Project description:Follicular helper T (Tfh) cells are necessary for germinal center B cell maturation during primary immune responses; however, the T cells that promote humoral recall responses via memory B cells are less well defined. We herein characterize a human tonsillar CD4+ T cell subset with this function. These cells are similar to Tfh cells in terms of expression of the chemokine receptor CXCR5 and the inhibitory receptor PD-1, interleukin (IL)-21 secretion, and expression of the transcription factor BCL6; however, unlike Tfh cells that are located within the B cell follicle and germinal center, they reside at the border of the T cell zone and the B cell follicle in proximity to memory B cells, a position dictated by their unique chemokine receptor expression. They promote memory B cells to produce antibodies via CD40 ligand, IL-10, and IL-21. Our results reveal a unique extrafollicular CD4+ T cell subset in human tonsils, which specialize in promoting T cell-dependent humoral recall responses.
Project description:Autoantibodies against nucleic acids are a hallmark of Systemic Lupus Erythematosus. We recently uncovered that human oxidized DNA of mitochondrial origin released by activated lupus neutrophils represents a distinct class of interferogenic TLR9 ligand for plasmacytoid dendritic cells. We now show that oxidized mitochondrial DNA-activated plasmacytoid dendritic cells skew naïve CD4+ T cells towards IL2low, IFNγhigh, IL10high secreting B helper cells different from follicular helper and Type 1 regulatory CD4+ T cells. Furthermore, PD1-induced succinate and mitochondrial ROS accumulation revoke anergy, while IL10 and succinate synergize to deliver B cell help. We provide evidence that IL10-producing CD4+ T cells infiltrate the SLE kidney insterstitium, where they might play a role in extrafollicular B cell responses. Thus, we describe a novel B cell helper pathway that links innate and adaptive immunity alterations in human lupus.
Project description:<p>We use next generation sequencing to investigate the different transcriptomes of closely related CD4+ T-cells from healthy human donors to elucidate the genetic programs that underlie their specialized immune functions. Six cell types were included: Regulatory T-cells (CD25hiCD127low/neg with >95% FOXP3+ purity), regulatory T-cells activated using PMA/ionomycin, CD25-CD45RA+ ('naive' helper T-cells), CD25-CD45RO+ ('memory' helper T-cells), activated Th17 cells (>98% IL17A+ purity) and activated IL17-CD4+ T-cells (called 'ThPI'). Poly-T capture beads were used to isolate mRNA from total RNA, and fragment sizes of ~200 were sequenced from both ends on Illumina's genome analyzer. We confirm many of the canonical signature genes of T-cell populations, but also discover new genes whose expression is limited to specific CD4 T-cell lineages, including long non-coding RNAs. Additionally, we find that genes encoded at loci linked to multiple human autoimmune diseases are enriched for preferential expression upon T-cell activation, suggesting that an aberrant response to T-cell activation is fundamental to pathogenesis.</p>
Project description:The vast majority of currently licensed human vaccines work on the basis of long-term protective antibody responses. Generation of long term humoral immunity is a complex process predominantly dependent on germinal centers and CD4 T cell help to B cells. Follicular helper T cells (Tfh) are the specialized CD4 T cells for B cell help. However, whether such cells develop memory in humans and can be tracked in human blood has been enigmatic. We identified a subpopulation of blood CXCR5+ PD-1+CXCR3- resting CD4 T cells that are most related to Tfh cells of lymphoid tissue by gene expression profile and phenotype. Functional analysis showed that these memory Tfh cells were specialized for helping B cells. Moreover, these cells correlate with a clinically important outcome: development of potent neutralizing antibodies against HIV in HIV+ individuals. CD4 T cells were enriched from fresh blood of 5 normal donors by magnetic beads negative selection. Following enrichment, CD14-CD16-CD19-CD8-CD4+CD45RA- cells from each donor were FACS sorted into the following 5 populations: CXCR5-, CXCR5+PD1+CXCR3-, CXCR5+PD1+CXCR3+, CXCR5+PD1-CXCR3-, and CXCR5+PD1-CXCR3+. The gene expression profile of each cell population was determined.
Project description:A better understanding of the mechanisms involved in human plasma cell differentiation will accelerate therapeutic target identification in autoantibody-mediated diseases such as Systemic Lupus Erythematosus (SLE). Here, we describe a novel CXCR5- CXCR3+ PD1hi CD4+ T cell ‘helper’ population distinct from follicular helper T cells (Tfh) and expanded in blood and inflamed kidneys of SLE patients. Upon activation, these cells express IFNand high levels of IL10. Additionally, they accumulate high amounts of mitochondrial ROS (mtROS) as the result of reverse electron transport (RET) fueled by succinate. These cells provide potent help to B cells through the synergistic effect of IL10 and succinate. Cells with similar phenotype and function are generated in vitro upon priming naïve CD4+ T cells with oxidized mitochondrial DNA (Ox mtDNA)-activated plasmacytoid dendritic cells (pDCs) in a PD1-dependent manner. Our results provide a novel mechanism for the initiation and/or perpetuation of extrafollicular humoral responses in SLE.