Medicine and Health Sciences Commons^™

A Delayed H3k27me3 Accumulation After Dna Replication Of Embryonic Stem Cells Opens Chromatin For Lineage Specific Transcription Factors To Bind And Initiate Differentiation, Jingli Cai, Svetlana Petruk, Robyn Sussman, Sina K. Kovermann, Samantha Mariani, Bruno Calabretta, Steven B Mcmahon, Hugh W. Brock, Lorraine Iacovitti, Alexander Mazo

Department of Neuroscience Faculty Papers

Introduction

Pluripotent stem cells (PSCs) have been useful to generate differentiated progenies for cell replacement therapy, and disease models. The Parkinson’s Disease (PD) field was arguably one of the first to have embraced the promise of stem cells. However, regardless of the differentiation protocols used, cultures and grafts continue to contain multiple cell types with midbrain dopamine (mDA) neural progenitors (NPs) and neurons representing only a fraction of total cells in the dish or graft. During cell differentiation, recruitment of transcription factors (TFs) to repressed genes in euchromatin is essential to activate new transcriptional programs, which is impeded by condensed …

Low Level Lead Exposure Impairs Attentional Set Shifting Task Performance Depending Upon Sex And Developmental Periods Of Exposure, L.S. Neuwirth, D.W. Anderson, J. S. Schneider

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Introduction

Exposure to low levels of lead (Pb) impairs a variety of cognitive processes. Although children exposed to Pb developmentally present with a variety of cognitive impairments that include deficits in learning, memory, language, and executive functioning, experimental work on Pb toxicity in rats has focused mostly on learning and memory deficits and less on executive functions. However, detrimental effects on executive functioning could lead to or even underlie a variety of other cognitive problems attributed to Pb exposure. In this study, we examined the ability of Long Evans rats (control and Pb-exposed: 150ppm Pb-acetate in food given perinatally (gestation …

An Assessment Of The Reliability Of Platelet-Associated Flags Generated By The Sysmex Xe-5000 Automated Hematology Analyzer In Detecting Platelet Clumps, Jennifer M. Hawkins, Do, Gene Gulati, Ph.D, Guldeep Uppal, Md, Jerald Z. Gong, Md

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Background

XE-5000 is an automated hematology analyzer utilized by clinical laboratories worldwide to perform CBC and differential leukocyte counts on EDTA-anticoagulated blood specimens. The overall reliability of the results generated by this analyzer has been assessed and found acceptable for clinical use. The CBC results generated on some of the blood specimens are, however, flagged by the analyzer for verification of the result of the flagged parameter by other means. One such parameter of clinical significance is the automated platelet count, which is often unreliable if the blood specimen contains platelet clumps.

Loss Of Expression Of Swi/Snf Chromatin Remodeling Complex Components And Setd2 Are Heterogeneous, Widespread, And Co-Occur In Clear Cell Renal Cell Carcinoma, Wei Jiang, Md, Phd, Essel Dulaimi, Theodore Parsons, Qiong Wang, Karthik Devarajan, Raymond O'Neill, Charalambos C. Solomides, Md, Stephen C Peiper, Phd, Jospeh R. Testa, Robert Uzzo, Haifeng Yang

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Background

The subunits of the SWI/SNF chromatin remodeling complex have one of the highest mutation rate in human cancers (see Figure 1). Polybromo-1 (PBRM1), a subunit of the SWI/SNF complex, is the second most mutated gene (40%) in clear cell Renal Cell Carcinoma (ccRCC). ARID1A, another subunit that competes with PBRM1 for binding to the complex, was infrequently mutated. The protein expressions of BRG1 and BRM (two catalytic subunits of the complex), and SETD2, a histone modifier (10-15% mutation rate), are not known in ccRCC. In this study we examined their protein expressions by immunohistochemistry (IHC) in tissue microarrays (TMAs), …

Phylogenetic Tree Construction And “Truncal Loss” Analysis Reveal Hidden Associations Between Loss Of Protein Expression In Swi/Snf Complex Components And Tumor Stage And Survival In Clear Cell Renal Cell Carcinoma (Ccrcc), Wei Jiang, Md, Phd, Essel Dulaimi, Karthik Devarajan, Qiong Wang, Raymond O'Neill, Charalambos C. Solomides, Md, Stephen C Peiper, Phd, Robert Uzzo, Joseph R. Testa, Haifeng Yang, Phd

