The spleen and splenectomy in immune (idiopathic) thrombocytopenic purpura

Splenomegaly and Response to Splenectomy in Immune Thrombocytopenia

Background: Immune thrombocytopenia (ITP) is an acquired autoimmune disorder affecting patients of all ages and backgrounds. While current standards favor medical therapy in the frontline setting, splenectomy remains an integral part of treatment in refractory cases. Ideal parameters for patient selection for surgery remain elusive. Methods: Data for 40 adult patients undergoing splenectomy for ITP at a large urban center between 1 January 2010 and 1 July 2021 were collected and analyzed. Results: Most patients underwent uneventful laparoscopic splenectomy (95%). Complete or partial response at the time of last follow-up occurred in most patients (92.5%), with 60.0% requiring no additional medical therapy following surgery. Thrombosis was the predominant adverse event and the leading cause of death for two patients. Age and presence of splenomegaly appear to be associated with response to splenectomy. Conclusions: Splenectomy remains an effective therapy for selected patients with ITP. Predictors of positive response to splenectomy, such as younger age and the presence of splenomegaly, may help inform clinicians during patient selection for therapy. With strict attention paid to postoperative thromboprophylaxis, the diminishing use of splenectomy may not be warranted.

Autologous platelet scintigraphy and clinical outcome of splenectomy in immune thrombocytopenia: A systematic review and meta-analysis

Autologous platelet sequestration pattern is associated with post-splenectomy platelet response in patients with immune thrombocytopenia (ITP). However, published results are contradictory, and have not been systematically reviewed. Our aim is to systematically review and meta-analyse the association between sequestration pattern and post-splenectomy platelet response. Articles were selected from MEDLINE when they a) included ITP patients, b) performed scintigraphy, and c) included post-splenectomy platelet response. The 23 included studies (published between 1969-2018) represented 2966 ITP-patients. Response to splenectomy occurred most frequently in patients with a splenic pattern (87.1 % in splenic versus 47.1 % in mixed and 25.5 % in hepatic patterns). A pooled analysis of 8 studies showed an odds ratio of 14.21 (95 % CI: 3.65-55.37) for platelet response in the splenic versus the hepatic group. Our findings indicate that a splenic sequestration pattern is associated with better response after splenectomy. Platelet sequestration patterns may be useful in the clinical decision-making regarding splenectomy.

Association of Immune Thrombocytopenia and T-Lymphoblastic Lymphoma in a Pediatric Patient

Immune thrombocytopenia (ITP) is characterized by isolated thrombocytopenia of unclear etiology. We present a unique case of an 8-year-old girl with chronic ITP who was subsequently diagnosed with T-lymphoblastic lymphoma at age 11. The clinical course was complicated by the occurrence of nonepileptiform events with bizarre behavior changes following the administration of nelarabine and intrathecal and high-dose systemic methotrexate. This case highlights an unusual co-occurrence of hematologic malignancy and chronic ITP in an otherwise healthy child. We speculate that underlying genetic or immunologic lesions may predispose a subset of pediatric ITP patients to the development of hematologic malignancies.

Red pulp macrophages in the human spleen are a distinct cell population with a unique expression of Fc-γ receptors

Tissue-resident macrophages in the spleen play a major role in the clearance of immunoglobulin G (IgG)-opsonized blood cells, as occurs in immune thrombocytopenia (ITP) and autoimmune hemolytic anemia (AIHA). Blood cells are phagocytosed via the Fc-γ receptors (FcγRs), but little is known about the FcγR expression on splenic red pulp macrophages in humans, with only a few previous studies that showed conflicting results. We developed a novel method to specifically isolate red pulp macrophages from 82 human spleens. Surface expression of various receptors and phagocytic capacity was analyzed by flow cytometry and immunofluorescence of tissue sections. Red pulp macrophages were distinct from splenic monocytes and blood monocyte-derived macrophages on various surface markers. Human red pulp macrophages predominantly expressed the low-affinity receptors FcγRIIa and FcγRIIIa. In contrast to blood monocyte-derived macrophages, red pulp macrophages did not express the inhibitory FcγRIIb. Red pulp macrophages expressed very low levels of the high-affinity receptor FcγRI. Messenger RNA transcript analysis confirmed this expression pattern. Unexpectedly and despite these differences in FcγR expression, phagocytosis of IgG-opsonized blood cells by red pulp macrophages was dependent on the same FcγRs as phagocytosis by blood monocyte-derived macrophages, especially in regarding the response to IV immunoglobulin. Concluding, we show the distinct nature of splenic red pulp macrophages in human subjects. Knowledge on the FcγR expression and usage of these cells is important for understanding and improving treatment strategies for autoimmune diseases such as ITP and AIHA.

