The effect of adoptive transfer of spleen cells on MPTP induced changes in microglia and dopamine neuron loss

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's and is known to afflict more than 1 million individuals over the age of 60 in United States only. One of the major challenges in treating PD is deciphering the mechanisms underlying initiation and exacerbation of dopamine (DA) neuron loss. Recent studies have also shown that apart from the role played by the innate immune system of the brain (i.e. microglial activation causing neuroinflammation) the adaptive immune system characterized by CD4+ T cells contributes to neurodegeneration in PD. In our study, we observe the effect of adoptive transfer of spleen cells previously exposed to MPTP on DA neuron and microglia. We observed that injecting the spleen cells systemically into recipient mice caused further loss of DA neurons in comparison to animals treated with MPTP only, which did not receive any spleen cells. Further, we also observed that injecting spleen cells attenuated microglial activation in MPTP treated recipients equivalent to Saline treated recipients by day 10. The infiltration of spleen cells however, was similar in all the treatment groups irrespective to the treatment that the donor's and recipients were exposed to by day 10. Thus, there is a crucial role played by the adaptive immune system, which contributed to DA neuron loss as well as in microglial activation. Thus, further studies regarding the composition of spleen cells before and after a toxin exposure at various time points may shed more light on the role played by the adaptive immune system in contributing to PD facilitating drug treatments targeting the same.