CD8 T cells contain a distinct subset of CD8+ CD28- cells. These cells are not present at birth and their frequency increases with age. They frequently contain expanded clones using various TCRalphabeta receptors and these clones can represent >50% of all CD8 cells, specially in old subjects or patients with chronic viral infections such as HIV-1. Herein, it is shown that a large fraction of CD8+ CD28- cells expresses intracellular perforin by three-color flow cytometry, in particular when this subset is expanded. Together with their known ability to exert potent re-directed cytotoxicity, this indicates that CD8+ CD28- T cells comprise cytotoxic effector cells. With BrdU labeling, we show that CD8+ CD28- cells derive from CD8+ CD28+ precursors in vitro. In addition, sorted CD8+ CD28+ cells gave rise to a population of CD8+ CD28- cells after allo-stimulation. Moreover, ex vivo CD8+ CD28+ cells contain the majority of CD8 blasts, supporting the notion that they contain the proliferative precursors of CD8+ CD28- cells. CD95 (Fas) expression was lower in CD8+ CD28- cells, and this subset was less prone to spontaneous apoptosis in ex vivo samples and more resistant to activation-induced cell death induced by a superantigen in vitro. Thus, the persistence of expanded clones in vivo in the CD8+ CD28- subset may be explained by antigen-driven differentiation from CD8+ CD28+ memory precursors, with relative resistance to apoptosis as the clones become perforin(+) effector cells.

A nti-␥ -globulins or rheumatoid factors (RF) were first described in the early 1940s. They are present in Ͼ 70% of patients with rheumatoid arthritis (RA) and high titers are associated with severe disease, but they also appear in a large number of other diseases including viral, bacterial, and parasitic infections (1). In spite of their wide spread occurrence, it is still a puzzle how or why RF are generated.RF come in two varieties. Low affinity RF (K d of ‫ف‬ 10 Ϫ 5 M) are IgM natural antibodies with specificity for IgG-Fc determinants and cross-reactivity with other autoantigens, i.e., polyreactivity. They are produced by CD5 ϩ B cells in normal subjects (2). Frequently they are IgM antibodies and use selected germline V genes for both H and L chains. This is why they share cross-reactive idiotypes, as discovered by Kunkel et al. in the 1970s (3). These antibodies are typically T cell independent. They are similar to the RF produced in response to polyclonal B cell activation by EBV (4) or LPS (5, 6). B cells producing these RF appear to be susceptible to malignant transformation as the RF-associated V genes are frequently expressed in low grade chronic B lymphoproliferative diseases such as chronic lymphocytic leukemia, Waldenstrom's macroglobulinemia, mixed cryoglobulinemia and lymphoma associated with Sjögren's disease. This may be due to constitutive expression of STAT3 in B1 cells (7). The RF-associated V genes are also over-expressed by human fetal B cells (8, 9), perhaps consistent with a role for low affinity RF in neonates that lack a mature humoral immune system. In spite of the low affinity, the multivalency of IgM RF allows excellent agglutination of latex particles or red blood cells, and presumably also microbial organisms, in vivo, that are coated with specific IgG antibodies. The presence of IgM RF can lead to large immune complexes with lattice formation, that are poorly soluble and rapidly removed by the mononuclear phagocyte system (10).High affinity RF (K d of ‫ف‬ 10 Ϫ 7 M) can be IgM, IgG, IgA, or IgE antibodies. RA patients may have high titers of this type of RF. Their production is T cell dependent. These antibodies often do not share the V genes used by the low affinity RF (11). They have undergone affinity maturation, as there are multiple somatic mutations in the V genes, and are therefore produced by antigen driven B cells. These RF bind most avidly to the Ig isotype which stimulated their production. In RA, RF are particularly abundant in the synovium. In some reports the dominant specificity of synovial RF is for IgG3-Fc (12), implying that the

Peripheral arterial disease (PAD) is a leading cause of limb loss and mortality worldwide with limited treatment options. Mesenchymal stromal cell (MSC) therapy has demonstrated positive effects on angiogenesis in preclinical models and promising therapeutic efficacy signals in early stage clinical studies; however, the mechanisms underlying MSC-mediated angiogenesis remain largely undefined. Here, we investigated the mechanism of action of human placenta-derived MSC-like cells (PDA-002) in inducing angiogenesis using mice hind limb ischemia model. We showed that PDA-002 improved blood flow and promoted collateral vessel formation in the injured limb. Histological analysis demonstrated that PDA-002 increased M2-like macrophages in ischemic tissue. Analysis of the changes in functional T cell phenotype in the draining lymph nodes revealed that PDA-002 treatment was associated with the induction of cytokine and gene expression signatures of Th2 response. Angiogenic effect of PDA-002 was markedly reduced in Balb/c nude mice compared with wild type. This reduction in efficacy was reversed by T cell reconstitution, suggesting T cells are essential for PDA-002-mediated angiogenesis. Furthermore, effect of PDA-002 on macrophage differentiation was also T cell-dependent as a PDA-002-mediated M2-like macrophage skewing was only observed in wild type and T cell reconstituted nude mice, but not in nude mice. Finally, we showed that PDA-002-treated animals had enhanced angiogenic recovery in response to the second injury when PDA-002 no longer persisted in vivo. These results suggest that PDA-002 enhances angiogenesis through an immunomodulatory mechanism involving T cell-dependent reprogramming of macrophage differentiation toward M2-like phenotype. Stem Cells 2017;35:1603-1613.

The diffusion-dependent kinetic properties of the yeast glyoxalase I reaction have been measured by means of viscosometric methods. For the glyoxalase-I-catalyzed isomerization of glutathione (GSH)-methylglyoxal thiohemiacetal to S-D-Iactoylghtathione, the k,,,lK, (3.5 X 10" M-' s-', pH 7, 25 "C) undergoes a progressive decrease in magnitude with increasing solution viscosity, using sucrose as a viscogenic agent. The viscosity effect is unlikely to be due to a sucrose-induced change in the intrinsic kinetic properties of the enzyme, as the magnitude of k,.,,lK,, for the slow substrate GSH-t-butylglyoxal thiohemiacetal (3.5X1O3M-' s-', pH 7, 25OC) is independent of solution viscosity. Quantitative treatment of the data by means of the Stokes-Einstein diffusion law suggests that catalysis will be about 50% diffusion limited under conditions where [substrate] < K,; the encounter complex between enzyme and substrate partitions nearly equally between product formation and dissociation to form free enzyme and substrate. In a related study, the steady-state concentrations of glyoxalase-pathway intermediates in glycolyzing human erythrocytes are estimated to be in the nanomolar concentration range, on the basis of published values for the activities of glyoxalase I and glyoxalase I1 in lysed erythrocytes and the steady-state rate of formation of D-lactate in intact erythrocytes. This is consistent with a model of the glyoxalase pathway in which the enzyme-catalyzed steps are significantly diffusion limited under physiological conditions.