Association of cytotoxic T-lymphocyte antigen 4 gene with immune thrombocytopenia in Chinese Han children

OBJECTIVES

To investigate the association of cytotoxic T lymphocyte-associated antigen 4 (CTLA4) with immune thrombocytopenia (ITP).

METHODS

A case-control association analysis of 277 Chinese Han children was performed. The tagging variants rs11571315 and rs3087243 in the CTLA4 gene were detected using polymerase chain reaction-restriction fragment length polymorphism method. The expression quantitative trait loci (eQTL) analysis and quantitative real-time polymerase chain reaction were performed to determine the relationship of CTLA4 with ITP.

RESULTS

Neither SNP was significantly different between case and control groups in either the genotypic or allelic distribution. The eQTL analysis results indicated that in the spleen, the rs3087243 was significant with the expression of CTLA4. The rs11571315 has similar results. Interestingly, the transcript level of CTLA4 was found to significantly decrease in patients with ITP.

DISCUSSION

The autoimmune and gene etiology is implicated in the pathogen of ITP. The CTLA4 is important for negative regulation of T-cell activation, and CTLA-4 gene has been identified as a risk factor for some autoimmune diseases. However, association studies of ITP and CTLA4 gene have obtained conflicting results. This is the first study to systematically investigate the association of CTLA4 with ITP in Chinese Han children.

CONCLUSIONS

The CTLA4 gene is suggested to correlate with ITP through its abnormal expression level instead of gene site mutation.

Splenectomy in haematology–A 5-year single centre experience

OBJECTIVE

To define indications and outcome in haematologic cases undergoing splenectomy.

STUDY DESIGN

A retrospective review of clinical records from consecutive patients having open or laparoscopic removal of the spleen in an academic centre in the private sector. Endpoints were survival, operating time, spleen size, histopathology, requirements for blood or related products complications and average costs.

RESULTS

In the total group (n = 69) there were two deaths. Referrals were for immune thrombocytopaenia (41%), acquired haemolytic anaemia (10%), myeloproliferative syndrome (9%), acute or chronic leukaemia (19%), lymphoma (13%) and a miscellaneous group (8%), comprising cholelithiasis, aplasia or as a diagnostic procedure for otherwise unexplained splenomegaly. An open midline approach was predicated by spleens greater than twice normal size and a history of any bleeding disorder. Here the mean operating time was 83 min (range 40-295) whereas for laparoscopy this was 251 min (range 181-272).

SUMMARY

Careful stratification between the two options facilitated optimum haemostasis and consequently reduced requirement for packed red cells and platelets. Neither underlying pathology nor the choice of treatment influenced morbidity or mortality. Overall local experience is consistent with published international standards of surgical practice. Outcome is directly proportional to the number of each procedure carried out by a single team, observance of consistent protocols for preoperative evaluation and standardized proactive management through the recovery period.

Gammaherpesvirus latency induces antibody-associated thrombocytopenia in mice

Human herpesviruses establish lifelong latency. Viral recrudescence can lead to the development of cancers, immunoproliferative disorders, transplantation complications, and thrombocytopenia. Although platelet-specific autoantibodies have been reported in patients infected with the Epstein-Barr virus (EBV), the mechanisms by which thrombocytopenia is induced remain unclear, as do the relative contributions of lytic viral replication and latent viral gene expression. The human gammaherpesviruses are tightly restricted in their ability to infect other mammals, so they are difficult to study in live animal models. Here we show that infection of mice with murine gammaherpesvirus-68 (γHV68), a rodent-specific pathogen closely related to EBV, induces the production of platelet-binding antibodies and causes thrombocytopenia. Infection of antibody-deficient mice does not lead to thrombocytopenia, indicating the platelet decrease is mediated by antibody. Additionally, infection with a latency-null recombinant γHV68 does not induce thrombocytopenia, suggesting factors associated with viral latency drive the infection-induced antibody-mediated thrombocytopenia. These studies describe an important animal model of gammaherpesvirus-induced autoimmune thrombocytopenia and demonstrate that this pathology is mediated by antibody and dependent on viral latency. This model will allow studies of the underlying mechanisms of disease progression and the testing of therapeutic strategies for the alleviation of virus-induced thrombocytopenia.

