Parvoviruses and bone marrow failure

Role of clinical, molecular, and serological features in the diagnosis of parvovirus B19 infection in children

BACKGROUND

Parvovirus B19(B19) is a DNA virus. The most common B19 disease is erythema infectiosum (fifth-disease). PCR and ELISA are sensitive for detecting of acute disease. However, it is not clear which test better and the relationship between laboratory tests and clinical findings.

OBJECTIVE

To discuss the clinical and laboratory characteristics of pediatric patients infected with B19.

STUDY DESIGN

236 children were examined. Children with at least one positive molecular or serological test were included. Positive serum B19-DNA and/or B19-IgM was considered an acute B19 infection.

RESULTS

B19DNA was detected in 80.8 % of acute cases. Serological tests were less positive. Acute B19 infection was observed in 24 patients. Only 17 patients were positive for B19 DNA, 3 for IgM and 4 for both. The sensitivity of B19 DNA is 87.5 %. However, this rate is 29.2 % for B19 IgM.

CONCLUSION

B19-DNA and IgM together provide a better, highly accurate diagnosis.

Folate Deficiency and Medication-Induced Severe Pancytopenia in a Bilateral Lung Transplantee

Folate is a water-soluble vitamin that is essential to DNA synthesis and replication. Its deficiency is a leading cause of megaloblastic anemia, which is often asymptomatic but can present with nonspecific symptoms, such as fatigue and lightheadedness. Folate deficiency can rarely present with pancytopenia, which has been described in past case reports but even more scarcely in transplant recipients. We present a 74-year-old bilateral lung transplantee who presented with presyncope and was found to have severe pancytopenia with folate deficiency during the initial workup. Some medications, including mycophenolate mofetil, valganciclovir, and posaconazole were held. Peripheral blood smear showed blastoid cells, but follow-up imaging and flow cytometry negated any concern for a malignant process. Bone marrow biopsy showed an extremely hypocellular marrow with marked trilineage hypoplasia. He required blood product transfusions, but his admission was overall uneventful with no life-threatening sequelae. His blood counts improved with folate replacement and discontinuation of offending medications. He was discharged after nine days in stable condition. Two months later, he experienced a milder and self-limited recurrence of pancytopenia with normal folate and cobalamin levels.

Clinical Signs and Treatment of New-Onset Bone Marrow Failure Associated SARS-CoV-2 Infection in Children: A Single Institution Prospective Cohort Study

Background

Viral infections can cause direct and indirect damage to hematopoietic stem cells. The objectives of this study were to identify the frequency and severity of aplastic anemia in children infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as well as recognize the response to treatment.

Methodology

13 children with newly diagnosed severe aplastic anemia were enrolled in this prospective clinical trial. Blood samples were obtained from all patients to detect SARS-CoV-2 antibodies, and nasopharyngeal swabs were collected for reverse-transcription Polymerase Chain Reaction to detect SARS-CoV-2 viruses. According to the laboratory results, patients were classified as having SARS-CoV-2 positive antibodies and SARS-CoV-2 negative antibodies. Both groups received combined cyclosporine (CsA) + Eltrombopag (E-PAG). The hematological response, either complete response (CR) or partial response (PR), no response (NR), and overall response (OR) rates of combined E-PAG + CsA treatment after 6 months were evaluated.

Results

Four children were recognized to have aplastic anemia and SARS-CoV-2 positive antibodies. Two patients fulfilled the hematological criteria for CR and no longer required transfusion of packed red blood cells (PRBCs) or platelets, and one had PR and was still PRBC transfusion-dependent but no longer required platelet transfusion. The remaining patient showed NR, and he had died before reaching the top of the HSCT waiting list. Moreover, six patients in the SARS-CoV-2 negative antibodies group had CR, while three patients had PR. The difference in ANC, Hg, and platelet counts between both groups was not significant.

Conclusion

The SARS-CoV-2 virus is added to several viral infections known to be implicated in the pathogenesis of aplastic anemia. Studies are needed to establish a definitive association and determine whether the response of bone marrow failure to standard therapy differs from that of idiopathic cases.

Two Cases of Kidney Transplant Recipients With Multiple Relapsing Pure Red Cell Aplasia Due to Parvovirus B19 Infection

Although anemia is common after kidney transplant, pure erythroid aplasia due to parvovirus B19 infection is rare. Therefore, there are delays in diagnosis in transplant patients. Here, we aimed to raise awareness that pure red blood cell aplasia due to parvovirus B19 should be considered in the differential diagnosis of posttransplant anemia. Our report analyzes 2 kidney transplant recipients under immunosuppressive therapy who were diagnosed with pure red blood cell aplasia due to parvovirus B19 infection. Both patients were examined for anemia as a cause for transfusion dependence. Normochromic, normocytic anemia, and reticulocyte levels were low. Leukocyte and platelet counts and biochemical parameters were within reference ranges.Therefore, pure red blood cell aplasia associated with parvovirus B19 was included in the differential diagnosis. Bone marrow showed erythroid hypoplasia and megaloblastic changes with giant erythroblasts containing dark-stained inclusion structures. Results from the other series (neutrophils, lymphocytes, platelets) were within reference ranges. Parvovirus B19 immunoglobulin M and G levels were negative inbothpatients, yet serum parvovirus B19 DNA polymerase chain reaction test results were positive. Therefore, diagnosis was parvovirus B19-associated pure red blood cell aplasia. Anemia resolved completely by 4 weeks after reduction of immunosuppression and intravenous immunoglobulin. Both patients relapsed in month 5 of treatment. One patient relapsed 3 times during follow-up, with complete response to intravenous immunoglobulin for all 3 events.The second patient showed partial response to intravenous immunoglobulin after relapse. We suggest that pure red blood cell aplasia associated with parvovirus B19 should be considered in transplant patients who present with anemia and reticulocytopenia. Negative serology does not exclude thediagnosis, anditis important to perform a parvovirus B19 DNA polymerase chain reaction test. Intravenous immunoglobulin therapy is effective to cure anemia within weeks. Follow-up of patients is important because relapse may occur after treatment.

