Michelle Ratliff

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The oxidative cleavage of heme to release iron is a mechanism by which some bacterial pathogens can utilize heme as an iron source. The pigA gene of Pseudomonas aeruginosa is shown to encode a heme oxygenase protein, which was identified in the genome sequence by its significant homology (37%) with HemO of Neisseria meningitidis. When the gene encoding the(More)
B cell function with age is decreased in class switch recombination (CSR), activation-induced cytidine deaminase (AID), and stability of E47 mRNA. The latter is regulated, at least in part, by tristetraprolin (TTP), which is increased in aged B cells and also negatively regulates TNF-α. In this study, we investigated whether B cells produce TNF-α, whether(More)
Long-lived plasma cells (PCs) and memory B cells (B(mem)) constitute the cellular components of enduring humoral immunity, whereas short-lived PCs that rapidly produce Ig correspond to the host's need for immediate protection against pathogens. In this study we show that the innate affinity of the BCR for Ag imprints upon naive B cells their differentiation(More)
Pseudomonas aeruginosa exports a number of hydrolytic enzymes and toxins using the type II or general secretion pathway, found in a variety of Gram-negative bacteria and requiring the functions of at least 12 gene products (XcpP-Z and PilD/XcpA in P. aeruginosa). A number of these gene products are homologues of components of the type IV pilus biogenesis(More)
CONTEXT Arterial grafts are thought to be better conduits than saphenous vein grafts for coronary artery bypass grafting (CABG) based on experience with using the left internal mammary artery to bypass the left anterior descending coronary artery. The efficacy of the radial artery graft is less clear. OBJECTIVE To compare 1-year angiographic patency of(More)
We recently reported that the transcription factor ARID3a is expressed in a subset of human hematopoietic progenitor stem cells in both healthy individuals and in patients with systemic lupus erythematosus. Numbers of ARID3a(+) lupus hematopoietic stem progenitor cells were associated with increased production of autoreactive Abs when those cells were(More)
Aged mice exhibit ~ 5-10-fold increases in an ordinarily minor CD21/35(-) CD23(-) mature B-cell subset termed age-associated B cells (ABCs). ABCs from old, but not young, mice induce apoptosis in pro-B cells directly through secretion of TNFα. In addition, aged ABCs, via TNFα, stimulate bone marrow cells to suppress pro-B-cell growth. ABC effects can be(More)
In aged mice, new B-cell development is diminished and the antibody repertoire becomes more autoreactive. Our studies suggest that (i) apoptosis contributes to reduced B lymphopoiesis in old age and preferentially eliminates those B-cell precursors with higher levels of the surrogate light chain (SLC) proteins (λ5/VpreB) and (ii) λ5(low) B-cell precursors(More)
In young adult BALB/c mice, antibodies to phosphorylcholine (PC) bearing the T15 (TEPC 15) idiotype confer protection against pneumococcal infections. In old age, even though PC reactive B cells are often increased, the proportion of T15+ antibodies declines. We hypothesize that limited surrogate light chain (SLC) and compromise of the pre-B cell receptor(More)
Although hematopoietic stem/progenitor cells (HSPCs) are used for transplantation, characterization of the multiple subsets within this population in humans has lagged behind similar studies in mice. We found that expression of the DNA-binding protein, ARID3a, in mouse stem cells was important for normal development of hematopoietic lineages; however,(More)