Novel clearance mechanisms of platelets

PURPOSE OF REVIEW

Blood platelets are involved in primary and secondary hemostasis and thus maintain the integrity of the vasculature. They circulate with an average lifespan of 5-9 days in humans. Thus, the body must generate and clear platelets daily to maintain normal physiological blood platelet counts. Known platelet clearance mechanisms include antibody-mediated clearance by spleen macrophages, as in immune thrombocytopenia, and platelet consumption due to massive blood loss.

RECENT FINDINGS

New concepts in the clearance mechanisms of platelets have recently emerged. New evidence shows that platelets desialyted due to chilling or sepsis are cleared in the liver by macrophages, that is Kupffer cells, as well as hepatocytes, through lectin-mediated recognition of platelet glycans. On the contrary, platelet-associated antibodies normalize the clearance of platelets in a mouse model for Wiskott-Aldrich syndrome.

SUMMARY

The goal of this review is to summarize the latest findings in platelet clearance mechanisms with a focus on lectin-mediated recognition of platelet glycans. Transfusion medicine and treatments of hematopoietic disorders associated with severe thrombocytopenia may benefit from a better understanding of these mechanisms.

[Inflammatory reactions of the spleen]

Inflammatory reactions of the spleen occur in the context of two pathophysiological settings. First, lymphoid hyperplasia of the spleen can be the result of a principally physiological production of immune effector cells e.g. due to systemic viral infections, autoimmune diseases and acquired or inherited immunodeficiencies. Second, the spleen itself may be the target of a pathological inflammatory reaction; this setting is exemplified by abscess formation due to septicopyemic spread of bacteria and by granulomatous inflammations, e.g. due to tuberculosis or sarcoidosis. Differential diagnostic considerations have to include splenic inflammatory pseudotumors, mycobacterial spindle cell tumors and lymphomas with granulomatous or histiocyte-rich reactive changes.

Splenic macrophages maintain the anti-platelet autoimmune response via uptake of opsonized platelets in patients with immune thrombocytopenic purpura

BACKGROUND

Immune thrombocytopenic purpura (ITP) is an autoimmune disease primarily caused by IgG anti-platelet autoantibodies. Activation of autoreactive CD4(+) T cells upon recognition of cryptic GPIIb/IIIa peptides presented by antigen-presenting cells (APCs) is a critical step for triggering and maintaining the pathogenic anti-platelet autoantibody response.

OBJECTIVES

We investigated which APCs carry the cryptic peptides of GPIIb/IIIa that activate autoreactive CD4(+) T cells in ITP patients.

METHODS

GPIIb/IIIa-reactive T-cell lines generated from ITP patients were cultured with autologous freshly isolated splenic macrophages, B cells or dendritic cells. To further investigate how the macrophages presented the antigenic GPIIb/IIIa peptides, we prepared macrophages from the peripheral blood monocytes of the same patients during remission.

RESULTS

Macrophages induced the proliferation of GPIIb/IIIa-reactive T-cell lines without an exogenous antigen, but B cells and dendritic cells required GPIIb/IIIa peptides to stimulate the T cells. Macrophages derived from peripheral blood during remission required an exogenous antigen to induce the GPIIb/IIIa-reactive T-cell line response, but could elicit a response without added antigen if they were preincubated with platelets from ITP patients with platelet-associated anti-GPIIb/IIIa antibodies or healthy platelets pretreated with ITP platelet eluates. The T-cell response was inhibited by anti-FcgammaRI antibody. Finally, cultured macrophages that captured opsonized platelets promoted anti-GPIIb/IIIa antibody production in mixed cultures of autologous GPIIb/IIIa-reactive T-cell lines and B cells.

CONCLUSIONS

Splenic macrophages that take up opsonized platelets via FcgammaRI are major APCs for cryptic GPIIb/IIIa peptides, and are central to the maintenance of anti-platelet autoantibody production in ITP patients.

Impact of chronic Immune Thrombocytopenic Purpura (ITP) on health-related quality of life: a conceptual model starting with the patient perspective

BACKGROUND

Immune thrombocytopenic purpura (ITP), a condition characterized by autoimmune-mediated platelet destruction and suboptimal platelet production, is associated with symptoms such as bruising, epistaxis, menorrhagia, mucosal bleeding from the gastrointestinal and urinary tracts and, rarely central nervous system bleeding. The aim of this research is to develop a conceptual model to describe the impact of ITP and its treatment on patients' health-related quality of life (HRQoL).

