Autologous haematopoietic stem cell transplantation (AHSCT) refers to an intensive chemotherapy treatment where a person’s immune system is completely or partially destroyed. Prior to undergoing chemotherapy, haematopoietic (blood and immune) stem cells are isolated from the person and then returned following the treatment to aid the regrowth of the immune system. For a more detailed description visit our webpages dedicated to AHSCT here.
This process of removal and rebooting of the immune system seems to benefit some patients with highly inflammatory MS that has not responded to other MS therapies. In many cases a prolonged remission can be achieved. The rebooted immune system seems to regrow in a manner which is more “self-tolerant” meaning it no longer attacks the person’s own body. However, how this works is not clear.
Dr Jennifer Massey, an MS Research Australia-supported researcher and her colleagues at the St Vincent Hospital in Sydney have just released a scientific manuscript collating and summarising what is currently known about how the immune system regenerates after AHSCT.
Collating and summarising previous knowledge is an important step in the scientific process. Discoveries and advancements don’t happen in a vacuum – they are built on previous knowledge, which avoids continuously ‘reinventing the wheel’.
Work in this area is needed to show us how the treatment works at the immune system level. This knowledge may then potentially lead to other strategies to reset the immune system that do not require such intensive chemotherapy treatments.
In this study, Dr Massey also compared the effect on the immune system of AHSCT to two other pharmacological treatments which cause a more selective removal of parts of the immune system and a selective regrowth, these were Alemtuzumab (Lemtrada) and Cladribine (Mavenclad).
By combining the existing data Dr Massey was able to compare the timeframes and the degree by which the different types of immune cell levels fell and how long they took, and in fact whether, they regrow to normal levels following the different treatments.
The immune cells in question are known as lymphocytes which are small white blood cells. Primarily lymphocytes are divided into B and T cells, and each type of lymphocyte can be further categorised based on function. Some of the cells promote and direct an immune response whereas others dampen down a response, they all work together in unison to produce an effective immune system.
Each of the treatments Dr Massey looked at depleted some or all of these lymphocytes to different levels, and the different lymphocytes took different times to recovery. Additionally, the growth pattern and level of recovery of these cells were different for each treatment with alemtuzumab treatment leading to some B cells recovering to a higher level than before treatment. This information could give us a vital understanding of the interplay between these cells in the autoimmune process and also explain some of the potential side effects of these treatments.
Dr Massey’s own research, funded through her MS Research Australia PhD scholarship is looking at the blood samples of Australian people with MS taken before and after they received AHSCT. She is examining the numbers and types of T cells present following AHSCT and whether this can be used to predict which patients will have the most long-term benefit from the treatment.
Dr Massey’s work will help contribute to the worldwide understanding of AHSCT, and what role it might play in the MS treatment landscape.