Newly discovered mechanism controls the number of immune cells

"The findings in the present dissertation have uncovered new mechanisms that regulate cells of the immune system, more precisely the B lymphocytes. Such knowledge may be important in development of future strategies to either improve or dampen the amount of immune cells in the body," says Shrikant Shantilal Kolan, postgraduate student at the Department of Integrative Medical Biology at Umeå University.

B lymphocytes are one type of white blood cells that is fundamental for the immune system to defend off attacking bacteria or viruses. B lymphocyte development from stem cells begins in the bone marrow and ends with the generation of mature B lymphocytes in the spleen or in the bone marrow itself. In the human body, B lymphocytes are maintained in large numbers -- around 100 billion. However, defects in the development of B lymphocytes, or in their function, may lead to blood cancers or immune-deficiencies.

Shrikant Shantilal Kolan has in his dissertation investigated new mechanisms involved in regulating B lymphocyte development and maturation. The dissertation shows that two cell surface proteins, CD47 and SIRPα, are each important to develop normal numbers of B lymphocytes. Although the exact details remain to be understood, these two proteins may be important to prevent death of developing B lymphocytes and to promote the long-term survival of the vast majority of all B lymphocytes.

The proteins CD47 and SIRPα were also found to have the opposite effect on a smaller subset of B lymphocytes, the so called marginal zone (MZ) B lymphocytes of the spleen. For this B lymphocyte subset, CD47 and SIRPα were found to be required to prevent an abnormal accumulation of these cells with an increasing age.

"The effects of CD47 and SIRPα in regulating B lymphocyte development was found to be complex and require further studies. The presence and function of the proteins in either immune cells or non-immune cells was found to affect this process differently," says Shrikant Shantilal Kolan.

The dissertation is available online at: http://umu.diva-portal.org/smash/record.jsf?pid=diva2%3A848526&dswid=4640