METHODS

A literature search and focus groups with adult ITP patients were conducted to identify areas of HRQoL affected by ITP. Published literature was reviewed to identify key HRQoL issues and existing questionnaires used to assess HRQoL. Focus group transcripts were reviewed, and common themes were extracted by grouping conceptual categories that described the impact on HRQoL.

RESULTS

The literature synthesis and themes from the focus group data suggest that decreased platelet counts, disease symptoms, and treatment side effects influence multiple domains of HRQoL for ITP patients. Key areas affected by ITP and its treatments include emotional and functional health, work life, social and leisure activities, and reproductive health.

CONCLUSION

ITP affects various areas of HRQoL. This conceptual model will help inform the evaluation of therapeutic strategies for ITP.

Laparoscopic splenectomy is a better treatment for adult ITP than steroids — it should be used earlier in patient management. Conclusions of a ten-year follow-up study

BACKGROUND

Laparoscopic splenectomy (LS) has rapidly become the preferred surgical treatment for immune thrombocytopaenic purpura (ITP). The aim of this study was to assess the long-term outcome of laparoscopic splenectomy for adult ITP performed in a single unit.

METHODS

Between 1992 and 2002, 55 patients underwent LS for ITP refractory to medical therapy. These were performed by one surgeon. Long-term outcome data was obtained by case note review and telephone-based questionnaire. Complete remission was defined as a sustained platelet count of >100 x 10(9)/L without further requirement for medical therapy.

RESULTS

Follow-up information was obtained for 40 (73%) out of 55 patients. Overall, 35 (88%) of 40 patients were in complete remission at five-year median follow-up. Five (13%) patients required continued steroid therapy despite LS. Seven (18%) patients reported bleeding problems, in particular bruising. Thirty-five (88%) of 40 patients considered their operation a success. Of these, 16 (46%) patients wished that the operation had been performed earlier in the course of their disease.

CONCLUSIONS

This ten-year experience demonstrates that LS is safe, effective, and yields excellent long-term results for adult ITP, equivalent to results after open splenectomy. Patients' views suggest that laparoscopic splenectomy should be considered sooner in the management of adult ITP, reducing the duration and morbidity of medical treatment.

Effect of bacterial infection on expression of NF-κBP65 after preserved splenic operation in rabbits using microwave coagulation

AIM: To investigate effect and significance of bacterial infection on expression of NF-κBP65 after partial splenectomy of rabbits using microwave coagulation.

METHODS: Japanese white rabbits with large ears were randomly divided into two groups. There were sham group and experiment group,which was alse called partial splenectomy group of rabbits using microwave coagulation. Streptococcus pneumonia suspension was injected into ear veins 1 month after partial splenectomy of rabbits using microwave coagulation and sham operation group. During 48 hours the animal life was observed. The splenic samples weighted and NF-κBP65 count index of expression of residual spleen was detected.

RESULTS: At 48 hours after bacterial injection no rabbit died in two groups. There was no significant difference between splenic qualiyies of two groups. Under microscope the fibrosis was showed in remnant end of spleen coagulated by microwave. NF-κBP65 was mainly stained in cytoplasm or nucleolus. There was no significance difference between NF-κBP65 count index of expression in experiment group and sham group.

CONCLUSION: Splenic injury coagulated by microwave may be restored in short term. Preserved splenic operation using microwave coagulation is a certainly valuable method of operation.

Multi-dysfunctional pathophysiology in ITP

Idiopathic thrombocytopenic purpura (ITP) is an organ-specific autoimmune disorder characterized by a low platelet count and mucocutaneous bleeding. The decrease of platelets is caused by increased autoantibodies against self-antigens, particularly IgG antibodies against GPIIb/IIIa. The production of these autoantibodies by B cells depends on a number of cellular mechanisms that form a network of modulation, with T cells playing a pivotal role in pathophysiology. Delineation of the dysfunction of cellular immunity has recently been attempted. This review will focus on these recent advances applicable to ITP and to highlight how these may translate into novel approaches to treatment in the future. Multi-dysfunction in these networks may include a failure of self-antigen recognition and tolerance, involvement of abnormal cell surface molecules, altered Th1/Th2 cytokine profiles, impaired megakaryocytopoiesis and impaired cell-mediated cytotoxicity. In ITP, multi-step dysfunctions in these networks may take place that finally lead to the occurrence of the disease. Therefore, unveiling these dysfunctions is vital in understanding the pathophysiology of ITP and will finally lead to the development of new therapies to fight the disease.

