Generation and Regulation of CD8+ Regulatory T Cells

Research into the suppressive activity of CD4+FoxP3+ T regulatory cells (Treg) has defined a sublineage of CD4+ cells that contribute to self-tolerance and resistance to autoimmune disease. Much less attention has been given to the potential contribution of regulatory sublineages of CD8+ cells. Analysis of a small fraction of CD8+ cells that target autoreactive CD4+ cells through recognition of the MHC class Ib molecule Qa-1 in mouse and HLA-E in human has revitalized interest in CD8+ Treg. Here we summarize recent progress and future directions of research into the role of this CD8+ sublineage in resistance to autoimmune disease

Preliminary Studies on the Use of Monoclonal Antibodies as Probes for Sympathetic Development

The precise structural organization and proper functioning of the adult nervous system depend on the ability of neurones to make highly ordered synaptic connexions. To define molecules involved in the development of these connexions and to study their functional roles, we use primary cultures of dissociated rat sympathetic neurones grown in the virtual absence of non-neuronal cells. These neurones can develop adrenergic or cholinergic properties, depending on the environment in which they are grown. This ability to manipulate neuronal phenotype is being used in an attempt to identify cell surface macromolecules that are important in the development or function of adrenergic and cholinergic properties. We have produced monoclonal antibodies against the surface membranes of these neurones and are in the process of characterizing them. Results are presented on the binding specificity of one of these antibodies and on the effect of two other antibodies on neurotransmitter synthesis, uptake, and release

Negative selection, not receptor editing, is a physiological response of autoreactive thymocytes

Antigen receptor editing—a process of secondary rearrangements of antigen receptor genes in autoreactive lymphocytes—is a well-established tolerance mechanism in B cells, whereas its role in T cells remains controversial. Here, we investigated this issue using a novel Tcra knock-in locus, which ensured appropriate timing of TCRα expression and allowed secondary rearrangements. Under these conditions the only response to self-antigen that could be unambiguously identified was negative selection of CD4/CD8 double positive thymocytes. No evidence could be obtained for antigen-induced TCR editing, whereas replacement of the transgenic TCRα chain by ongoing gene rearrangement occurred in some cells irrespective of the presence or absence of self-antigen

The effect of osteopontin and osteopontin-derived peptides on preterm brain injury

Background: Osteopontin (OPN) is a highly phosphorylated sialoprotein and a soluble cytokine that is widely expressed in a variety of tissues, including the brain. OPN and OPN-derived peptides have been suggested to have potential neuroprotective effects against ischemic brain injury, but their role in preterm brain injury is unknown. Methods: We used a hypoxia-ischemia (HI)-induced preterm brain injury model in postnatal day 5 mice. OPN and OPN-derived peptides were given intracerebroventricularly and intranasally before HI. Brain injury was evaluated at 7 days after the insults. Results: There was a significant increase in endogenous OPN mRNA and OPN protein in the mouse brain after the induction of HI at postnatal day 5. Administration of full-length OPN protein and thrombin-cleaved OPN did not affect preterm brain injury. This was demonstrated with both intracerebroventricular and intranasal administration of OPN as well as in OPN-deficient mice. Interestingly, both N134–153 and C154–198 OPN-derived peptides increased the severity of brain injury in this HI-induced preterm brain injury model. Conclusions: The neuroprotective effects of OPN are age-dependent, and, in contrast to the more mature brain, OPN-derived peptides potentiate injury in postnatal day 5 mice. Intranasal administration is an efficient way of delivering drugs to the central nervous system (CNS) in neonatal mice and is likely to be an easy and noninvasive method of drug delivery to the CNS in preterm infants

SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : III. EVIDENCE FOR INTERACTION BETWEEN TWO TYPES OF THYMUS-DERIVED CELLS

Two types of thymus-derived (T) lymphocytes have been shown to cooperate in the induction of graft-versus-host responses. One cell type is found in highest concentrations in the peripheral blood and lymph node, is extremely sensitive to anti-thymocyte serum (ATS) in vivo, and is probably part of the recirculating lymphoid cell pool (3). The second cell type, found in highest concentrations in the thymus and spleen, is relatively resistant to small doses of ATS in vivo. Both cell types are substantially depleted after neonatal thymectomy. Moreover, since synergism was also obtained using appropriate mixtures of cells from either parental strain in F1 hosts, it was possible to show that the nonrecirculating cells determined the specificity of the response and were probably the precursors of effector cells in this response. The recirculating T cell appeared to amplify this response. The implications of these data are discussed

SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : II. SYNERGY IN GRAFT-VERSUS-HOST REACTIONS PRODUCED BY BALB/C LYMPHOID CELLS OF DIFFERING ANATOMIC ORIGIN