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Background

Polybromo-1 (PBRM1), a targeting subunit of the SWI/SNF chromatin remodeling complex, is mutated at a rate of ~40% in clear cell Renal Cell Carcinoma (ccRCC), second only to VHL. Whether its mutation is correlated with tumor stage is controversial. As other components of the SWI/SNF complex were also reported to be mutated in ccRCC, we aim to examine the protein expression patterns of PBRM1, ARID1A, BRG1, and BRM in ccRCC, and to investigate possible association between their loss of expression and tumor stage, as well as survival. We also included a histone modifier, SETD2, which is recently discovered to …

Assessment For Risk Factors Associated With Local Recurrence In Chordoma, John A. Abraham, Md, Wei Jiang, Md, Phd

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Background

Chordoma is a rare but locally aggressive malignant neoplasm showing notochordal differentiation. The clinical differential diagnoses can be extensive, and definitive diagnosis often relies on histopathologic evaluation. Histologically, chordoma shows dual epithelial and mesenchymal differentiation, with various morphologies. Despite surgical resection and use of adjuvant radiation therapy, the local recurrence rate of chordoma remains high. We aim to establish factors associated with the increased risk of recurrence and help guide treatment decisions.

Pathology Encountered During Cadaver Dissection Provides An Opportunity For Integrated Learning And Critical Thinking, Guiyan Zhang, Bruce Fenderson

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Abstract

Cadaver dissection engages medical students in active learning, critical thinking, and problem solving. During dissection, students at SKMC are encouraged to document pathologic findings in their cadavers and discuss the findings with their peers. Here, we describe two cases that provided opportunities for integrating anatomy with pathology and clinical medicine. The first case was a benign ovarian neoplasm. This large pelvic mass displaced the urinary bladder and uterus, and compressed the ureters and rectum. Students discussed clinical complications of this pelvic mass and reviewed pathologic findings that differentiate benign from malignant neoplasms. The second case was breast cancer with …

Age-Related Ebv-Associated Lymphoproliferative Disorder With Widespread Gastrointestinal Involvement And Subsequent Development Of T-Cell Lymphoma, Guldeep Uppal, Md, Alaina Chodoff, Msii, Zi-Xuan Wang, Phd, Jeffrey P. Baliff Md, Jerald Z. Gong, Md

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Background

Age-related EBV-associated lymphoproliferative disorder (AR-EBVLPD) has emerged as a new subset of B-cell lymphoproliferative disorders. We report a unique case of AR-EBVLPD with a widespread gastrointestinal presentation and subsequent transformation to EBV-associated T-cell lymphoma. To our knowledge, this is the first report of a generalized polymorphic extranodal AR-EBVLPD with subsequent transformation to EBV-induced T-cell lymphoma.

Impact Of Preadmission Beta-Blocker Use On Cardiac Abnormalities And In-Hospital Mortality In Patients With Aneurysmal Subarachnoid Hemorrhage, Toshimasa Okabe, Md, Anushya Jeyabalan, Md, Benjamin E. Leiby, Phd, Fred Rincon, Md, Walter K. Kraft, Md

Department of Pharmacology and Experimental Therapeutics Faculty Papers

Introduction:

Various cardiac abnormalities, including dysrhythmias, left ventricular (LV) dysfunction, and myocardial injury, are commonly seen after subarachnoid hemorrhage (SAH). In patients taking a beta-blocker (BB) chronically, the medication is generally discontinued after hospitalization due to the concern of compromising cerebral perfusion. We hypothesized that sudden BB discontinuation might inadvertently lead to an increased incidence of composite cardiac abnormalities and higher in-hospital mortality in patients presenting with nontraumatic SAH.