The Role of Autoreactive T-Cells in the Pathogenesis of Idiopathic Thrombocytopenic Purpura

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease mediated by antiplatelet autoantibodies. The major target of these autoantibodies is a platelet membrane glycoprotein, GPIIb-IIIa, which is a receptor for fibrinogen and other ligands. We recently identified CD4+ T-cells autoreactive to GPIIb-IIIa in ITP patients. These T-cells are considered pathogenic because they help B-cells produce antibodies that bind to normal platelet surfaces. GPIIb-IIIa-reactive T-cells respond to chemically reduced and tryptic peptides of GPIIb-IIIa but not to native GPIIb-IIIa, indicating that the epitopes they recognize are "cryptic" determinants generated at a subthreshold level by the processing of native GPIIb-IIIa under normal circumstances. Although GPIIb-IIIa-reactive T-cells are also detected in healthy individuals, they are activated in vivo only in ITP patients. Activation of GPIIb-IIIa-specific T-cells and the subsequent production of pathogenic anti-GPIIb-IIIa antibodies can be induced by functional antigen-presenting cells in the spleen that present cryptic GPIIb-IIIa peptides to these T-cells. The pathogenic process of ITP can be explained as a continuous loop in which B-cells produce antiplatelet autoantibodies, splenic macrophages phagocytose antibody-coated platelets and present GPIIb-IIIa-derived cryptic peptides, and GPIIb-IIIa-reactive CD4+ T-cells exert their helper activity. Further studies examining the mechanisms that induce the processing and presentation of cryptic peptides derived from the platelet antigen at disease onset will clarify how the pathogenic autoantibody response in ITP is initiated.

Effect of splenectomy on type-1/type-2 cytokine gene expression in a patient with adult idiopathic thrombocytopenic purpura (ITP)

Background

In view of clinical observations and laboratory results that support a central role of the spleen in idiopathic thrombocytopenic purpura (ITP) pathophysiology, we studied the effect of splenectomy on type-1 and type-2 cytokine gene expression in an adult ITP case, refractory to conservative treatment.

Case presentation

The patient was subjected to splenectomy 9 months after the diagnosis with complete response, attaining platelet counts over 150 × 10⁶/L within 10 days after the operation. Two consecutive blood samples were obtained from the patient, 3 and 7 months after the splenectomy for the purposes of this study. A control group consisted of 11 healthy adults. Peripheral blood mononuclear cells were prepared from each blood sample and cultured in vitro for 8 h with the addition of the mitogens phorbol myristate acetate and ionomycin. Total cellular RNA extracted from 10⁶ cells was submitted to semiquantitave reverse transcriptase-polymerase chain reaction (RT-PCR) for the amplification of IL-2, IFN-γ, IL-4, IL-5, and IL-10 metagraphs. The PCR products were run on ethidium-stained agarose gels, photographed and quantified by densitometry.

A steep decrease of type-1 cytokine expression (IL-2, IFN-γ) and their calculated sum expressing Th1 activity was observed at 7 months post-splenectomy compared to 3 months post-splenectomy, in parallel with a rise of platelet count from 190 × 10⁶/L to 265 × 10⁶/L. The change of type-2 cytokine expression (IL-4, IL-5, IL-10) was slight and the Th2 activity (IL-4+IL-5) remained largely unchanged. The Th1/Th2 ratio, that reflects the pathogenic disease-specific T-cell immune deviation, was accordingly reduced 7 months post-splenectomy (Th1/Th2 = 1.3) compared to 3 months (Th1/Th2 = 3.5).

Conclusions

The reduction of the Th1/Th2 cytokine ratio that was observed over time after splenectomy was accompanied by full clinical remission. Nevertheless, the persistence of a type-1 polarization, even after several months following spleen removal, is suggestive of a more basic abnormality of the immune function in these patients.

