tomography scan are related to portal venous hypertension.

OBJECTIVES: We have previously shown that patterns of splenic arterial enhancement on computed tomography scan change following liver transplantation. We suggested that this is related to changes in portal venous pressure. The aim of this study was to see if similar patterns occur in patients with and without portal hypertension and in patients before and after portal systemic shunts (transjugular portosystemic shunts). METHODS: We evaluated contrast enhanced computed tomography scans in patients being evaluated for liver disease and compared those from patients with and without portal hypertension. In addition we evaluated patients who had computed tomography scans before and after transjugular portosystemic shunts shunts. Splenic arterial enhancement was evaluated using Hounsfield units (pixel counts). RESULTS: Twenty-four patients with clinically significant portal hypertension were compared to 91 without. Mean splenic pixel count was significantly lower in patients with clinically significant portal hypertension (88.2 ± 17.7 vs. 115.2 ± 21.0; m ± SD, P < 0.01). Computed tomography scans were available in 18 patients pre- and post-transjugular portosystemic shunts. Pixel counts were significantly higher in the post-transjugular portosystemic shunts scans (99.7 ± 20.9 vs. 88.9 ± 26.3; P < 0.05). CONCLUSION: This study supports the hypothesis that changes in portal venous pressure are related to changes in splenic arterial enhancement. We suggest that this reflects changes in the splenic micro-circulation. This mechanism may be part of the innate immune response and may also be important in the pathogenesis of hypersplenism.

Proximal Versus Distal Splenic Artery Embolisation for Blunt Splenic Trauma: What is the Impact on Splenic Immune Function?

PURPOSE: To compare the impact of proximal or distal splenic artery embolisation versus that of splenectomy on splenic immune function as measured by IgM memory B cell levels. MATERIALS AND METHODS: Patients with splenic trauma who were treated by splenic artery embolisation (SAE) were enrolled. After 6 months splenic volume was assessed by CT, and IgM memory B cells in peripheral blood were measured and compared to a local normal reference population and to a post-splenectomy population. RESULTS: Of the 71 patients who underwent embolisation, 38 underwent proximal embolisation, 11 underwent distal embolisation, 22 patients were excluded, 1 had both proximal and distal embolisation, 5 did not survive and 16 did not return for evaluation. There was a significant difference between splenectomy and proximal or distal embolisation and a trend towards greater preservation of IgM memory B cell number in those with distal embolisation-a difference that could not be attributed to differences in age, grade of injury or residual splenic volume. CONCLUSION: IgM memory B cell levels are significantly higher in those treated with SAE compared to splenectomy. Our data provide evidence that splenic embolisation should reduce immunological complications of spleen trauma and suggest that distal embolisation may maintain better function.

Preserved function after angioembolisation of splenic injury in children and adolescents: a case control study.

BACKGROUND: Non-operative management for blunt splenic injuries was introduced to reduce the risk of overwhelming post splenectomy infection in children. To increase splenic preservation rates, splenic artery embolization (SAE) was added to our institutional treatment protocol in 2002. In the presence of clinical signs of ongoing bleeding, SAE was considered also in children. To our knowledge, the long term splenic function after SAE performed in the paediatric population has not been evaluated and constitutes the aim of the present study. METHODS: A total of 11 SAE patients less than 17 years of age at the time of injury were included with 11 healthy volunteers serving as matched controls. Clinical examination, medical history, general blood counts, immunoglobulin quantifications and flowcytometric analysis of lymphocyte phenotypes were performed. Peripheral blood smears were examined for Howell-Jolly bodies (H-J bodies) and abdominal ultrasound was performed in order to assess the size and perfusion of the spleen. RESULTS: On average 4.6 years after SAE (range 1-8 years), no significant differences could be detected between the SAE patients and their controls. Total and Pneumococcus serospecific immunoglobulins and H-J bodies did not differ between the study groups, nor did general blood counts and lymphocyte numbers, including memory B cell proportions. The ultrasound examinations revealed normal sized and well perfused spleens in the SAE patients when compared to their controls. CONCLUSION: This case control study indicates preserved splenic function after SAE for splenic injury in children. Mandatory immunization to prevent severe infections does not seem warranted.

Preserved splenic function after angioembolisation of high grade injury.

BACKGROUND: After introducing splenic artery embolisation (SAE) in the institutional treatment protocol for splenic injury, we wanted to evaluate the effects of SAE on splenic function and assess the need for immunisation in SAE treated patients. METHODS: 15 SAE patients and 14 splenectomised (SPL) patients were included and 29 healthy blood donors volunteered as controls. Clinical examination, medical history, general blood counts, immunoglobulin quantifications and flowcytometric analysis of lymphocyte phenotypes were performed. Peripheral blood smears from all patients and controls were examined for Howell-Jolly (H-J) bodies. Abdominal doppler, gray scale and contrast enhanced ultrasound (CEUS) were performed on all the SAE patients. RESULTS: Leukocyte and platelet counts were elevated in both SAE and SPL individuals compared to controls. The proportion of memory B-lymphocytes did not differ significantly from controls in either group. In the SAE group total IgA, IgM and IgG levels as well as pneumococcal serotype specific IgG and IgM antibody levels did not differ from the control group. In the SPL group total IgA and IgG Pneumovax(®) (PPV23) antibody levels were significantly increased, and 5 of 12 pneumococcal serotype specific IgGs and IgMs were significantly elevated. H-J bodies were only detected in the SPL group. CEUS confirmed normal sized and well perfused spleens in all SAE patients. CONCLUSION: In our study non-operative management (NOM) of high grade splenic injuries including SAE, was followed by an increase in total leukocyte and platelet counts. Normal levels of immunoglobulins and memory B cells, absence of H-J bodies and preserved splenic size and intraparenchymal blood flow suggest that SAE has only minor impact on splenic function and that immunisation probably is unnecessary.

