Leptin acts in the periphery to protect thymocytes from glucocorticoid-mediated apoptosis in the absence of weight loss.

Leptin is a member of the IL-6 cytokine family and is primarily produced by adipose tissue. At high enough concentration, leptin engages leptin receptors expressed in the hypothalamus that regulate a variety of functions, including induction of weight loss. Mice deficient in leptin (ob/ob) or leptin receptor (db/db) function exhibit thymic atrophy associated with a reduction in double-positive (DP) thymocytes. However, the mediator of such thymic atrophy remains to be identified, and the extent to which leptin acts in the periphery vs. the hypothalamus to promote thymocyte cellularity is unknown. In the present study, we first demonstrate that thymic cellularity and composition is fully restored in ob/ob mice subjected to adrenalectomy. Second, we observe that ob/ob mice treated with low-dose leptin peripherally but not centrally exhibit increased thymocyte cellularity in the absence of any weight loss or significant reduction in systemic corticosterone levels. Third, we demonstrate that reconstitution of db/db mice with wild-type bone marrow augments thymocyte cellularity and restores DP cell frequency despite elevated corticosterone levels. These and additional data support a mode of action whereby leptin acts in the periphery to reduce the sensitivity of DP thymocytes to glucocorticoid-mediated apoptosis in vivo. Strikingly, our data reveal that leptin's actions on thymic cellularity in the periphery can be uncoupled from its anorectic actions in the hypothalamus.

Axicabtagene ciloleucel, a first-in-class CAR T cell therapy for aggressive NHL.

The development of clinically functional chimeric antigen receptor (CAR) T cell therapy is the culmination of multiple advances over the last three decades. Axicabtagene ciloleucel (formerly KTE-C19) is an anti-CD19 CAR T cell therapy in development for patients with refractory diffuse large B cell lymphoma (DLBCL), including transformed follicular lymphoma (TFL) and primary mediastinal B cell lymphoma (PMBCL). Axicabtagene ciloleucel is manufactured from patients' own peripheral blood mononuclear cells (PBMC) during which T cells are engineered to express a CAR that redirects them to recognize CD19-expressing cells. Clinical trials have demonstrated the feasibility of manufacturing axicabtagene ciloleucel in a centralized facility for use in multicenter clinical trials and have demonstrated potent antitumor activity in patients with refractory DLBCL. Main acute toxicities are cytokine release syndrome and neurologic events. Axicabtagene ciloleucel holds promise for the treatment of patients with CD19-positive malignancies, including refractory DLBCL.

Differential ex vivo nitric oxide production by acutely isolated neonatal and adult microglia.

Microglia are the macrophage population residing in the parenchyma of the central nervous system (CNS), and are thought to play critical roles in CNS development, homeostasis and defense against pathogens. Microglia are capable of rapidly responding to microbial pathogens through engagement of their Toll-like receptors (TLRs). We first compared the efficiency of these responses in primary microglia acutely isolated from adult and neonatal mice. While the cytokine and chemokine responses of adult microglia were generally higher than those of neonatal cells stimulated ex vivo through TLRs, the nitric oxide response of neonatal microglia was markedly enhanced relative to the adult cells. We then went on to identify culture conditions such as exposure to M-SCF or GM-CSF that markedly enhanced the nitric oxide response of microglia, particularly those from the adult CNS. Finally, we demonstrate that the differential nitric oxide response of neonatal and adult microglia is not only limited to the mouse, but also extends to rat microglia.

Transneuronal mapping of the CNS network controlling sympathetic outflow to the rat thymus.

The thymus is a primary immune organ that is essential for the development of functional T cells. The thymus receives sympathetic innervation, and thymocytes and thymic epithelial cells express functional adrenergic receptors. In this study, we employed retrograde, transneuronal virus tracing to identify the CNS cell groups that regulate sympathetic outflow to the thymus. Pseudorabies virus (PRV) was injected into the thymus, and the pattern of PRV infection in sympathetic regulatory centers of the CNS was determined at 72 and 120 h post-inoculation. PRV infection within the CNS first appeared within the spinal cord at 72 h post-inoculation and was confined to neurons within the intermediolateral cell column at levels T1-T7. At 120 h post-inoculation infection had spread within the spinal cord to include the central autonomic nucleus, intercalated cell nucleus and light infection within the cells of the lateral funiculus. Within the brain, PRV positive cells were found within nuclei of the medulla oblongata, pons and hypothalamus. Infection in the hypothalamus was observed within the arcuate nucleus, dorsal, lateral, and posterior hypothalamus and in all parvicellular subdivisions of the paraventricular hypothalamic nucleus. None of the infected animals exhibited labeling of the dorsal motor nucleus of the vagus. In summary, this study provides the first anatomic map of CNS neurons involved in control of sympathetic outflow to the thymus.

