[Infiltration of DCs and CD4+ T cells in muscle after DNA immunization].

Objective: In order to get a better understanding of the mechanism of DNA initiating specific cytotoxicity T lymphocyte (CTL) immune response, we observed the local infiltration in injection site at different time after DNA immunization and further studied the characters of infiltration cells.

Methods: The local infiltration in injection sites was observed by HE staining at 6 h, 12 h and 1-6 days after DNA immunization. Infiltration cells were further studied with the mice dendritic cells marker CD205, T lymphocyte marker CD4 and CD8 by immunohistological methods.

Results: phAFP injection into mouse muscle led to a local infiltration. Infiltrates reached peak at 3-6 days after injection and appeared in several discrete clusters within the muscles. The predominant cell types found in infiltrates were macrophage-like cells and lymphocytes. Immunohistological staining revealed CD205+ and CD4+ cells. CD4+ cells could be detected in any of the injected muscles. CD205+ cells were only seen at 24 h to day 3, appearing later and disappearing earlier than CD4+ cells. However, CD8+ immunostaining positivity could not be found.

Conclusion: Our findings indicate that the character of local infiltration after DNA immunization is different from the inflammation of injection. The recruitment of CD205+ to the injection site suggests that DCs and Th cells play an important role in DNA immunization.