The capacity of cells from different lymphoid tissues obtained from Balb/c mice to produce graft-vs.-host (GVH) reactions was quantitatively determined in C57BL/6N by Balb/c F1 hybrid recipients. Synergistic responses were observed when small numbers of cells from lymphoid tissues that were rich in GVH activity such as spleen and femoral lymph node were combined with weakly reactive thymus cells. Thymus and spleen cells obtained from 1-wk old mice were separately inactive but produced moderate GVH reactions when combined in equal proportions. GVH activity of spleen cells from mice thymectomized at 3 days of age was partially restored by the addition of small numbers of spleen or thymus cells from adult mice. Changes in ratio between the two cell populations markedly affected the degree of synergy. Synergy was not observed when Balb/c cells were combined with Balb/c x C57BL/6N F1 hybrid cells and inoculated into C57BL/6N recipients, but was demonstrated when Balb/c and C57BL/6N cells were combined and inoculated into F1 recipients, indicating that a genetic disposition to mount GVH reactions in both populations is required to produce synergy. The data indicate that at least two cell types are necessary for GVH reactions, and that synergy between cell populations results from favorable adjustments in the ratio between these two cell types

The immune response after hypoxia-ischemia in a mouse model of preterm brain injury

Background: Preterm brain injury consists primarily of periventricular leukomalacia accompanied by elements of gray-matter injury, and these injuries are associated with cerebral palsy and cognitive impairments. Inflammation is believed to be an important contributing factor to these injuries. The aim of this study was to examine the immune response in a postnatal day (PND) 5 mouse model of preterm brain injury induced by hypoxia-ischemia (HI) that is characterized by focal white and gray-matter injury. Methods: C57Bl/6 mice at PND 5 were subjected to unilateral HI induced by left carotid artery ligation and subsequent exposure to 10% O2 for 50 minutes, 70 minutes, or 80 minutes. At seven days post-HI, the white/gray-matter injury was examined. The immune responses in the brain after HI were examined at different time points after HI using RT-PCR and immunohistochemical staining. Results: HI for 70 minutes in PND 5 mice induced local white-matter injury with focal cortical injury and hippocampal atrophy, features that are similar to those seen in preterm brain injury in human infants. HI for 50 minutes resulted in a small percentage of animals being injured, and HI for 80 minutes produced extensive infarction in multiple brain areas. Various immune responses, including changes in transcription factors and cytokines that are associated with a T-helper (Th)1/Th17-type response, an increased number of CD4+ T-cells, and elevated levels of triggering receptor expressed on myeloid cells 2 (TREM-2) and its adaptor protein DNAX activation protein of 12 kDa (DAP12) were observed using the HI 70 minute preterm brain injury model. Conclusions: We have established a reproducible model of HI in PND 5 mice that produces consistent local white/gray-matter brain damage that is relevant to preterm brain injury in human infants. This model provides a useful tool for studying preterm brain injury. Both innate and adaptive immune responses are observed after HI, and these show a strong pro-inflammatory Th1/Th17-type bias. Such findings provide a critical foundation for future studies on the mechanism of preterm brain injury and suggest that blocking the Th1/Th17-type immune response might provide neuroprotection after preterm brain injury

SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : I. SYNERGY IN GRAFT-VERSUS-HOST REACTIONS PRODUCED BY CELLS FROM NZB/BL MICE

The ability of spleen cells from young (3 month) and old (1 yr) NZB mice to induce GVH reactions in newborn C57BL/6N mice was compared quantitatively using the Simonsen spleen assay. Young NZB cells were five times more reactive than cells from older mice. The minimum number of cells producing detectable reactions was 2 x 106 for the young and 10 x 106 for the old. Young and old cells combined and injected together produced GVH reactions quantitatively similar to those obtained with inocula composed of young cells alone. Mixtures of two cell populations producing no detectable reactions when injected separately into different recipients (1 x 106 young cells and 4 x 106 old cells) produced reactions approximately equal to those obtained with 5 x 106 young cells. As few as 0.25 x 106 young cells were sufficient to effect a reaction when combined with 4.75 x 106 old unreactive cells. Viability of both cell populations was essential for GVH reactivity. This evidence of synergy in GVH reactions indicates that old NZB spleen cells can be rendered immunologically more reactive in the presence of a normally reactive population

The mTORC1/4E-BP pathway coordinates hemoglobin production with L-leucine availability

In multicellular organisms, the mechanisms by which diverse cell types acquire distinct amino acids and how cellular function adapts to their availability are fundamental questions in biology. We found that increased neutral essential amino acid (NEAA) uptake was a critical component of erythropoiesis. As red blood cells matured, expression of the amino acid transporter gene Lat3 increased, which increased NEAA import. Inadequate NEAA uptake by pharmacologic inhibition or RNAi-mediated knockdown of LAT3 triggered a specific reduction in hemoglobin production in zebrafish embryos and murine erythroid cells through the mTORC1 (mammalian target of rapamycin complex 1)/4E-BP (eukaryotic translation initiation factor 4E–binding protein) pathway. CRISPR-mediated deletion of members of the 4E-BP family in murine erythroid cells rendered them resistant to mTORC1 and LAT3 inhibition and restored hemoglobin production. These results identify a developmental role for LAT3 in red blood cells and demonstrate that mTORC1 serves as a homeostatic sensor that couples hemoglobin production at the translational level to sufficient uptake of NEAAs, particularly L-leucine.National Institutes of Health (U.S.) (P01 HL032262