Phenotypic identification and development of distinct microvascular compartments in the postnatal mouse spleen.

In this paper we report the development of the sinus network of mouse spleen during the first postnatal month as studied with a set of new rat monoclonal antibodies (mAbs) against mouse splenic endothelial cell subpopulations. One of the new mAbs (IBL-7/1) also stained B-cell lineage cells in the spleen shortly after the birth as confirmed by three-color flow cytometry. This B-cell staining in the primordial follicles vanished by the fourth postnatal week, so that the expression of IBL-7/1 antigen was restricted to the marginal sinus endothelium and some red pulp sinuses and a minor B-cell subset in the spleen, presumably distinct from the follicular B-cell compartment. The other mAb (IBL-9/2) selectively labeled the sinusoids of the deeper part of the red pulp, without any reactivity against hemopoietic cells. The IBL-9/2-reactive cells in newborns appeared as isolated elements throughout spleen, and during the segregation of white and red pulps they formed an extensive network in the red pulp outside the marginal zone. Double-labeling immunofluorescence revealed that most of these sinusoids also stained weakly with IBL-7/1 mAb, whereas the strongly IBL-7/1-positive vessels of this region were IBL-9/2 negative. Neither of these mAbs reacted with the central artery. The comparative phenotypic analysis of the various vascular segments indicates that the splenic sinusoids of the marginal zone and red pulp, respectively, are lined with a heterogeneous array of endothelium. For the precise identification, isolation, and characterization of the possible homing function of these endothelium subsets these region-specific mAbs may be of potential value.

Electron microscopic localization of factor-VIII-related antigen in adult human blood vessels.

We have localized factor-VIII-related antigen, using immunofluorescence and electron microscopy, in adult human blood vessels. In addition to its presence in endothelial cells, the antigen was localized within subendothelium and the layers of elastic lamina closest to the lumen. Also, we provide the first morphological evidence that factor-VIII-related antigen is associated with collagen fibrils within the vessel wall. These studies suggest that this subendothelial factor-VIII-related antigen may play a role in the adhesion of platelets to subendothelial components following endothelial injury.

Quantitation of B and T lymphocytes in guinea pigs with evidence for a release of both cell types from the spleen into the blood.

B and T lymphocytes were quantitated in lymphoid organs and in blood of young normal guinea pigs by the use of EAC rosettes and rabbit erythrocyte (RE) rosettes as markers. Special attention was focused on the release of B and T cells from the spleen, estimated from the difference between the content of B and T cells in splenic efferent and afferent blood. The following frequencies of resette-forming cells (RFC) were found. Thymus: 0.3% EAC- and 88% RE-RFC; spleen: 44% EAC- and 46% RE-RFC; lymph nodes: 13% EAC- and 39% RE-RFC; arterial blood: 13% EAC- and 42% RE-RFC, and bone marrow: 2% EAC- and 7% RE-RFC. A fairly large number of cells in the lymph nodes and blood could not be identified by any of the two markers. Some possible explanations for this are discussed. The content of both EAC- and RE-RFC in splenic efferent blood significantly exceeded that in the afferent blood, indicating a release of both B and T cells from the spleen into the blood. The possibility of a release of a third type of mononuclear cell cannot be excluded from the present results.

Influence of adrenaline on the dissemination of antibody-producing cells from the spleen.

Plaque-forming cells (PFC) and rosette-forming cells (RFC) were quantificated in splenic venous and splenic arterial blood and in spleen suspensions of guinea-pigs during a secondary immune response to sheep red blood cells (SRBC). The splenic veno-arterial differences in content of PFC and RFC were determined, indicating whether there had been a release of such cells from the spleen into the blood. The effect of an intracardial injection of adrenaline on the release of immune lymphocytes was investigated. In immunized control animals a splenic release of antigen-binding and antibody-forming cells was found, the release being restricted to the peak of the immune response in the spleen. However, after exogenous adrenaline a considerably increased release of both antigen-binding and antibody-forming cells occurred during a longer period of the immune response. Thus, adrenaline caused an enormous release of PFC from the spleen into the blood on day 4 of the secondary immune response, resulting in a diminished number of PFC remaining in the spleen after the treatment. A physiological significance of an adrenaline-induced dissemination of immune lymphocytes in the body during an immune response to a severe infectious disease is suggested.

A comparative immunohistochemical study of splenic arterial hyalinosis in health and disease.

Hyaline deposits in arterioles and arteries of spleen were studied immunohistochemically. Hyaline lesions in arteriosclerotic heart disease were characterized by significant deposits of IgG, IgM, beta1C-beta 1A-globulins and beta-lipoproteins. These corresponded to histochemically stained deposits of acid mucopolysaccharides and microscopic areas of musculoelastic tissue damage in the hyaline masses. While, in young adults and a few other cases of other diseases, an occasional granular to linear deposit of IgG, IgM, beta1C-beta 1A-globulin and beta-lipoprotein was noted, no localization of IgA, rabbit antihuman fibrin and rabbit antihuman fibrinogen was seen. A variety of other histochemical staining reactions were found to be negative. These findings suggest that: a) hyaline deposits in splenic arterioles and arteries occur with greater severity in patients with hypertensive and arteriosclerotic heart disease; b) a possible abnormality related to filtration defects in arteries and arterioles, resulting in the trapping of plasma proteins, appears likely; c) increased localization of acid mucopolysaccharides and destruction of musculoelastic tissue is not an uncommon feature in hyaline masses; d) fibrin is not a component of these deposits and e) further study of other organs is necesary to observe the composition of hyaline in arterioles and arteries.