Differential contribution of beta-adrenergic receptors expressed on radiosensitive versus radioresistant cells to protection against inflammation and mortality in murine endotoxemia.

The sympathetic nervous system modulates immune responses via the secretion of catecholamines and subsequent activation of adrenergic receptors (ARs), and systemic catecholamine levels increase markedly in the setting of endotoxemia and sepsis. Previous studies have demonstrated that stimulation of beta-ARs by pharmacological agonists attenuates the inflammatory response to LPS observed in vitro and can increase survival in animal models of endotoxemia and sepsis. However, the consequences of beta-AR activation by endogenous catecholamines have not been explored in these settings. Furthermore, the relative contribution of beta-ARs expressed on immune versus nonimmune cells to LPS-mediated inflammation and mortality is not known. Our first goal was therefore to determine the impact of beta-AR stimulation by endogenous catecholamines released during endotoxemia on LPS-mediated inflammation and mortality in vivo. To address this question, we examined the LPS response of mice lacking all three known betaAR subtypes, beta1-, beta2-, and beta3-AR, and demonstrated that these beta-less mice exhibited a net increase in inflammation (increased TNF-alpha levels and decreased IL-10 levels in serum) and a 50% decrease in survival relative to wild-type animals. The second goal of our study was to determine the relative contribution of beta-ARs expressed on radiosensitive immune versus radioresistant cells to the protective action of beta-ARs in the setting of endotoxemia. We therefore examined the LPS response of bone marrow chimeras generated between beta-less and wild-type mice, and concluded that beta-ARs expressed on radioresistant cells play the dominant role in protecting against LPS-mediated mortality and attenuating systemic TNF-alpha responses. Finally, we determined that beta3-AR subtype does not play a significant role in regulating LPS-mediated mortality and inflammation by evaluating mice lacking the beta1- and beta2-AR subtypes only.

Resident microglia from adult mice are refractory to nitric oxide-inducing stimuli due to impaired NOS2 gene expression.

Microglia are the immunoregulatory cells of the central nervous system (CNS) and share many characteristics with resident macrophages in extracerebral tissues. Nitric oxide (NO) is secreted by macrophages following induction of the NO synthase gene NOS2 by stimuli elicited during a T-cell response and/or by microbial products. NO regulates both innate and adaptive immune responses, such as killing intracellular pathogens and inhibiting T-cell proliferation. Regulation of NO production by microglia, however, is poorly understood. We find that microglia from healthy adult mice produce negligible amounts of NO compared with resident macrophages during restimulation of peptide-specific CD8 T cells, and therefore cannot block T-cell proliferation. The impaired NO response extends to exogenous NOS2-inducing stimuli, including cytokines, CD40 ligation, and lipopolysaccharide. In contrast, microglia produce proinflammatory cytokines in response to these same stimuli, and therefore possess a relatively selective block in NO production. We go on to show that resident microglia fail to produce detectable levels of either the NOS2 enzyme or NOS2 RNA in response to NO-inducing stimuli. We therefore propose that microglia in the healthy adult brain exist in an "NO-incompetent" state in which NO production is blocked at the level of NOS2 RNA. The inability of resident microglia in the healthy CNS to produce NO may allow these immunoregulatory cells to modulate immune processes temporally, and may serve to protect the CNS from irreparable damage at the onset of infection or injury.

Developmental dissociation of T cells from B, NK, and myeloid cells revealed by MHC class II-specific chimeric immune receptors bearing TCR-zeta or FcR-gamma chain signaling domains.

The T-cell receptor zeta (TCR-zeta) and FcR-gamma chains play a critical role in mediating signal transduction. We have previously described HIV glycoprotein 120 (gp120)-specific chimeric immune receptors (CIRs) in which the extracellular domain of CD4 is linked to the signaling domain of zeta (CD4zeta) or gamma (CD4gamma). Such CIRs are efficiently expressed following retroviral transduction of mature T cells and specifically redirect effector functions toward HIV-infected targets. In this report, we examine development of CD4zeta- or CD4gamma-expressing T cells from retrovirally transduced hematopoietic stem cells following bone marrow transplantation. Although CD4zeta/gamma-expressing myeloid, NK, and B cells were efficiently reconstituted, parallel development of CD4zeta/gamma-expressing T cells was blocked prior to the CD25(+)CD44(+) prothymocyte stage. In contrast, T cells expressing a signaling-defective CIR were efficiently generated. When major histocompatibility complex (MHC) class II-deficient mice were used as transplant recipients, development of CD4zeta/gamma-expressing T cells was restored. We conclude that CD4zeta/gamma signaling generated following engagement of MHC class II selectively arrests T-lineage development.