Objective To explore the key flora affecting the blood group IgG antibody titer.

Methods Totally, 43 students from Fudan University were recruited as healthy volunteers and their venous blood and fresh stool samples were collected from January to February 2020. Anti-human globulin gel card was used to determine the IgG antibody titers, and participants were divided into high-level and low-level groups with a cutoff point of 1:128, low IgG class anti-A antibody titer group (OALG, ≤ 128), high IgG anti-A antibody titer group (OAHG, ≥ 256), low IgG class anti-B antibody titer group (OBLG, ≤ 128), high IgG class anti-B antibody titer group (OBHG, ≥ 256). O-type blood samples were analyzed by 16S rRNA V3-4 regional sequencing analysis, and α diversity, β diversity, and Linear discriminant analysis Effect Size (LEfSe) analyses were perfomed.

Results Among the paticipants, 12 were blood type A and 17 were blood type B. No samples with antibody titer ≥ 256 were found. There were 14 cases of blood type O, and 8 cases of samples with antibody titer ≥ 256. At the genus level, there was no statistically significant difference in Shannon index (P=0.4111, 0.2278), but the relative abundance of a certain flora was significantly different between the two groups (OAHG vs OALG, OBHG vs OBLG). When the LDA value is greater than 2.0, there are 17 kinds of flora (OAHG vs OALG), and 13 kinds of flora (OBHG vs OBLG). In the OAHG group, the bacterial group with the largest LDA value is Bacteroides vulgaris and in the OBHG group, the bacterial group with the largest value of LDA is Lacetospiraceae.

Conclusions In blood type O, when comparing the high and low IgG antibody titer groups, there is no statistical significant difference in the bacterial diversity of intestinal flora at the genus level, but there are significant differences in the relative abundance of certain flora.