Intravenous immunoglobulin treatment of congenital parvovirus B19 induced anemia - a case report

BACKGROUND

Parvovirus is a common childhood infection that could be very dangerous to the fetus, if pregnant women become infected. The spectrum of effects range from pure red blood cell aplasia with hydrops fetalis to meningoencephalitis, with many symptoms in between. Severe anemia in the setting of pure red blood cell aplasia is one of the more common effects that neonatal experience (if infected intrapartum), with the current gold standard treatment being intrauterine or postnatal packed red blood cell (PRBC) transfusions, yet intravenous immunoglobulin (IVIG) may be a superior treatment option.

CASE PRESENTATION

A preterm infant was born at 26th week of gestational age via emergency Cesarean section due to hydrops fetalis, with parvovirus B19 exposure one month prior. The infant tested positive for IgM antibodies against parvovirus B19. Among many other serious complications of both hydrops fetalis and premature delivery, the infant had severe unremitting anemia, and received many PRBC transfusion over the course of his 71-day-long neonatal intensive care unit stay. During a follow up appointments as outpatient, his blood tests showed persistent high copies of parvovirus B19. He was then supported with PRBC transfusions and treated with IVIG. After three doses of IVIG, the infant's parvovirus B19 viral copy numbers have dramatically reduced and the infant did not require any more PRBC transfusions.

CONCLUSIONS

IVIG infusion effectively treated the parvovirus B19 infection and restored erythropoiesis making the child transfusion independent. Furthermore, since IVIG is safe and readily crosses the placenta, further studies are needed to determine if IVIG should be considered as an alternative prenatal treatment for congenital parvovirus B19 infection.

A Case of Severe Aplastic Anemia in a 35-Year-Old Male With a Good Response to Immunosuppressive Therapy

Aplastic anemia (AA) is a severe but rare hematologic condition associated with hematopoietic failure leading to decreased or total absent hematopoietic precursor cells in the bone marrow. AA presents at any age with equal distribution among gender and race. There are three known mechanisms of AA: direct injuries, immune-mediated disease, and bone marrow failure. The most common etiology of AA is considered to be idiopathic. Patients usually present with non-specific findings, such as easy fatigability, dyspnea on exertion, pallor, and mucosal bleeding. The primary treatment of AA is to remove the offending agent. In patients in whom the reversible cause was not found, patient management depends on age, disease severity, and donor availability. Here, we present a case of a 35-year-old male who presented to the emergency room with profuse bleeding after a deep dental cleaning. He was found to have pancytopenia on his laboratory panel and had an excellent response to immunosuppressive therapy.

Parvovirus B19 infection in pediatric allogeneic hematopoietic cell transplantation - Single-center experience and review

BACKGROUND

Parvovirus B19 (B19V) infection following pediatric hematopoietic cell transplantation (HCT) is a rare complication and available data is scarce. Therefore, we present the experience with B19V Infection in allogeneic pediatric HCT recipients at our transplant center together with a systematic review of the literature.

METHODS

Pediatric HCT patients with Parvovirus B19 infection treated at the University Children's Hospital Münster between 1999 and 2021 were retrospectively identified and clinical data were analyzed. Additionally, a systematic MEDLINE search to identify relevant articles was performed.

RESULTS

We identified three out of 445 patients (0.6%) with B19V infection post-transplantation. B19V infection occurred in combination with other complications like Graft-versus-Host disease, additional infections, or autoimmune-mediated hemolysis potentially triggered by B19V. In one patient these complications lead to a fatal outcome. The review of the literature showed considerable morbidity of B19V infection with the potential for life-threatening complications. Most patients were treated by red blood cell transfusion and intravenous immunoglobulins (IVIG) with a high succession rate.

CONCLUSION

Symptomatic B19V infection following HCT remains a rare but potentially challenging complication. A causal antiviral therapy does not exist as well as general recommendations on dosage and duration of IVIG therapy. Despite this, most patients are treated successfully with these measures. Additionally, transmission via blood or stem cell products is also rare and no general recommendations on B19V screenings exist.

Treating Parvovirus Triggered Refractory Hemolytic Anemia with Rituximab in Renal Transplant Recipients - A Report of Two Cases

Parvovirus B19 is a small (26 nm), nonenveloped, single-stranded DNA (5.6-kb) virus. The only known host for parvovirus B19 is humans. Parvovirus B19 is directly cytotoxic to erythroid precursor cells of the colony- and burst-forming units. Human parvovirus B19 is the etiologic agent of erythema infectiosum and chronic pure red cell aplasia in immunocompromised individuals. Acute parvovirus B19 infection should be suspected in immunocompromised patients, who present with reticulocytopenic hemolytic anemia and thrombocytopenia. Intravenous immunoglobulin (IVIg) is the standard treatment for parvovirus-induced cytopenias. We report two cases of postrenal transplant who presented with reticulocytopenic anemia and were found to have parvovirus infection. They did not respond to conventional treatment with intravenous gamma globulin. Both patients were treated with rituximab with which they had improvement in clinical and hematological parameters. There was no previous documentation of using rituximab in the treatment of parvovirus-triggered autoimmune hemolytic anemia postrenal transplant patients. This article illustrates how rituximab will be helpful in this setting, of course, it is a new thought but requires further studies and validation.

Aplastic anemia induced by human parvovirus B19 infection in an immunocompetent adult male without prior hematological disorders: A case report

Introduction and importance

Parvovirus B19 (B19V) is a human pathogenic virus of clinical relevance. Human parvovirus B19 infection can be asymptomatic or frequently associated with erythema infectiosum, or joint symptoms in healthy adults. Aplastic anemia as a complication of human parvovirus infection is rare in healthy adults without prior hematological disorders.

Case presentation

We report a case of severe aplastic anemia in a 22-years-old immunocompetent adult male without any hematological dysfunction who presented with periumbilical pain, loose watery stools, and fever with chills and rigor. General examination, laboratory investigation, and peripheral blood smear revealed anemia with leucopenia and relative lymphocytosis, thrombocytopenia, and severe neutropenia. Bone marrow biopsy revealed hypocellular bone marrow with maturation arrest at the proerythroblast stage with intranuclear inclusions and no blast and hematopoietic cells replaced by mature adipocytes in marrow spaces. Parvovirus B19 infection was confirmed by viral serology and polymerase chain reaction.

Clinical discussion

Asymptomatic or mild infection occurs most often when B19 affects immunocompetent adults. However, this is the fourth case reporting severe aplastic anemia in immunocompetent adults and the first case reported in immunocompetent adult males. The patient was admitted for close monitoring and supportive management, which effectively improved the patient's clinical condition, and discharged with a strict follow-up schedule in an outpatient setting.

