With high numbers of episodes, AAU can lead to severe complications. Moreover, the risk of recurrence is different for each patient with AAU. Therefore, there is a critical and urgent need to identify patients at high risk for recurrence in order to guide personalized clinical management. In this study, we analyzed associations among 38 laboratory parameters and RFS in a large retrospective cohort of 233 patients diagnosed with AAU and identified 5 risk factors (HLA-B27, AS, HDL, LDL, and MO) significantly associated with recurrence time of AAU. Of the five risk factors, AS and HLA-B27 have been reportedly associated with AAU's pathological mechanism.
11–14 Although previous clinical studies have explored the correlation between HLA-B27 and AAU recurrence,
3,8,9 these results have been inconsistent. Pedroza-Seres et al. found that HLA-B27 positive patients had a higher frequency of recurrences than HLA-B27 negative patients.
9 However, two other studies reported that HLA-B27 positive patients have the same frequency of recurrences as HLA-B27 negative patients.
3,8 Our study provided further evidence supporting the correlation between HLA-B27 and recurrence in patients with AAU. In addition to these two well-known risk factors (HLA-B27 and AS), HDL, LDL, and MO were also found to play important roles in the prediction of AAU recurrence. HDL is positively correlated with recurrence risk, whereas both LDL and MO are negatively correlated with recurrence risk. Previous studies showed that all these factors are subject to inflammatory signal pathway, which is related to cardiovascular disease (CVD)
15 and cancer.
16 HDL is a protective factor in CVD, nonetheless LDL is a risk factor.
17–21 MO is correlated with poor prognosis in some types of cancers.
22,23 These diseases are characterized by a chronic course, which means the impact of these factors is persistent. AAU is characterized by sudden onset with limited duration, different from CVD or cancer. Chronic inflammation is harmful to the human body, whereas acute inflammation for the body means beneficial response.
24 The impact of prognostic factors in the chronic inflammatory process may be opposite to an acute inflammatory process. MO is derived from bone marrow granulocyte
-macrophage progenitor cells, which account for 4% to 5% of the total number of white blood cells in peripheral blood.
25 MO plays an important part in human immunity responses by serving as antigen-presenting immune cells, as has been reported for many autoimmune diseases.
26–28 When the human body is in an inflammatory or other unstable state, the plasma monocyte pool increases.
29,30 MO plays an important role in the pathogenesis of AAU, related to the disease activity.
31,32 Dysbiotic microbiota, possible etiology of AAU, will increase the number of MO in peripheral blood and lymph node.
11,33 Meanwhile, MO gobbles up the microbiota and presents the antigen to T cells, which is a crucial procedure in immune response. The biological properties of HDL and LDL in the human body are primarily related to cholesterol metabolism.
34 LDL accumulates cholesterol in peripheral cells, whereas HDL brings cholesterol from peripheral cells back to the liver, after which cholesterol can be excreted in the form of bile acid. Oxidized LDL promotes inflammation by activating phagocytosis.
35 HDL suppresses LDL oxidation and decreases the generation of secreted adherence factor, which has anti-inflammatory effects.
36 HDL also can compete with monocyte macrophages and bind to activated T-cell surface stimulating factors, thereby inhibiting monocyte macrophages from producing inflammatory factors.
37 However, some studies have also shown that HDL is not always associated with positive disease outcome.
38–41 In certain physical conditions, HDL may increase monocyte chemotaxis and phospholipid oxidation.
38 Apolipoprotein A-I, an important component of HDL, may be replaced by serum amyloid A, and changes, such as decreased enzymatic activity, can transform HDL into a pro-inflammatory factor.
42 There is no previous study reporting the correlation among HDL, LDL, and AAU, but studies have shown that HDL decreases during the active phase of Behcet's disease, which is another kind of uveitis.
43 HDL and LDL are probably involved in the pathogenesis of AAU.