Seeing Is Believing: Optical Computed Tomography (Oct) And Histologic Analysis To Define Pathophysiology Of “Very”, Very Late Stent Thrombosis Occurring More Than 7 Years After Drug Eluting Stent Implantation, Antony G. Kaliyadan, Md, Alec Vishnevsky, Md, Henry Siu, Md, David Fishman, Md, John Farber, Md, Nicholas Ruggiero Ii, Md, Michael P. Savage, Md

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Case Presentation

• 58-year-old male with prior non-ST elevation MI with PCI performed using a sirolimus eluting stent placed in a large OM1 branch 86 months prior presented with five hours chest pain similar to prior MI >7 years earlier.
• Additional history of hypertension, hyperlipidemia, non-compliance with antiplatelet therapy and active tobacco abuse at time of presentation.
• Patient reported self-discontinuation of medications (aspirin (time unknown), statin, beta blocker) and resumed smoking.
• Clopidogrel was discontinued by his primary physician 97 days prior to presentation
• Initial electrocardiogram revealed a lateral ST elevation MI and the patient was taken to the cardiac catheterization lab …

A Comparison Of The Who 2004 And 2010 Classification Systems In Pancreatic Neuroendocrine Tumors (Pancreatic Net), James P. Casey, Md, Aakanksha Asija, Md, Anthony J. Prestipino, M.D., Jocelyn A. Sendecki, Md, Jonathan Brody, Md, Harish Lavu, Md, Jordan M. Winter, Md, Charles Yeo, Md, Ashwin R. Sama, Md, Madhaven V. Pillai, Md

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Pancreatic NETs are rare tumors with multiple classification systems. Previous classification systems included tumor size, histologic grade, mitoses, Ki67, and metastases. The current WHO 2010 system utilizes mitotic rate and Ki67% to assign a grade. We compared the WHO 2004 and 2010 classification systems in predicting mortality and metastasis.

Pathologic parameters were used to classify 50 cases of Pancreatic NET according to the WHO 2004 and WHO 2010 systems. The relationship between the WHO 2004 and WHO 2010 grading was investigated using an exact Chi squared test. WHO grade categorization was next explored by vital status, by the exact method, …

Succinate Dehydrogenase Deficiency In Sporadic Pituitary Adenomas: A Potential Mechanism For Tumorigenesis, Edward Andrews, Md, Stacey K. Mardekian, Md, Markku Miettinen, Mark T. Curtis, Md

Department of Pathology, Anatomy, and Cell Biology Resident's Posters

In order to determine whether succinate dehydrogenase (SDH) deficiency plays a role in spor-adic, non-familial pituitary adenomas, we analyzed 80 pituitary adenomas for SDH deficiency from patients without familial tumor syndromes or without known SDH deficiency-associated neoplasms. SDH deficiency was determined by immunohistochemical (IHC) stains for SDHB since the loss of any of the four SDH subunits results in the loss of SDHB expression. Three pituitary adenomas showed complete loss of SDHB staining, and of these two also showed loss of SDHA staining. We further characterized these adenomas by looking at Ki67, IGF1R, and 5-hmC levels via IHC. SDHx …

Comparison Of Two Quantitative Image Analysis Systems For Breast Cancer Immunohistochemistry, Reid H. Phillips, Bs, Sue Direnzo, Bs, Charalambos C. Solomides, Md

Department of Pathology Honors Program Student Research Symposium

Automated image analysis systems for breast cancer immunohistochemistry promise efficiency and reliability in the quantification of therapy targets such as the estrogen receptor (ER) or human epidermal growth factor receptor (Her2). Thomas Jefferson University Hospital owns two such systems, the Aperio ScanScope AT (Leica Biosystems) and Ventana iScan Coreo (Roche). A comparison study was performed to determine if choice of system affects target quantification and subsequent clinical tumor classification. Tumor expressions of ER, progesterone receptor (PR), proliferation marker Ki67, and Her2 were quantified with both systems for tissue samples from twenty breast cancer patients. Positive tumor classification was based on …

Evaluating The Utility Of Thyroglobulin Wash Testing In The Management Of Well-Differentiated Thyroid Carcinoma, Katelyn M. Seither, Rossitza Draganova-Tacheva, Md

Department of Pathology Honors Program Student Research Symposium

Introduction

• Thyroid cancer is the most common endocrine neoplasm worldwide, representing 1.7% of new cancer diagnoses and 0.5% of cancer deaths each year (Baldini et al.)
• The majority of thyroid cancers are primary (originating within the gland itself), are well-differentiated, and are derived from follicular epithelial cells
• Papillary thyroid cancer is the most common subtype

70-80% of all thyroid cancers

Peak incidence in women of child-bearing age

Generally indolent behavior, excellent prognosis with total thyroidectomy

30-90% of patients exhibit recurrent or persistent metastasis to the cervical lymph nodes (Torres et al.) and 20% of cases present with occult cancer that …