Conclusion

Thus, acute infection with this virus must be considered a cause of acquired aplastic anemia even in individuals without underlying disease.

•

Erythema infectiosum, often known as the fifth disease is the most common manifestation in children, whereas, in healthy adults, most cases of infection are asymptomatic or associated with arthritis and myalgia.

•The virus causes infections worldwide that vary in severity depending on the age as well as the immunologic and hematologic status of the host.

•Parvovirus infection should be considered as one of the causes of sudden and severe aplastic anemia even in previously hematologically normal individuals with intact immunity.

•Patients should be treated symptomatically until their hematopoiesis restores, and regular follow-up is critical for detecting chronic anemia or recurrence and treating it promptly.

Parvovirus B19 Infection due to over Immunosuppression in Kidney Transplant Recipients: Case Reports and Literature Review

Parvovirus B19 (PB19) is a single-stranded DNA virus that belongs to the Erythrovirus genus within the Parvoviridae family. Clinical presentations associated with PB19 infection vary greatly, depending on the infected individual's age and hematologic and immunologic status. The limited data available regarding consensus on screening algorithms and indications in donors and recipients prior to kidney transplantation makes diagnosis and management challenging. We presented 3 cases of pure red cell aplasia due to parvovirus B19 after kidney transplant. These patients were diagnosed with severe normocytic, normochromic anemia (hemoglobin below 60 g/L) in the 1^st 6 months posttransplant. A complete anemia work-up revealed low reticulocyte count and was otherwise inconclusive. All patients were diagnosed with pure red cell aplasia due to parvovirus B19. Two patients improved after receiving intravenous immunoglobulin 2 gm/kg given over 4 doses. Unfortunately, they relapse after few weeks and required additional doses of intravenous immunoglobulin in conjugation with reduction of their immunosuppressive medication. The third patient improved after holding mycophenolate mofetil (MMF) and did not require intravenous immunoglobulin. Whereas PB19 infection is typically self-limiting and associated with positive IgM serology in immunocompetent hosts, these cases highlight the importance of considering PB19 infection in the differential diagnosis of persistent anemia in immunocompromised patients and the challenges in confirming the diagnosis. Intravenous immunoglobulin (IVIG) can be an effective treatment in immunocompromised patients with primary or relapsed PB19 infection in conjunction with minimizing immunosuppressive medication. Further research and consideration are required to determine appropriate and targeted screening in donors and recipients in the peritransplantation period.

Remodeling of the Bone Marrow Stromal Microenvironment During Pathogenic Infections

The bone marrow (BM) is the primary hematopoietic organ and a hub in which organismal demands for blood cellular output are systematically monitored. BM tissues are additionally home to a plethora of mature immune cell types, providing functional environments for the activation of immune responses and acting as preferred anatomical reservoirs for cells involved in immunological memory. Stromal cells of the BM microenvironment crucially govern different aspects of organ function, by structuring tissue microanatomy and by directly providing essential regulatory cues to hematopoietic and immune components in distinct niches. Emerging evidence demonstrates that stromal networks are endowed with remarkable functional and structural plasticity. Stress-induced adaptations of stromal cells translate into demand-driven hematopoiesis. Furthermore, aberrations of stromal integrity arising from pathological conditions critically contribute to the dysregulation of BM function. Here, we summarize our current understanding of the alterations that pathogenic infections and ensuing inflammatory conditions elicit on the global topography of the BM microenvironment, the integrity of anatomical niches and cellular interactions, and ultimately, on the regulatory function of diverse stromal subsets.

Persistence of Parvovirus B19 in liver from transplanted patients with acute liver failure

Aim: In this study, we investigated the presence of B19V in liver tissues from patients with acute liver failure (ALF) and evaluated the viral activity in infected liver. Methods: Serum and liver samples from 30 patients who underwent liver transplantation for ALF were investigated for B19V infection by real-time PCR, serological tests and examination of B19V mRNA (transcript) expression in the liver. Results: The serum and liver samples from seven patients were B19V DNA positive (10³-10⁵ copies/ml). Most of them presented detectable anti-B19V IgG, indicating persistent infection. B19V mRNA was detected in all patients, demonstrating intra-hepatic replication. Conclusion: B19V infection of the liver during the course of non-A-E ALF suggested a role of B19V, which produced the worst outcome in co-infected patients and in patients with cryptogenic ALF, in liver damage.

Parvovirus B19-associated graft failure after allogeneic hematopoietic stem cell transplantation

Background

Parvovirus B19 (PVB19) infection has been implicated in allograft failure or dysfunction in solid organ transplantation (SOT) and allogeneic hematopoietic stem cell transplantation (allo‐HSCT), but the literature is limited.

Case

Two pediatric patients were diagnosed with PVB19 infection around the time of allo‐HSCT graft failure. Both cases were secondary graft failure and required second allo‐HSCT.

Conclusion

There are many risk factors and potential confounders in determining the exact etiology of graft failure after allo‐HSCT. These two cases highlight the importance of including PVB19 in the diagnostic evaluation for graft failure. PVB19 infection may be an important risk factor for allo‐HSCT graft failure.

(2S,4R)-4-[18F]Fluoroglutamine as a PET Indicator for Bone Marrow Metabolism Dysfunctional: from Animal Experiments to Clinical Application

PURPOSE

Previous reports confirmed that (2S,4R)-4-[¹⁸F]Fluoroglutamine ([¹⁸F]GLN) accumulated in bone and bone marrow. This study investigates the potential of using [¹⁸F]GLN positron emission tomography (PET) to monitor changes of bone marrow activity after chemotherapy (myelosuppression).

PROCEDURES

Bone marrow inhibition model in mice was induced by an intravenous injection of chemotherapy drug (doxorubicin or rituximab) and the inhibition was confirmed by routine blood cell counts. Bone uptakes of these four radiotracers (2-deoxy-2-[¹⁸F]fluoro-D-glucose, [¹⁸F]GLN, 3'-dexoy-3'-[¹⁸F]fluorothymidine ([¹⁸F]FLT), and sodium [¹⁸F]fluoride) in the mice were measured after i.v. injection and dissection of femur and tibia, and the uptakes in bone-only (BO) and bone marrow (BM) were obtained after separating bone from bone marrow. Additionally, six volunteers were recruited and evaluated with [¹⁸F]GLN. The PET-/CT-guided volumes of interests (VOI) in cervical, thoracic, lumbar vertebra, and skull cortical bone were defined as bone marrow or bone for evaluation, respectively.

