Feedback regulation of autoimmunity via TCR-centered regulation

Genetically modified hematopoietic stem/progenitor cells that produce IL-10-secreting regulatory T cells

Random amino acid copolymers used in the treatment of multiple sclerosis in man or experimental autoimmune encephalomyelitis (EAE) in mice [poly(Y,E,A,K)_n, known as Copaxone, and poly(Y,F,A,K)_n] function at least in part by generation of IL-10-secreting regulatory T cells that mediate bystander immunosuppression. The mechanism through which these copolymers induce Tregs is unknown. To investigate this question, four previously described Vα3.2 Vβ14 T cell receptor (TCR) cDNAs, the dominant clonotype generated in splenocytes after immunization of SJL mice, that differed only in their CDR3 sequences were utilized to generate retrogenic mice. The high-level production of IL-10 as well as IL-5 and small amounts of the related cytokines IL-4 and IL-13 by CD4⁺ T cells isolated from the splenocytes of these mice strongly suggests that the TCR itself encodes information for specific cytokine secretion. The proliferation and production of IL-10 by these Tregs was costimulated by activation of glucocorticoid-induced TNF receptor (GITR) (expressed at high levels by these cells) through its ligand GITRL. A mechanism for generation of cells with this specificity is proposed. Moreover, retrogenic mice expressing these Tregs were protected from induction of EAE by the appropriate autoantigen.

Sercarzian immunology--In memoriam. Eli E. Sercarz, 1934-2009

During his long career as a principal investigator and educator, Eli Sercarz trained over 100 scientists. He is best known for developing hen egg white lysozyme (HEL) as a model antigen for immunologic studies. Working in his model system Eli furthered our understanding of antigen processing and immunologic tolerance. His work established important concepts of how the immune system recognizes antigenic determinants processed from whole protein antigens; specifically he developed the concepts of immunodominance and crypticity. Later in his career he focused more on autoimmunity using a variety of established animal models to develop theories on how T cells can circumvent tolerance induction and how an autoreactive immune response can evolve over time. His theory of "determinant spreading" is one of the cornerstones of our modern understanding of autoimmunity. This review covers Eli's entire scientific career outlining his many seminal discoveries.

Armed response: how dying cells influence T-cell functions

Immune responses during infection, injury, and cancer proceed in the presence of tissue injury and cell death. Consequently, the system must deal with its own dead cells while it determines the appropriate response to the invader. As apoptotic cells are known to induce immune tolerance and necrotic cells can be potent stimulators of immunity, this decision becomes more complex. The key to understanding the immunologic choices made during cell death is to examine the mechanisms of tolerance induction by dying cells and then relate them to the mechanisms of immunity. Ideally, immunogenic cell death should be directed toward tumor cells and infected cells, whereas tolerogenic cell death should be associated with preventing unwanted immune responses to self. In this review, we discuss how the decision is made by focusing on the biochemical process of cell death and how its key components can influence both tolerance and immunity.

IL-10 mediates resistance to adoptive transfer experimental autoimmune encephalomyelitis in MyD88(-/-) mice

MyD88 is an adaptor molecule that functions in the innate signaling induced by proinflammatory adjuvants that interact with TLRs. Mice lacking MyD88, for example, resist active experimental autoimmune encephalomyelitis (EAE) induced by immunization with an encephalitogenic myelin oligodendrocyte glycoprotein (MOG) peptide in CFA. We reasoned that MyD88(-/-) mice, nevertheless, should be susceptible to EAE mediated by adoptive transfer of activated encephalitogenic T cell lines, which do not require adjuvant signaling for their effector functions. We now report, however, that mice lacking MyD88 also resist adoptive EAE mediated by an anti-MOG T cell line that is strongly encephalitogenic in wild-type (WT) mice. The transferred anti-MOG T cells proliferated, secreted INF-gamma, and migrated to the CNS in the MyD88(-/-) mice, as they did in WT mice, but inflammatory infiltrates did not progress and clinical EAE did not develop. The resistance of the MyD88(-/-) mice to adoptive EAE mediated by the otherwise encephalitogenic T cells was found to result from the secretion of IL-10 by recipient T cells of two different specificities: those specific for MOG and those responding to the T cell clone itself-both anticlonotypic and antiergotypic T regulators were detected. IL-10-producing anti-MOG T cells isolated from immunized MyD88(-/-) mice suppressed the induction of active EAE in WT recipients. Moreover, the absence of IL-10 production in MyD88/IL-10 double-knockout mice rendered the mice susceptible to adoptive transfer of EAE. Thus, MyD88 signaling appears to be a key factor in determining the cytokine phenotype of T cells involved in autoimmune inflammation and regulation.