Quantification of anti-sperm antibody and soluble MICA/MICB levels in the serum of infertile people of the Li ethnic group in China.

OBJECTIVE To investigate the presence of anti-sperm antibodies (AsAb) and the correlation between AsAb positivity and the expression of soluble major histocompatibility complex class I chain-related A and B (sMICA or sMICB) in the sera of infertile people of the Li nationality from Hainan, China. METHOD A total of 136 people (68 couples) from five villages in the Wuzhishan region, Hainan province participated in this study. Among them, 31 couples were included in the fertile group and 37 couples in the infertile group. AsAb and sMICA/sMICB levels in serum were detected by ELISA. The median sMICA/sMICB levels between and among groups were compared by Mann-Whitney rank U testing and Kruskal-Wallis H testing, and the AsAb positivity rate was compared by Pearson Chi-Square testing. Correlation analysis was performed by calculating the Spearman's rho coefficient for nonparametric data. RESULTS The serum levels for the fertile group (AsAb: 15.5 [4.0~127.0] U/ml, sMICA: 18.33 [13.30~52.40] pg/ml, sMICB: 27.72 [18.63~47.43] pg/ml) were not statistically different from those for the infertile group (AsAb: 18.0 [9.8~95.0] U/ml, sMICA: 20.95 [15.78~23.81] pg/ml, sMICB: 26.26 [18.06~61.38] pg/ml). However, grouping based on AsAb positivity revealed a statistically significant difference for the sMICA/sMICB levels (AsAb positive group: sMICA: 5.56 [4.30~17.23] pg/ml, sMICB: 16.13 [7.54~25.43] pg/ml; AsAb negative group: sMICA: 22.00 [18.05~66.13] pg/ml, sMICB: 36.51 [20.53~67.22] pg/ml; P < 0.01). These results suggest that AsAb is negatively associated with both sMICA (Spearman's coefficient, -0.475, P < 0.01) and sMICB (Spearman's coefficient, -0.381; P < 0.01). The analysis also shows that sMICA levels are positively associated with sMICB levels (Spearman's coefficient, 0.635; P < 0.01). CONCLUSION AsAb can be detected in the serum of fertile and infertile Li people. However, there appears to be limited clinical value in the conventional detection of AsAb, sMICA and sMICB in serum for diagnosing infertility. People with positive AsAb expression have lower levels of sMICA/sMICB expression in serum, which may be one mechanism by which people produce AsAb.