RESULTS

[¹⁸F]GLN showed a relatively high bone marrow uptake in mice (up to 9.5 ± 1.3 % ID/g) at 1 h after injection, which was 2.1 times that of [¹⁸F]FLT. The [¹⁸F]GLN uptakes in the bone marrow were substantially inhibited by chemotherapy drug. The decrease of [¹⁸F]GLN's bone marrow uptake was consistent with the reduction of white blood cells (myelosuppression). For [¹⁸F]GLN/PET imaging in humans, the SUV_mean value of bone marrow (1 h after i.v. injection) was between 3.1 and 3.6 in the healthy volunteers (n = 3), and between 1.8 and 2.2 (n = 3) (P < 0.001) in myelosuppression patients, showing a clear reduction of bone marrow uptake.

CONCLUSIONS

Dissection experiments in mice showed that [¹⁸F]GLN displayed relatively high bone marrow uptake, and the uptake was sensitive to bone marrow inhibition induced by doxorubicin/rituximab. The same conclusion was confirmed [¹⁸F]GLN/PET imaging in humans. Therefore, [¹⁸F]GLN/PET imaging may be a useful tool to assess reduction of bone marrow activity in cancer patients, who may be at risk of myelosuppression after chemotherapy.

TRIAL REGISTRATION

Approved by Institutional Review Board of Peking University Cancer Hospital (No. 2017KT38). Registered 18 August 2017.

Parvovirus Infection-Related Anemia after Kidney Transplantation

Anemia postkidney transplantation is an important issue which has been correlated with increased hospitalizations and higher mortality. Infections, including those due to parvovirus B19, CMV, and BK virus (polyomavirus), have also been associated with an increased risk of anemia. Here, we present a case of new-onset anemia in a kidney transplant recipient within 3 months of transplant. The patient was found to have multiple viral infections from parvo B19, BK virus, and rhinovirus. The anemia resolved completely after successful reduction in the parvo B19 and BK viral load. Workup for viral infections must be considered in the differential diagnosis of postkidney transplant anemia.

Parvovirus B19 Infection in Human Bone Marrow Mesenchymal Stem Cells Affects Gene Expression of IL-6 and TNF-α and also Affects Hematopoietic Stem Cells Differentiation

Parvovirus B19 (B19V) has been known to induce transient erythroid aplasia, cytopenia and aplastic anemia. This virus persists in bone marrow mesenchymal stem cells (HBMSCs) of some immunocompetent individuals several years after primary infection. In B19V infected erythroid progenitor cells, the virus induces transactivation of Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) gene expression. Due the critical role of HBMSCs in bone marrow niche and inhibitory effect of inflammatory cytokines on hematopoiesis, the aim of this study was to investigate the effect of B19V on IL-6 and TNF-α gene expression intransfected cells. In addition we assessed the clonogenicity potential of cord blood CD34+ stem cells that were co-cultured with infected cells. After 24 h of transfection, quantitative mRNA expression of IL-6 and TNF-α was evaluated and human cord blood CD34+ HSC were cultured with the transfected cells. At the end of 7 days of culture, HSCs colony forming units (CFUs) assay was performed. Our findings demonstrated statistically significant (18.1 and 21.9 fold) increase of TNF-α and IL-6 gene expression respectively and decrease in burst forming unit-erythrocyte (BFU-E) and colony forming unit-erythrocyte (CFU-E) enumeration(p < 0.05). We concluded that, inducing inflammatory cytokines gene expression in B19V-infected HBMSCs might influence on bone marrow microenvironment and hematopoiesis.

Parvovirus B19-triggered Acute Hemolytic Anemia and Thrombocytopenia in a Child with Evans Syndrome

Background

Human parvovirus B19 (HPV-B19) is the etiologic agent of erythema infectiosum, of transient aplastic crises in individuals with underlying chronic hemolytic disorders, and of chronic pure red cell aplasia in immunocompromised individuals.

Case report

We describe a 14-year-old girl with long-standing Evans syndrome, who presented with severe anemia, reticulocytopenia and thrombocytopenia. A bone marrow aspirate revealed severe erythroid hypoplasia along with the presence of giant pronormoblasts, while serological studies and real-time PCR of whole blood were positive for acute parvovirus B19 infection. The patient was initially managed with corticosteroids, but both cytopenias resolved only after administration of intravenous gamma globulin 0.8g/kg.

Conclusion

Acute parvovirus B19 infection should be suspected in patients with immunologic diseases, who present reticulocytopenic hemolytic anemia and thrombocytopenia. In this setting, intravenous gamma globulin is effective for both cytopenias.

How Viruses Contribute to the Pathogenesis of Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, hyperinflammatory syndrome, characterized by the uncontrolled activation of macrophages and T cells, eliciting key symptoms such as persistent fever, hepatosplenomegaly, pancytopenia, hemophagocytosis, hyperferritinemia, and coagulopathy. Viral infections are frequently implicated in the onset of active HLH episodes, both in primary, genetic HLH as in the secondary, acquired form. Infections with herpesviruses such as Epstein-Barr virus and cytomegalovirus are the most common. In autoimmune diseases, a link between viral infections and autoreactive immune responses has been recognized for a considerable time. However, the mechanisms by which viruses contribute to HLH pathogenesis remain to be clarified. In this viewpoint, different factors that may come into play are discussed. Viruses, particularly larger DNA viruses such as herpesviruses, are potent modulators of the immune response. By evading immune recognition, interfering with cytokine balances and inhibiting apoptotic pathways, viruses may increase the host's susceptibility to HLH development. In particular cases, a direct connection between the viral infection and inhibition of natural killer cell or T cell cytotoxicity was reported, indicating that viruses may create immunological deficiencies reminiscent of primary HLH.

