New part of the immune system identified, expected to evolve vaccination.

When a person is exposed to an infection, they are often protected from getting the same infection again by immune memory, the part of the immune system capable of remembering infectious agents.  However, it is still unclear just how the immune system can fight back so quickly when it encounters an infection it has been previously exposed to through a vaccine or an earlier infection.  Now, a study from researchers at the Garvan Institute of Medical Research identifies the existence of a previously unknown micro-organ within the immune system they have named the Subcapsular Proliferative Foci (SPF).  The team states the thin, flattened structures, extending over the surface of lymph nodes, are dynamic structures, only appearing on command to fight an infection the animal has previously been exposed to.  The opensource study is published in the journal Nature Communications.

Previous studies suggest memory B cells are formed within the lymph nodes and spleen following a primary infection and are known to generate an accelerated and more robust antibody-based immune response in the case of re-infection.  However, exactly where and how memory B cells are reactivated to make neutralizing antibodies remains unknown.  The current study identifies memory B cells in a subcapsular niche in lymph nodes where, upon reactivation by antigen, they rapidly proliferate and differentiate into antibody-secreting plasma cells in the newly discovered SPF.

The current study uses two-photon microscopy and single-cell RNA sequencing to identify the primary source of the secondary antibody response to identify the seat of B cell memory in a previously unknown structure termed the SPF. Results show memory B cells were clustered at the SPF and were changing into infection-fighting plasma cells, a key step in the fight against infection where plasma cells make antibodies to recognize and fend off foreign bodies and protect against disease.

The lab explains up until now the global medical community has been focussed on making vaccines generating memory B cells.  They go on to add the discovery of this new structure suggests the focus needs to be on understanding how those memory B cells are reactivated to make plasma cells so the process can be streamlined.

The team surmises they have identified a new part of the immune system, the SPF, where the immune system remembers past infections and vaccinations to mount a rapid response against an infection the body has seen before.  For the future, the researchers state their new discovery is an important step towards understanding how to make better vaccines.

Source: Garvan Institute of Medical Research

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