Immunology

Background Increasing evidence points to a role for the extra-neuronal nerve growth factor (NGF) in acquired immune responses. However, very little information is available about its role and underlying mechanism in innate immunity.

Via Krishan Maggon

Abstract

The organization of the thymus into distinct cortical and medullary regions enables it to control the step-wise migration and development of immature T-cell precursors. Such a process provides access to specialized cortical and medullary thymic epithelial cells at defined stages of maturation, ensuring the generation of self-tolerant and MHC-restricted conventional CD4+ and CD8+ αβ T cells. The migratory cues and stromal cell requirements that regulate the development of conventional αβ T cells have been well studied. However, the thymus also fosters the generation of several immunoregulatory T-cell populations that form key components of both innate and adaptive immune responses. These include Foxp3+ natural regulatory T cells, invariant γδ T cells, and CD1d-restricted invariant natural killer T cells (iNKT cells). While less is known about the intrathymic requirements of these nonconventional T cells, recent studies have highlighted the importance of the thymus medulla in their development. Here, we review recent findings on the mechanisms controlling the intrathymic migration of distinct T-cell subsets, and relate this to knowledge of the microenvironmental requirements of these cells.

Via Krishan Maggon

Trogocytosis is a contact-dependent unidirectional transfer of membrane fragments between immune effector cells and their targets, initially detected in T cells following interaction with professional antigen presenting cells (APC).

Via Krishan Maggon

The Perverse and Often Baffling Immune Response to Prions

 

The holy grail of an effective vaccine is sterilizing immunity mediated by powerful neutralizing antibodies. Proof-of-principle has been shown in studies promoting mucosal immunity against prions [22]. The Complement system opsonizes most of the resulting antibody-antigen complexes, marking them for disposal mainly by Kupfer cells, the macrophages of the liver. However, compelling evidence shows that Complement facilitates prion transport to germinal centers within FDCs, where efficient prion replication occurs [9,23,24]. Generating prion-specific antibodies could therefore facilitate Complement trapping and transport of prions to draining lymph nodes—the very place they replicate most efficiently.

 

So maybe a cell-mediated response is better. Perhaps a more effective prion vaccine stimulates prion-specific T cells in the periphery to produce inflammatory cytokines like IFNγ, that can activate macrophages to phagocytose prions and degrade or at least sequester them, as has been shown to occur [6,7]. Such an atypical, cell-induced innate immune vaccine may be just what a host needs to respond to such an atypical pathogen. Or not, says Anne.

Via Krishan Maggon

Abstract

The immune system can remember a previously experienced pathogen and can evoke an enhanced response to reinfection that depends on memory lymphocyte populations. Recent advances in tracking antigen-experienced memory B cells have revealed the existence of distinct classes of cells that have considerable functional differences. Some of these differences seem to be determined by the stimulation history during memory cell formation. To induce rapid recall antibody responses, the contributions of other types of cells, such as memory T follicular helper cells, have also now begun to be appreciated. In this Review, we discuss these and other recent advances in our understanding of memory B cells, focusing on the underlying mechanisms that are required for rapid and effective recall antibody responses.

Via Krishan Maggon