The Role of the Bone Marrow Stromal Compartment in the Hematopoietic Response to Microbial Infections

Continuous production of blood cells unfolds within a complex three-dimensional tissue scaffold established by highly organized stromal cell networks of mesenchymal, neural, and vascular origin inside bone marrow (BM) cavities. Collectively, stromal cells have been shown to serve two principal roles; first as primary participants of bone remodeling and metabolism and second as master regulators of different stages of blood cell development and production. Indeed, ample evidence demonstrates that stromal cells can sense and integrate systemic signals to shape hematopoietic responses and that these regulatory mechanisms are subverted in multiple pathologic conditions. Microbial infections are stressors that elicit potent inflammatory reactions and induce substantial alterations of hematopoietic output. Whether the cellular components of the BM stromal microenvironment are targeted by infections and participate in infection-induced hematopoiesis has not been investigated in sufficient detail to date. In this manuscript, we provide a succinct updated overview of the different cell populations that are currently known to form BM stroma. We discuss experimental evidence demonstrating that different stromal components are actively damaged or functionally altered by pathogens and/or ensuing inflammatory signals and review how these effects are known to contribute to the hematologic manifestations observed during infections.

Impact of Viral Infections on Hematopoiesis: From Beneficial to Detrimental Effects on Bone Marrow Output

The ability of the bone marrow (BM) to generate copious amounts of blood cells required on a daily basis depends on a highly orchestrated process of proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs). This process can be rapidly adapted under stress conditions, such as infections, to meet the specific cellular needs of the immune response and the ensuing physiological changes. This requires a tight regulation in order to prevent either hematopoietic failure or transformation. Although adaptation to bacterial infections or systemic inflammation has been studied and reviewed in depth, specific alterations of hematopoiesis to viral infections have received less attention so far. Viruses constantly pose a significant health risk and demand an adequate, balanced response from our immune system, which also affects the BM. In fact, both the virus itself and the ensuing immune response can have a tremendous impact on the hematopoietic process. On one hand, this can be beneficial: it helps to boost the cellular response of the body to resolve the viral infection. But on the other hand, when the virus and the resulting antiviral response persist, the inflammatory feedback to the hematopoietic system will become chronic, which can be detrimental for a balanced BM output. Chronic viral infections frequently have clinical manifestations at the level of blood cell formation, and we summarize which viruses can lead to BM pathologies, like aplastic anemia, pancytopenia, hemophagocytic lymphohistiocytosis, lymphoproliferative disorders, and malignancies. Regarding the underlying mechanisms, we address specific effects of acute and chronic viral infections on blood cell production. As such, we distinguish four different levels in which this can occur: (1) direct viral infection of HSPCs, (2) viral recognition by HSPCs, (3) indirect effects on HSPCs by inflammatory mediators, and (4) the role of the BM microenvironment on hematopoiesis upon virus infection. In conclusion, this review provides a comprehensive overview on how viral infections can affect the formation of new blood cells, aiming to advance our understanding of the underlying cellular and molecular mechanisms to improve the treatment of BM failure in patients.

Agranulocytosis under biotherapy in rheumatoid arthritis: three cases hypothesis of parvovirus B19 involvement in agranulocytosis observed under tocilizumab and rituximab for the treatment of rheumatoid arthritis

Leukopenia is a considerably common complication of tocilizumab [TCZ] and rituximab [RTX] therapy. RTX-induced leukopenia typically exhibits delayed onset. While agranulocytosis has been reported linked to RTX treatment of lymphoma, this complication rarely occurs in rheumatoid arthritis (RA) treatment and, to our knowledge, has never been reported in association with TCZ therapy. We herein report four agranulocytosis cases in three patients, with the first two cases suspected to be secondary to human parvovirus B19 (PVB19) infection. Agranulocytosis manifested in the first patient 2 months following a third RTX course. Bone marrow (BM) polymerase chain reaction (PCR) was positive for PVB19. The patient relapsed after three TCZ courses, with her PCR again positive for PVB19. Both episodes resolved under granulocyte-macrophage colony-stimulating factor (GM-CSF). In the second patient, agranulocytosis manifested after the 74th TCZ course. Bone marrow PCR was positive for PVB19, and the evolution was favorable under intravenous immunoglobulin administration. The third case was a 53-year-old female patient with seropositive RA who presented agranulocytosis after the first infusion of her fourth RTX course. Unfortunately, no PCR PVB19 was made on myelogram. Evolution was favorable after 5 days of GM-CSF. PVB19 infection should be investigated in patients suffering from agranulocytosis manifesting during biotherapy. In cases manifesting from the 15th day of RTX treatment onwards, hemogram must be conducted before readministering the infusion.

Understanding chronic neutropenia: life is short

The pathophysiological mechanisms underlying chronic neutropenia are extensive, varying from haematopoietic stem cell disorders resulting in defective neutrophil production, to accelerated apoptosis of neutrophil progenitors or circulating mature neutrophils. While the knowledge concerning genetic defects associated with congenital neutropenia or bone marrow failure is increasing rapidly, the functional role and consequences of these genetic alterations is often not well understood. In addition, there is a large group of diseases, including primary immunodeficiencies and metabolic diseases, in which chronic neutropenia is one of the symptoms, while there is no clear bone marrow pathology or haematopoietic stem cell dysfunction. Altogether, these disease entities illustrate the complexity of normal neutrophil development, the functional role of the (bone marrow) microenvironment and the increased propensity to undergo apoptosis, which is typical for neutrophils. The large variety of disorders associated with chronic neutropenia makes classification almost impossible and possibly not desirable, based on the clinical phenotypes. However, a better understanding of the regulation of normal myeloid differentiation and neutrophil development is of great importance in the diagnostic evaluation of unexplained chronic neutropenia. In this review we propose insights in the pathophysiology of chronic neutropenia in the context of the functional role of key players during normal neutrophil development, neutrophil release and neutrophil survival.

Parvovirus B19 infection presenting with severe erythroid aplastic crisis during pregnancy in a woman with autoimmune hemolytic anemia and alpha-thalassemia trait: a case report

Introduction

Parvovirus B19 virus commonly causes subclinical infection, but it can prove fatal to the fetus during pregnancy and cause severe anemia in an adult with hemolytic diseases. We present the case of a woman with autoimmune hemolytic anemia who was diagnosed with parvovirus B19-induced transient aplastic crisis during her second trimester of pregnancy and faced the high risk of both fetal and maternal complications related to this specific viral infection. To the best of our knowledge, the experience of successful intravenous immunoglobulin treatment for B19 virus infection during pregnancy, as in our case, is limited.

