Initiation of an immune response requires interactions between cells of the immune system. Fragments of proteins (called antigens), from viruses or bacteria that have entered the body, bind to proteins on the surface of antigen-presenting cells, which then interact with T-cells. This interaction enables T-cells to recognize the antigen, and induces T-cell activation, so that an attack on the invader can be mounted.
Interactions between immune system cells in culture are mediated by structures called immunological synapses. Many researchers believed that these structures were artifacts produced by experimental conditions, and doubted that they existed in live animals.
Now, researchers at Cedars-Sinai Medical Center, confirm the existence of immunological synapses in vivo; they report their findings in the Journal of Experimental Medicine.
Pedro Lowenstein and his colleagues found evidence for the immunological synapses while investigating how the immune system clears astrocytes infected with adenoviruses from the mouse brain.
Synapses between immune system cells are characterized by the formation supramolecular activation clusters (SMACs). These clusters form between receptors on the surface of T-cells and major histocompatability complex (MHC) proteins, on the surface of antigen-presenting cells, to which fragments of viral or bacterial proteins are bound. SMAC formation involves a rearragement of the actin cytoskeleton and the activation of signalling pathways which result in changes in gene expression.
Lowenstein’s team used antibody staining on brain tissue from mice to confirm that SMACs formed during the brain’s immune response to the adenovirus.
I think that neuro-immunological synapses may also exist. As their name suggests, these would mediate communication between the nervous and immune systems.