Tolerogenic insulin peptide therapy precipitates type 1 diabetes.

Daniel et al. (https://doi.org/10.

Old dogs and new tricks: defective peripheral regulatory T cell generation in aged mice.

Tolerance is a developmentally acquired property of the vertebrate immune system, in part ensured by regulatory CD4⁺ lymphocytes (Treg cells) expressing the Foxp3 transcription factor. Recent work has shown that thymic emigrants are the preferential source of peripherally generated Treg cells. A new report in this issue of the European Journal of Immunology [Eur.

Marginal zone B cells in lymphocyte activation and regulation.

Marginal zone (MZ) B cells, together with other strategically located innate cells, constitute the first line of defense against blood-borne microorganisms, viruses and toxins in the spleen. Their fast and efficient protective antibody responses are well characterized; however, much less is known of their interactions with other cell types during immune responses. Recent work has demonstrated that MZ B cells can directly activate T cells; and MZ B cells also interact with other antigen presenting cells, transporting and concentrating antigen during the course of T-dependent and T-independent immune responses.

Foxp3+ CD25- CD4 T cells constitute a reservoir of committed regulatory cells that regain CD25 expression upon homeostatic expansion.

Expression of the IL-2 receptor alpha chain (CD25) by peripheral CD4 T cells follows cellular activation. However, CD25 expression by CD4 cells is widely used as a marker to identify regulatory T cells (T(R)), although cells with regulatory properties are also found in the CD4+CD25- subset. By using in vivo functional assays and Foxp3 expression as a faithful marker of T(R) differentiation, we have evaluated the requirements for CD25 expression by peripheral T(R).

Marginal zone B cell physiology and disease.

Mature B lymphocytes do not constitute a homogenous pool of cells, and it is now clear that several functionally and developmentally distinct subsets exist. Of these, marginal zone (MZ) B cells are a subset of peripheral B cells that respond vigorously to blood-borne infections, and play a vital role, particularly in host survival of infection by encapsulated bacteria. Their fast activation and differentiation to antibody-secreting plasma cells allows MZ B cells to bridge the gap between innate and adaptive immunity, effected mainly by the more prolific follicular B cells.

Development and selection of marginal zone B cells.

It is now clear that functionally distinct subsets of mature peripheral B cells exist. Of these subsets, marginal zone (MZ) B cells in the spleen are strategically positioned at the blood-lymphoid interface and are programmed to initiate a fast and intense antibody response to blood-borne viral and bacterial agents. Their ability to respond vigorously to antigen and polyclonal activators make MZ B cells key players in the early response to pathogens in the bloodstream.

Regulatory T cells selectively express toll-like receptors and are activated by lipopolysaccharide.

Regulatory CD4 T cells (Treg) control inflammatory reactions to commensal bacteria and opportunist pathogens. Activation of Treg functions during these processes might be mediated by host-derived proinflammatory molecules or directly by bacterial products. We tested the hypothesis that engagement of germline-encoded receptors expressed by Treg participate in the triggering of their function.