To estimate the immunogenicity of allogeneic platelet-rich plasma(PRP) in mini-pigs.

Blood was drawn from the carotid artery of one Bama mini-pig under the sterile condition, and then centrifuged twice, first at 1 000×g for 15 min to remove red blood cells, and then at 3 000×g for 10 min to obtain PRP. One milliliter of blood was respectively drawn from the ear vein of 3 mini-pigs which were drawn from the remaining 9 mini-pigs. Allogeneic PRP gel was injected into 9 male mini-pigs′ gluteus maximus muscles bilaterally(0.5 mL of PRP in each injection site). Divided the mini-pigs into 1 week group, 2 weeks group and 4 weeks group by sortition randomization method, 3 pigs in each group. One milliliter of blood was respectively drawn from the ear vein of corresponding group 1, 2, 4 weeks after the injection, and then mini-pigs were sacrificed and the muscle samples from injection site was obtained at each time point. The change of CD4⁺ and CD8⁺ T lymphocyte subpopulation were detected and compared through flow cytometry. Histomorphological changes and immunohistochemical analysis of local tissue immunogenic responses were observed under biological microscope. Data were processed with one-way analysis of variance and Dunnett-t test.

Before the intramuscular injection of allogeneic PRP, the ratio of CD4⁺ and CD8⁺ T lymphocyte subpopulation in peripheral blood was 0.75±0.04, which respectively changed to 0.96±0.02, 0.85±0.02 and 0.79±0.02 at week 1, week 2 and week 4 after injection. The difference was statistically significant (F=37.970, P<0.001). Compared with the CD4⁺ /CD8⁺ cell ratio before the injection, there were significant differences at 1 week group and 2 weeks group respectively(P<0.001, =0.004). There were no obvious difference in CD4⁺ /CD8⁺ cell ratio bettween 4 weeks group and normal physical level. Histopathologic examination revealed that the intramuscular injection of allogeneic PRP only caused subtle inflammation and little expression of IL-2 around the injection site at week 1, which decreased at week 2 and did not persist till week 4.

Allogeneic platelet-rich plasma can cause minor local and systemic immune response in mini-pigs. The responses will get weaker and disappeared after 4 weeks.