Case presentation

A 28-year-old and 20-week pregnant Chinese woman with genetically confirmed alpha-thalassemia trait was diagnosed with cold antibody autoimmune hemolytic anemia and suffered from transient aplastic crisis caused by B19 virus infection. She received intravenous immunoglobulin treatment to reduce the risk of hydrops fetalis. Her peripheral blood reticulocyte percentage recovered, but anemia persisted, so she underwent several courses of high dose intravenous dexamethasone for controlling her underlying hemolytic problem. Finally, her hemoglobin levels remained stable with no need of erythrocyte transfusion, and a healthy baby boy was naturally delivered.

Conclusions

Parvovirus B19 virus infection should be considered when a sudden exacerbation of anemia occurs in a patient with hemolytic disease, and the possible fetal complications caused by maternal B19 virus infection during pregnancy should not be ignored. Close monitoring and adequate management can keep both mother and fetus safe.

Acute human parvovirus b19 infection: cytologic diagnosis

Human parvovirus B19 is highly tropic to human bone marrow and replicates only in erythroid progenitor cells. It is causative agent of transient aplastic crisis in patients with chronic haemolytic anemia. In immunocompromised patients persistent parvovirus B19 infection may develop and it manifests as pure red cell aplasia and chronic anaemia. Bone marrow is characterised morphologically by giant pronormoblast stage with little or no further maturation. We encountered a case of 6 year old HIV positive male child presented with pure red cell aplasia due to parvovirus B19 infection. Bone marrow aspiration cytology revealed giant pronormoblast with prominent intranuclear inclusions led to suspicion of parvovirus B19 infection which was confirmed by DNA PCR. This case is presented to report classical morphological features of parvovirus B19 infection rarely seen on bone marrow examination should warrant the suspicion of human parvovirus B19 infection in the setting of HIV positive patient with repeated transfusions and confirmation should be done by PCR.

Dynamics of Graft Function Measured by DNA-Technology in a Patient with Severe Aplastic Anemia and Repeated Stem Cell Transplantation

Although bone marrow transplantation (BMT) from an HLA identical sibling is considered as treatment of choice in pediatric patients with severe aplastic anemia (SAA), a significant number of them experience graft failure (GF) after BMT. We report a case of an 8-year-old male patient with SAA who presented with a complicated posttransplant course due to parvovirus B19 infection and GF. A subsequent attempt to support the graft by antithymocyte globulin (ATG) and a peripheral stem cell boost resulted in transitory autologous recovery of hematopoiesis followed by mixed chimerism, supported by donor lymphocyte infusions (DLIs) and finally graft rejection with relapse of SAA. Permanent complete chimerism was achieved by a second BMT. Dynamics of graft function, measured by a single nucleotide polymorphism (SNPs) analysis, are discussed.

Human parvovirus B19 infection in a renal transplant recipient: a case report

Background

Parvovirus B19 presents tropism for human erythroid progenitor cells, causing chronic anemia in organ transplant recipients, due to their suppressed humoral and cellular responses. Diagnosis may be achieved through serological tests for detection of anti-B19 antibodies. However, renal transplant recipients are not routinely tested for parvovirus B19 infection, since there is scanty data or consensus on screening for B19 infection, as well as for treatment or preventive management of transplanted patients.

Case presentation

Herein we report a kidney transplant recipient, who was unresponsive to treatment of severe anemia, and presented hypocellular hematopoietic marrow, megaloblastosis and hypoplasia of erythroid lineage with larger cells with clear nuclei chromatin and eosinophilic nuclear inclusions. This patient was seropositive for Epstein-Barr and Cytomegalovirus infections and negative for anti-parvovirus B19 IgM and IgG antibodies, although symptoms were suggestive of parvoviruses infection. A qualitative polymerase chain reaction testing for B19 in serum sample revealed positive results for B19 virus DNA.

Conclusion

This case report suggests that the diagnostic process for parvovirus B19 in renal transplant recipients should include a polymerase chain reaction assay to detect B19-DNA, since specific serological tests may be unreliable given their impaired humoral responses. These results also indicate the importance of considering parvovirus B19 infection in the differential diagnosis of persistent anemia in transplanted patients.

The differential diagnosis and bone marrow evaluation of new-onset pancytopenia

New-onset pancytopenia can be caused by a wide variety of etiologies, leading to a diagnostic dilemma. These etiologies range from congenital bone marrow failure to marrow space-occupying lesions, infection, and peripheral destruction, to name a few. Bone marrow examination, in addition to a detailed clinical history, is often required for an accurate diagnosis. The purpose of this review is to provide a brief overview of many of the causes of new-onset pancytopenia in adults and children, with emphasis on bone marrow findings and recommendations of additional testing and clinical evaluation when needed, with the overall aim of aiding the pathologist's role as a consultant to the patient's treating physician.

Pure red cell aplasia associated with cytomegalovirus and Epstein-Barr virus infection in seven cases of Chinese children

Pure red cell aplasia (PRCA) associated with cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infection is uncommon. Here, we describe the clinical features and management of seven cases of Chinese children with PRCA associated with viral infections. The patients presented with pallor on admission. Blood cell counts and marrow smears showed anemia, reticulocytopenia, and aplasia of erythroblasts. Serological investigation and DNA polymerase chain reactions for CMV were positive in four patients and those tests for EBV were positive in other three patients. All patients received blood transfusion, corticosteroids treatment, and ganciclovir injection. Two patients had a complete response and one had a partial response after the treatments. The other three patients had a complete response to second-line therapies, including high-dose methylprednisolone, cyclosporin A, and intravenous immunoglobulin. Only one patient had no response to the therapies. Our results indicated that it might be important to combine immunosuppressive drugs with an antiviral drug in the management of PRCA associated with CMV and EBV infection.

Pure red cell aplasia in a simultaneous pancreas-kidney transplantation patient: inside the erythroblast

A case of pure red cell aplasia in a simultaneous kidney-pancreas transplant recipient on immunosuppressive therapy is reported here. The patient presented with anemia unresponsive to erythropoietin treatment. Bone marrow cytomorphology was highly suggestive of parvovirus pure red cell aplasia, which was confirmed with serology and polymerase chain reaction positive for parvovirus B19 DNA in peripheral blood. After the administration of intravenous immunoglobulin the anemia improved with a rising number of the reticulocytes.

Study on clinical characteristics and follow-up visit of acquired aplastic anemia associated with parvovirus B19 infection

OBJECTIVE

To investigate clinical characteristics of parvovirus (B19) related aplastic anemia (AA).

