Table 3.

Main findings of clinical studies.

No	Author	Main results
1	Mihara	• In peripheral lymphocytes: the percentage of NK cells (CD3-CD56+) of the PD group was higher • NK activity was not significantly different between the PD and HC groups; • The correlation between NK activity of PD patients and disease duration was positive; • The percentage of NKG2A+ cells among CD3-CD56+ NK cells in the PD group was statistically lower; • No significant difference between both groups in the percentage of NKG2D+ cells amongCD3-CD56+ NK cells
2	Niwa	• In peripheral lymphocytes: the percentage of CD16+ and CD56+ cells was significantly higher in patients with PD • No significant difference between both groups in the NK cell activity; • The percentages of CD16+ and CD56+ cells were not correlated with the UPDRS and UPDRS III score;
3	Stevens	In PBMC: no changes in the numbers of CD56+ cells in PD patients
4	Cen	In PBMC: • The percentage of NK cells in peripheral blood from PD patients was higher than that from the control group; • The percentage of NK cells did not differ between the early-onset groups and the late-onset group
5	Sun	In peripheral blood lymphocytes: • The percentage of NK cells (CD3-CD16+CD56+) in PD patients was significantly higher than that in healthy controls; • People with NK cells deviating from the reference range had an increased risk of PD
6	Anderson, K. M.	• High expression KIR3DL1 alleles in combination with HLA-Bw4/Bw4i reduce gait difficulties and rigidity in Parkinson's disease; • Weak KIR3DL1/HLA interactions associate with higher risk of rigidity and lower risk of resting tremor; • High-expressing KIR3DL1*002 is at higher frequency in patients who present with symptoms related to movement
7	Huang	• The fraction of resting NK cells in PD was significantly higher • NK cell mediated cytotoxic pathways were enriched in PD; • The mRNA level of prostaglandin D2 synthase (PTGDS) was positively correlated with the fraction of resting NK cells
8	Konstantin Nissen	An increase in CD16 median fluorescence intensity (MFI) on the mature NK cells(CD3-CD56dimCD16+)during early PD (within 5 years of diagnosis);
9	Tian	In PBMC: • C32 (CD56+CD16+CD57-CD28-) cluster and C27 (CD56+CD16+CD57+CD28-) cluster increased in PD patients compared to those in HCs and both increased in patients with LOPD compared to those in EHCs; • C29 (CD56+CD16+CD57+CD28+) cluster was lower in patients with PD with no significant difference • Increase in C32 NK cells was associated with increased UPDRS and UPDRS-III scores, but decreased MMSE scores of PD patients;