There are many reasons why you, in some future year, may want to destroy your immune system and replace it with a new one. It's not an unreasonable goal, given that medical researchers are already doing just that in clinical trials aimed at curing automimmune conditions. The reason I have in mind - exhaustion of immunological space and effectiveness due to a lifetime of cytomegalovirus exposure - occurs to all of us, is a contributor to the degenerations of aging, and is outlined in detail back in the Fight Aging! archives.
One main reason your immune system fails with age appears to be that chronic infections by the likes of cytomegalovirus (CMV) cause too many of your immune cells to be - uselessly - specialized. ... researchers are looking into a possible way of clearing these infections from the body.
The flip side of clearing out CMV is to reboot your immune system. Clean it out and start afresh, absent the clutter of memory cells devoted uselessly to CMV that were crowding out the naive T cells needed to respond to new threats. There's more to the aging of the immune system than just this process of crowding, but it's a good start.
Here's an example of some of the foundational work that could lead to safe reconstruction of an age-damaged immune system:
A new study demonstrates for the first time that embryonic stem cells [ESCs] can be used to create functional immune system blood cells
In this study, a team of scientists from Iowa, Taiwan, and Germany used HOXB4-containing ESCs to engraft the bone marrow and rescue mice that genetically lacked any immune system and had been irradiated to destroy their bone marrow. Only cells containing HOXB4 were able to engraft, rescue the mice, and produce blood cells long term. These engrafted cells were shown to be derived from the transplanted ESC-derived cells.
To determine if these transplants were able to rebuild the defunct immune system, the scientists injected the mice with LCMV, a common rodent virus, and watched for T-cell activity, a sign that the body was defending itself against the infection. Although the number of T cells generated by the new hematopoietic cells was low, they were able to respond effectively to the virus. In addition, the transplanted hematopoietic cells were also able to produce B cells and other defensive cells called antigen-presenting cells, which have a role in signaling T cells to action. They also tested the ability of the mice to respond to vaccination and demonstrated the induction of specific immune cells. Although the level of immune response was not what is seen in normal adult mice after exposure to the virus or vaccine, it was measurable and effective.
A way to go yet, but that's progress.