METHODS

Of the 28 children with AA included in this study, 24 were treated routinely and received planned follow-up; 15 were subject to B19-DNA re-examination during the treatment and 8 underwent examination for B19-IgM and B19-IgG. Another 39 initially identified AA children were enrolled as the controls and received the treatment same as the above-mentioned group.

RESULTS

There were more patients aged 5-8 y in the B19 infection group than the control group (P < 0.05). The course of AA in the B19 infection group was less than 2 mo and the serious aplastic anemia (SAA) and very serious aplastic anemia (VSAA) were more frequently observed in this group than the controls (P < 0.05). The overall efficacy of the treatments in the B19 infection group was more dismal than that in the controls (P < 0.05). Among 15 patients who were subjected to B19-DNA re-examination, negative findings were found in 6 patients with chronic aplastic anemia (CAA); the B19-DNA was persistently positive in 2 of the SAA and 5 VSAA patients. IgM and IgG were respectively detected in 3 and 2 patients out of the 8 children who received antibody examination.

CONCLUSIONS

Parvovirus B19 infection contributes to the generation of AA, particularly in children aged 5-8 y. The AA induced may be mainly classified as serious and very serious type, with a course of disease less than 2 mo. Patients can be saved if B19-DNA is eliminated and the antibody is produced.

Concise review: Anemia caused by viruses

Most of the viruses known to be associated with anemia in human tend to persistently infect their host and are noncytopathic or poorly cytopathic for blood cell progenitors. Infections with Epstein-Barr virus, cytomegalovirus, varicella-zoster virus, human herpes virus 6 (HHV-6), B19 parvovirus, human immunodeficiency virus, hepatitis A and C viruses and the putative viral agent associated with non-A-G post-hepatitis aplastic anemia have been reported in association with anemia. Nevertheless, a direct cytotoxic effect on erythroid progenitors has been clearly demonstrated only for human parvovirus B19 and evocated for HHV-6. A major role for destructive immunity is strongly suspected in the pathogenesis of anemia associated with the other viral infections. Host genes play a role in the occurrence of virus-induced anemia in animal models, and there are some evidences that genetic background could also influence the occurrence of virus-associated anemia in human.

Pure red cell aplasia associated with cytomegalovirus infection

A 3-month-old boy presented with progressive pallor since the age of 1 month. Hemogram and bone marrow aspirate were suggestive of pure red cell aplasia. Serum bilirubin and aminotransferases were elevated. Cytomegalovirus serology and DNA polymerase chain reaction were positive. Fetal hemoglobin was normal and Parvovirus B19 DNA polymerase chain reaction was negative. Through this case report, we wish to highlight a rare, might be causative association of cytomegalovirus infection with pure red cell aplasia.

Thrombocytopenia and anemia in infants and children

Thrombocytopenia and anemia are the two most common hematologic conditions seen in the pediatric emergency department. Providers of emergency pediatric care must have an understanding of the causes and therapies for the various conditions that result from thrombocytopenia and anemia. This article reviews the common causes of isolated thrombocytopenia and anemia in infancy and childhood.

Ablation of Gata1 in adult mice results in aplastic crisis, revealing its essential role in steady-state and stress erythropoiesis

The transcription factor Gata1 is expressed in several hematopoietic lineages and plays essential roles in normal hematopoietic development during embryonic stages. The lethality of Gata1-null embryos has precluded determination of its role in adult erythropoiesis. Here we have examined the effects of Gata1 loss in adult erythropoiesis using conditional Gata1 knockout mice expressing either interferon- or tamoxifen-inducible Cre recombinase (Mx-Cre and Tx-Cre, respectively). Mx-Cre-mediated Gata1 recombination, although incomplete, resulted in maturation arrest of Gata1-null erythroid cells at the proerythroblast stage, thrombocytopenia, and excessive proliferation of megakaryocytes in the spleen. Tx-Cre-mediated Gata1 recombination resulted in depletion of the erythroid compartment in bone marrow and spleen. Formation of the early and late erythroid progenitors in bone marrow was significantly reduced in the absence of Gata1. Furthermore, on treatment with a hemolytic agent, these mice failed to activate a stress erythropoietic response, despite the rising erythropoietin levels. These results indicate that, in addition to the requirement of Gata1 in adult megakaryopoiesis, Gata1 is necessary for steady-state erythropoiesis and for erythroid expansion in response to anemia. Thus, ablation of Gata1 in adult mice results in a condition resembling aplastic crisis in human.

Emergent Fetal Intracardiac Transfusion for Thrombocytopenia and Acute Hypovolemia due to Cordocentesis-Associated Hemorrhage in Parvovirus-Induced Hydrops

OBJECTIVES

To demonstrate the utility of fetal intracardiac transfusion to correct acute fetal hypovolemia and thrombocytopenia in fetal Parvovirus infection.

METHODS

Intracardiac transfusion in a 19-week gestation was indicated due to cordocentesis-associated hemorrhage.

RESULTS

Intracardiac transfusion resulted in correction of acute bradycardia, anemia and thrombocytopenia and persistent umbilical cord hemorrhage following attempted intravascular transfusion.

CONCLUSIONS

This case illustrates the importance of anticipating both thrombocytopenia and anemia in fetal Parvovirus infection and how an intracardiac approach can be employed in the setting of acute, life-threatening hemorrhage.

Metastatic basal cell carcinoma: complete response to chemotherapy and associated pure red cell aplasia

Basal cell carcinoma (BCC) is usually a benign and indolent cancer cured in greater than 95 percent of cases. Nevertheless, it can be locally destructive or occasionally metastasize to distant organs. We report a case of BCC metastatic to the lungs, occurring 17 years after the primary BCC was noticed, that responded to carboplatin and paclitaxel on 3 occasions. The patient also developed pure red cell aplasia (PRCA). Work-up did not reveal underlying thymoma or infectious, rheumatologic, or lymphoproliferative disorders. Parvovirus serologies were negative, and antibodies against erythropoetin were not detected. There was no history of exposure to drugs associated with PRCA. Bone marrow biopsy on 2 different occasions did not show evidence of myelodysplasia. PRCA may represent an unusual paraneoplastic syndrome associated with BCC as reported with other carcinomas. This is the first report of PRCA associated with metastatic BCC or the drugs carboplatin and paclitaxel, which were used to treat it. The literature on chemotherapy for metastatic BCC is reviewed.