20 Year-Old Male With Destructive Lesion Of Orbital Roof, Paris A. Barkan, Bs, Lawrence C. Kenyon, Md, Phd

Department of Pathology Honors Program Student Research Symposium

Patient History

Mr. G.R. is a 20-year-old man with no significant past medical history. He presented in July of 2013 with two months of worsening pain over the right orbit. Periorbital edema was also present. Initial treatment with eye drops, antibiotics (erythromycin followed by cephalexin), and steroids (prednisone) failed to control his symptoms.

In October of 2013, CT and MRI scans revealed a permeative destructive lesion centered in the right orbital roof with extension into the superior orbit and the floor of the anterior cranial fossa. There was no abnormal enhancement in the visualized brain parenchyma.

The radiologic appearance of …

Mechanisms That Modify Immune Response In Neonatal Alloimmune Thrombocytopenia, Robert Cooper, Jay H. Herman

Department of Pathology Honors Program Student Research Symposium

What is NAIT?

Neonatal alloimmune thrombocytopenia (NAIT) is a form of fetal and neonatal thrombocytopenia caused by maternal-fetal platelet antigen incompatibility that results in placental transfer of maternal IgG alloantibodies against the platelet antigen. Currently, there are 28 human platelet antigen systems (HPA) that are polymorphisms of various membrane glycoprotein (GP) integrins. The first HPA and most immunogenic was discovered in the 1960’s and is now termed HPA-1, a diallelic system with HPA-1a and HPA-1b on the GPβ3 subunit of the fibrinogen receptor (Murphy). Approximate HPA-1 phenotype frequencies are: homozygous 1a,1a (~70%); heterozygous 1a,1b (~28%); homozygous 1b,1b (~2%).

Typically an …

Hiv Associated Neurocognitive Disorders In An Antiretroviral Therapy Era, Molly Halloran, David S. Strayer, Md, Phd

Department of Pathology Honors Program Student Research Symposium

HIV emerged as a major threat to world health over 30 years ago, and while its effects on the immune system are widely known, HIV also has broad and devastating effects on the nervous system. Despite our potent antiretroviral therapies (ART), these HIV-associated neurocognitive disorders (HAND) continue to afflict HIV infected individuals. With over 33 million people infected worldwide and evidence that neurological damage can accrue in virologically well controlled individuals, HAND is a pressing challenge. Nevertheless, many questions remain unanswered about this spectrum of disorders.

Peripheral T-Cell Lymphoma Arising From Age-Related Ebv-Associated Lymphoproliferative Disorder (Ar-Ebvlpd), Alaina Chodoff, Msii, Guldeep Uppal, Md, Jerald Z. Gong, Md

Department of Pathology Honors Program Student Research Symposium

In the setting of underlying immune suppression, Epstein Barr Virus (EBV) is a well-recognized oncogenic agent that induces the malignant proliferation of B-cells. EBV-lymphoproliferative disorders (LPDs) have recently been linked to immunosenescence. We present a unique case of Age-Related EBV-Lymphoproliferative Disorder (AR-EBVLPD) in a 70 year old female that deviates from the characteristic progression of this disease. Over the course of 18 months, the patient’s clinical condition worsened without a definitive diagnosis to explain the severe, atypical widespread chronic inflammation spanning her gastrointestinal tract, from esophagus to small bowel. The diagnosis of AR-EBVLPD, polymorphic extranodal subtype, was delayed until the …

Haploidentical Hematopoietic Stem Cell Transplantation: Rationale, Development, And Jefferson’S Method, Susan Mcilvaine, Dolores Grosso, Rn, Crnp, Dnp, Beth Colombe

Department of Pathology Honors Program Student Research Symposium

INTRODUCTION

There are many indications for hematopoietic stem cell transplantation. In addition to hematologic malignancies, transplants are performed in certain non-hematologic malignancies, for marrow disorders such as Sickle Cell Anemia, and for various inherited disorders such as SCID. Traditionally, transplants have been performed between donors and recipients that are a complete HLA match (typically matched siblings). That is, patients have identical HLA alleles on both copies of chromosome 6. HLA alleles code for major histocompatibility complex molecules, which are the proteins that cause transplant rejection when a mismatch between donor and recipient is present. Thus, matched transplants have been historically …