[Late results of splenectomy in patients with chronic immune thrombocytopenic purpura]

Splenectomy is definitive treatment for idiopathic thrombocytopenic purpura (ITP) because it removes both the sites of autoantibody producing cells and also the major site of platelet destruction. The purpose of this study was to evaluate long term results of splenectomised patients with ITP and to determine predictor factors for good response. A 167 patients with chronic ITP (136 females, 31 males), median aged 35 years (17-74) was splenectomised after 2 to 160 months (Median 12) from diagnosis of ITP. Indications for splenectomy were: 6 weeks of steroid therapy with platelet count below 10 x 10(9)/l or 3 months with platelet count under 30 x 10(9)/l, or treatment with prednisone above 30 mg more of 6 months to increase platelet count over 30 x 10(9)/l, or repeated relapses. Postoperative complications developed in 16 patients (9.5%), 3 of them died (1.8%) due to thromboembolism and 17 patients discontinued later controls. During follow up to 172 months (Median 62) 111/147 splenectomised patients were in remission (75.5%), 99 in complete (above 100 x 10(9)/l), 12 in partial (50-100 x 10(9)/l) and 36 patients (24.5%) were relapsed (below 50 x 10(9)/l). Remission was achieved in 79/88 patients (89.8%) with good response to prednisone before splenectomy toward 32/62 patients (51.6%) with poor response to prednisone (p < 0.01). Remission was obtained in 9/11 patients (81.8%) who responded well to intravenous immune globulin (0.4 g/kg x 5 d) and only in 1/8 who did not (p < 0.05). Higher response rate was achieved in patients under 40 years of age (81.6%) than in older ones (63.4%) (p < 0.05). No difference was shown between sex and time intervals (3, 6, 12, 24, 36 or over 36 months) from diagnosis to splenectomy. Splenectomy is an effective treatment of refractory ITP with response rate of 75.5% after median follow up of 62 months. In our patients better results on splenectomy were associated with age less than 40 years, good responses to steroid, and intravenous immune globulin.

Splenectomy versus medical treatment for idiopathic thrombocytopenic purpura

BACKGROUND

Treatment strategies for idiopathic thrombocytopenic purpura (ITP) are still uncertain and its management is primarily empirical. The aim of this study was to investigate the role of splenectomy in the therapy of ITP and to evaluate whether medical or surgical treatment is superior.

METHODS

Ninety-two patients with ITP were included in the study. All of these patients had medical therapy and 38 of them underwent splenectomy subsequently. Follow-up was completed in 91 patients after a median of 64 months.

RESULTS

Side effects of medical therapy were noticed in 32 patients (35%), whereas after surgery only 2 patients (5%) had minor complications. A complete or partial remission was achieved in 35 patients (92%) after splenectomy, whereas this was achieved in only 27 patients (30%) after medical therapy. On multivariate analysis splenectomy and age were the only significant independent factors for complete and partial remission.

CONCLUSIONS

Splenectomy is highly effective and safe in the treatment of ITP and is superior over medical therapy. These results should stimulate the discussion about splenectomy for ITP, possibly establishing evidence-based guidelines for surgical treatment in hematology.

Thrombopenic purpura induced by a monoclonal antibody directed to a 35-kilodalton surface protein (p35) expressed on murine platelets and endothelial cells

OBJECTIVE

With the aim of obtaining monoclonal antibodies (mAbs) against mouse endothelial surface antigens, immunization of rats with a mouse-derived endothelial cell line (PY4.1) and subsequent hybridoma production were performed.

MATERIALS AND METHODS

One of the mAbs produced by hybridoma EOL5F5 was selected for its surface binding to endothelial cell lines, and identification of the mAb-recognized antigen was performed by immunoprecipitation. Experiments were performed to analyze the effects of EOL5F5 on systemic administration to mice.

RESULTS

EOL5F5-recognized antigen was a single band of 35 kDa under reducing and nonreducing conditions, features that do not match other known differentiation antigens with comparable tissue distribution. In vivo administration of purified EOL5F5 mAb to mice (n = 20) induced intense cutaneous purpura as well as severe but transient thrombocytopenia. Expression of EOL5F5-recognized antigen was detected on platelets from which it immunoprecipitated a moiety of identical electrophoretic pattern in SDS-PAGE, as the one recognized on endothelial cells. Immunohistochemically, EOL5F5-recognized antigen (p35) also was expressed on dermal capillaries, suggesting that, in addition to thrombocytopenia, damaging effects of the antibody on endothelial cells also might cause the observed purpura.

CONCLUSIONS

Our results show induction of thrombocytopenic purpura in mice with an mAb against a single antigenic determinant expressed on both platelets and endothelium. EOL5F5 mAb injection sets the stage for useful experimental models that resemble immune thrombocytopenic purpura.