B cells baffle T cells

Sydney researchers investigating the role of the cytokine known as BAFF have found that while it has a normal pro-inflammatory function, it also has a surprising role in regulating T cell response, in an anti-inflammatory manner.

BAFF (B cell activation of the TNF family) is considered to be primarily involved in B cell activation, as its name suggests, but previous studies have shown that it may also be involved in the regulation of T cell response.

In vitro studies have shown that higher levels of BAFF co-stimulates both human and mouse T cells, and in vivo studies have shown that BAFF-transgenic mice display exaggerated T-dependent antigen responses.

It has also been observed that loss of BAFF signalling impairs the development of antigen-specific T cell responses.

All of this data shows that BAFF has a pro-inflammatory role with regard to T cells.

Now, however, researchers led by PhD student Stacey Walters and Dr Shane Grey of the Garvan Institute in Sydney have found that when BAFF is over-expressed, it has also has an anti-inflammatory role, with effector T cells unable to do their duty.

In fact, in BAFF transgenic mice, T cell effector responses were profoundly compromised, to the extent of accepting tissue allografts.

The reason behind this is that increased levels of BAFF expands the number of CD4+ Foxp3+ regulatory T cells, which are known to inhibit immune responses. It was not thought previously that B cells had a role in T regulatory cells, but this study, the researchers say, shows that BAFF has a complex, dichotomous role to play in immunity.

The work is published in the Journal of Immunology.