The Intersection Between Hpv And Hiv Infections: Is There An Increased Susceptibility To Hiv Acquisition In Hpv-Infected Women?, Montida Fleming, Ba, Fred Gorstein, Md

Department of Pathology Honors Program Student Research Symposium

It has been well documented that HIV infection is associated with HPV infection and the progression to cervical carcinoma. Since the spread of HIV/AIDS epidemic, HPV-related cervical carcinoma had such a high prevalence in HIV-infected individuals that it became established as an AIDS-defining illness. Cervical cancer is the most common AIDS-related malignancy, and the sixth most common presenting AIDS-defining illness in women.¹ Additionally, HIV infection leads to a 5-fold increase in multiple new HPV infections within 6 weeks of seroconversion.² Not only does HIV impact acquisition of HPV at molecular and cellular levels, HIV and HPV viruses interact …

Lead Toxicity: What Is It And How Is It Happening?, Kimberly A. Parada, Ba, Jay S. Schneider, Phd

Department of Pathology Honors Program Student Research Symposium

EPIDEMIOLOGY

Lead poisoning accounts for 0.6% of the global burden of disease.

In Pennsylvania in 2010, 148,751 children under 72 months of age were tested for blood lead levels. Of those children, 19,176 had blood lead levels greater than 5 μg/dl.

• A lower socioeconomic status increases the chances for lead exposure.
• Lead toxicity is an under-appreciated problem that is entirely preventable.

Molecular Profiling Of Patients With Non Small Cell Lung Cancer At Jefferson University Hospital, Erin Bange, Renu Bajaj, Ms, Phd, Cg (Ascp), Cm, Facmg

Department of Pathology Honors Program Student Research Symposium

Companion diagnostics is the use of specific tests whose results are linked to a particular drug. It allows clinicians the ability to better target the mechanism of pathology in the patient and follow it up with a therapy specifically designed to treat the disease process at hand. This approach to medicine has particularly been championed in the field of oncology with the development of such drugs as Zelboraf for the treatment of metastatic melanoma with the BRAFV600 mutation or Xalkori for late stage lung cancer expressing an abnormal ALK protein. In the case of non-small cell lung cancer (NSCLC) Jefferson …

Plasmapheresis And Hiv-Associated Thrombotic Microangiopathy: An Institutional Review, Megan Fisher, Ms2, Nancy Edger Hall, Rn, Mba, Jennifer Webb, Md, Julie Karp, Md

Department of Pathology Honors Program Student Research Symposium

Thrombotic thrombocytopenic purpura (TTP) is a systemic disorder that classically results from a deficiency in the von Willebrand factor-cleaving enzyme, ADAMTS13. The human immunodeficiency virus (HIV) is a secondary cause of TTP. It has been recognized that some patients with HIV-associated TTP do not have a deficiency in ADAMTS13 activity. The role of plasmapheresis (PLEX) in these patients is unclear. This study reviewed 8 cases of HIV-associated TTP at Thomas Jefferson University Hospital. All patients responded to treatment; however, we were unable to make any conclusions regarding the use of PLEX in patients with normal ADAMTS13 activity. HAART initiation is …

Her-2 Heterogeneity In Breast Cancer: A Case Study, Kinnari Patel, Theodore Parsons

Department of Pathology Honors Program Student Research Symposium

CASE

The patient is a 75 year-old female with a history of stage 1 invasive ductal carcinoma of the left breast measuring 1.2 cm. Core biopsy of the mass demonstrated Nottingham grade 3 invasive ductal carcinoma; ER negative, PR negative, HER-2 negative (1+). The patient underwent mastectomy in April 2013. Mastectomy confirmed Nottingham grade 3 invasive ductal carcinoma pT1c/pN0/pMX with peritumoral lymphovascular invasion and invasive tumor less than 1 mm from the superoanterior margin. Due to comorbidities the patient was not considered a candidate for adjuvant chemotherapy.

