Objective: To investigate the effect of Toll-like receptor 4 (TLR4) on B cell activation in β2-glycoprotein I (β2GP1)-immunized mouse models.
Methods: The healthy TLR4+/+ C3H/HeN mice and TLR4-/- C3H/HeJ mice were randomly divided into two groups: β2GP1 group and normal saline (NS) group. The mice were immunized with human β2GP1 or equal amount of NS. The primary immunization was done by subcutaneous multi-point injection. The booster immunization was performed by intraperitoneal injection and the last immunization by intravenous injection. The titer of anti-β2GP1 antibody in mouse sera was evaluated by indirect ELISA. HE staining was used to observe the changes of mouse germinal centers. The expression of CD40 ligand (CD40L) in the germinal centers was detected by immunohistochemistry. And the levels of co-stimulatory molecules CD80 and CD86 in the spleen were determined by flow cytometry.
Results: The high titer of anti-β2GP1 antibody could be detected in mouse sera following immunization with β2GP1. And the titer of the antibody in TLR4+/+ C3H/HeN mice was higher than that in TLR4-/- C3H/HeJ mice. Compared with NS group, the CD40L, CD19+CD80+ cells and CD19+CD86+ cells in C3H/HeN and C3H/HeJ mice were significantly up-regulated by the treatment of β2GPI, and the cell numbers in the C3H/HeJ mice were lower than those in the C3H/HeN mice. The germinal centers in β2GP1-immunized mice were bigger and more than those in NS group, and the number of the germinal centers in TLR4+/+ C3H/HeN mice was more than that in TLR4-/- C3H/HeJ mice.
Conclusion: TLR4 plays an important role in the process of B cell activation in β2GP1-immunized mouse models.