Objective To observe the deposition of SIV specific immune complex in different organs at different time-points after SIV infection,and explore its possible relationship with multisystemic pathological changes in simian acquired immunodeficiency syndrome(SAIDS).Methods\ 8 SIV-infected rhesus monkeys and 1 uninfected monkey were autopsied and sampled.Serial sections were prepared,immune fluorescence staining of IgG,C3 and SIV p27 were performed,and the results were compared and analyzed.Results\ IgG,C3 and SIV p27 fluorescence expressed similarly at the same site in most monkeys,indicating the presence of SIV-specific immune complex.Among those positions,cerebral perivascular space(8/8),myocardial interstitial vessel(6/8),paracortex(5/8) and germinal center(5/8) of lymph nodes were the main sites with a higher positive rate.Their positive rates were elevated during the late phase after infection.Conclusion After SIV infection,viral specific immune complex is deposited widely,and increased remarkably with disease progression.SIV may lead to AIDS associated multisystem complication through IC deposition.Further research on it may be helpful to understand how SIV infection induces multisystem pathological changes,and it is also a promising target for developing new treatment strategy.