In January 2014 the patient presented with a mastectomy site recurrence. Needle core …

Personalized Immune Therapy For Cancer A Potential Game-Changing Treatment, Emily Evron, Emanual Rubin, Md

Department of Pathology Honors Program Student Research Symposium

T-CELL RECEPTOR, NORMALLY

T-cell receptors reside on the surface of T-cells, and recognize a specific antigen presented by an MHC molecule

Next, the T-cells become either CD4 or CD8 cells

Co-stimulation is a key step in activating the T-cell; B7 proteins on the surface of antigen-presenting cells interact with CD28/CTLA-4 receptors on the T-cell.

Small Cell Carcinoma Of The Bladder: A Rare Entity, Andrew H. Matthews, Ruth Birbe, Md

Department of Pathology Honors Program Student Research Symposium

BACKGROUND

Primary small cell carcinoma of the urinary bladder is a rare tumor, accounting for less than 1% of the annual 70,000 cases of urinary bladder cancer.¹ Accordingly, little data is available beyond case series to guide diagnosis or treatment. Overall prognosis remains poor with five year survival often markedly below 50%. Current staging and treatment remains largely based on extrapolation from small cell carcinoma of the lung. We review two recent cases of bladder small cell carcinoma with a focus on comparing and contrasting with lung small carcinoma.

Giant Cell Tumor Of Soft Tissue: A Case Study, Rachel Schneider, Brian J. O'Hara

Department of Pathology Honors Program Student Research Symposium

BACKGROUND

Giant cell tumors of soft tissue are relatively uncommon tumors. They are considered to be the soft tissue counterpart to giant cell tumors of bone. Both tumors consist of multi-nucleated giant cells evenly distributed throughout a background of epithelioid mononuclear cells, and are usually benign, but can be locally invasive. Giant cell tumors of soft tissue typically occur in patients over age 40, and show no gender or racial predilection. They present as firm, well demarcated masses, which are not connected to the underlying muscle, tendon, or bone. Giant cell tumors of soft tissue are generally small, and tend …

Small Cell Carcinoma Of The Breast, Victor Carlson, Paolo Cotzia, Md, Juan P. Palazzo, Md

Department of Pathology Honors Program Student Research Symposium

INTRODUCTION

Small cell carcinoma of the breast (SCCB) is a rare, highly aggressive neoplasm first reported in 1983. With striking histologic similarity to small cell carcinoma of the lung, it is comprised of small cells with relatively large, hyperchromatic nuclei and scanty cytoplasm. While capable of hormone secretion, this is a rare occurrence in this variant of small cell carcinoma. Patients typically present with a suspicious breast mass confirmed on imaging, with variable lymph node invasion.

Fibrosing Cholestatic Hepatitis C Post-Liver Transplantation: A Case Study, Layla Hatem, Wei Jiang, Md, Phd

Department of Pathology Honors Program Student Research Symposium

Introduction:

Liver Transplantation:

• Hepatitis C infection is the most common indication for liver transplantation in the US
• HCV infection of the liver allograft occurs within hours from circulating virions.

-Serum RNA levels are observed in the first several weeks.

-Acute hepatitis occurs in 2-6 months

-Chronic hepatitis occurs in 3-9 months

***Persistence of HCV infection is the rule after transplantation due to immune suppression

Chronic recurrent HCV infection post transplantation

• There are four distinct patterns of recurrent chronic HCV in the liver allograft.

-Usual chronic HCV (>70%)

-Fibrosing Cholestatic Hepatitis C (5-10%)

-Plasma cell-rich HCV

-HCV overlapping with rejection …

Interleukin-7-Dependent B Lymphocytes Are Required For The Anti-Pneumococcal Polysaccharide Response And Protective Immunity To Streptococcus Pneumoniae, Gregory S. Dickinson, Phd, Raja Vuyyuru, Timothy L. Manser, Phd, John F. Kerney, Kishore Alugupalli, Phd

Department of Microbiology and Immunology Faculty Papers

Unlike human adults or adult mice, young children or young mice respond poorly to pneumococcal polysaccharides (PPS). In mice, B1b lymphocytes are the major responders to a variety of bacterial polysaccharides including PPS. Despite having B1b cells, young mice are severely impaired in responding to PPS, suggesting that B cells in the young are distinct from those in adults. Since B lymphopoeisis early in life is largely Interleukin-7 (IL-7)-independent, while in adults it is IL-7-dependent, we hypothesize that B cells developed in the presence of IL-7 are required for generating anti-PPS antibody responses. In support of this, we found that …