[A case of systemic lupus erythematosus accompanied with pure red cell aplasia]

Pure red cell aplasia (PRCA) is a rare cause of anemia associated with SLE. We herein report a case presenting with SLE and PRCA. A 33-year-old woman, who had been suffering from photosensitivity, proteinuria, and pancytopenia, was diagnosed to have SLE. She showed normochromatic normocytic anemia. The serum level of haptoglobin was <10 mg/dl, and Direct Coombs' test was negative. Her reticulocyte count was 0.8%. Her clinical and laboratory features, except for anemia, had recovered in response to 50 mg/day of prednisolone. The serum level of haptoglobin had normalized, but the reticulocyte count remained low. The bone marrow findings revealed erythroid hypoplasia, and she was diagnosed to have PRCA complicated with SLE. No viral DNA of human parvovirus B19 in her bone marrow was detected. The anemia gradually improved following the further use of 50 mg/day prednisolone. In order to disclose the mechanism of PRCA in this patient, we examined the effects of her peripheral T lymphocytes on erythrogenesis, using erythroid colony-forming cells (ECFC) in her peripheral blood. When we co-cultured peripheral T cells and ECFC, her T cells inhibited erythroid colony formation in a dose dependent manner. Several reports have shown the presence of inhibitory factors in SLE patients' serum such as antibodies against erythroid progenitors or erythropoietin, while other reports have shown abnormal T cells that inhibit the growth of erythroid progenitors. Our study suggests that these inhibitory T cells may therefore have played an important role in the pathogenesis of this patient.

Human parvovirus B19 associated with idiopathic thrombocytopenic purpura

Although human parvovirus B19 (PVB19) is mainly known to be the causative agent of fifth disease, it is also important in the etiopathogenesis of various hematologic disorders. Recently, its role in the occurrence of chronic anemia and pancytopenia in immunocompromised patients has been revealed. In this study, the authors searched for the presence of PVB19 in a group of patients with idiopathic thrombocytopenic purpura (ITP). The PVB19 DNA was determined by nested PCR, and serologic responses to the virus were evaluated by ELISA. Viral genome was detected by PCR in the sera of 9 of the 19 patients. The IgM and IgG positivities were 57 and 73% in the patients, respectively. These results suggest that PVB19 is associated with ITP nearly in half of the patients and its pathogenetic role in the cases of ITP needs further consideration.

Maternal and fetal inflammatory responses in unexplained fetal death

OBJECTIVE

The role of intra-amniotic infection in the etiology of fetal death has been proposed. This study was conducted to determine the prevalence of microbial invasion of the amniotic cavity (MIAC) and the frequency of maternal and/or fetal inflammation in patients presenting with a fetal death.

METHODS

A prospective study was conducted in patients with a fetal death. Amniocenteses were performed for clinical indications (karyotype), as well as to assess the microbiological and cytological state of the amniotic cavity. Fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas. An amniotic fluid white blood cell count and glucose determinations were also performed. Histological examination of the placenta was conducted to identify a maternal inflammatory response (acute chorioamnionitis) or a fetal inflammatory response (funisitis).

RESULTS

This study included 44 patients with intrauterine fetal death. The median gestational age at diagnosis was 30.1 weeks (range 16.3-40.4 weeks). One patient had documented MIAC (1/44). Acute histological chorioamnionitis was found in 20.9% (9/43), but a fetal inflammatory response was observed in only 2.3% (1/43) of cases. One patient had a positive amniotic fluid culture for Streptococcus agalactiae (group B streptococcus).

CONCLUSION

Histological chorioamnionitis was present in 20.9% of cases, but MIAC could be demonstrated with conventional microbiological techniques in only one case. A fetal inflammatory response was nine times less frequent than a maternal inflammatory response (maternal 20.9% vs. fetal 2.3%, p = 0.008) in cases of fetal death.

Pure red cell aplasia due to parvovirus following treatment with CHOP and rituximab for B-cell lymphoma

A 26-year-old woman, diagnosed with diffuse large B-cell lymphoma, was treated with CHOP (cyclophosphamide, hydroxydaunomycin, oncovin, prednisone), rituximab and radiotherapy. She developed transfusion-dependant anaemia, which persisted following chemotherapy. Bone marrow aspirate and biopsy were consistent with pure red cell aplasia and parvovirus infection. Serology was negative for previous or acute infection but parvovirus DNA was detected by polymerase chain reaction. Administration of intravenous immunoglobulin (1 g/kg) resulted in reticulocytosis and recovery of her haemoglobin. We hypothesize that rituximab caused depletion of her normal B cells, resulting in an inability to mount a primary immune response to parvovirus infection.

Human parvovirus B19 induces cell cycle arrest at G(2) phase with accumulation of mitotic cyclins

Human parvovirus B19 infects specifically erythroid progenitor cells, which causes transient aplastic crises and hemolytic anemias. Here, we demonstrate that erythroblastoid UT7/Epo cells infected with B19 virus fall into growth arrest with 4N DNA, indicating G(2)/M arrest. These B19 virus-infected cells displayed accumulation of cyclin A, cyclin B1, and phosphorylated cdc2 and were accompanied by an up-regulation in the kinase activity of the cdc2-cyclin B1 complex, similar to that in cells treated with the mitotic inhibitor. However, degradation of nuclear lamina and phosphorylation of histone H3 and H1 were not seen in B19 virus-infected cells, indicating that the infected cells do not enter the M phase. Accumulation of cyclin B1 was persistently localized in the cytoplasm, but not in the nucleus, suggesting that B19 virus infection of erythroid cells raises suppression of nuclear import of cyclin B1, resulting in cell cycle arrest at the G(2) phase. The B19 virus-induced G(2)/M arrest may be the critical event in the damage of erythroid progenitor cells seen in patients with B19 virus infection.

Association of parvovirus B19 with plasma cell-rich myocardial infiltrates after heart transplantation

In this report we describe the development of plasma cell-rich myocardial infiltrates in association with a parvovirus B19 infection in a heart transplant patient. We hypothesize that the virus, either alone or in association with the cardiac allograft, may polarize the immune response in the direction of T helper 2 (Th2) cells rather than the expected Th1 cells. This favors the development of a humoral immune response and infiltration of the graft with plasma cells.