Apodemus agrarius Pallas has been known to be a reservoir of hanta virus. But there was no report of immune organs. So this study was performed to clarify the relation between Structure and function of immune organ. In the present investigation an immunocytochemistry procedure was used to examine the distribution of T and B cell and macrophage populations in the thymus spleen and lymph nodes. Most of lymphoid organ showed decreased pattern of Ly1 positive T and IgM positive B cells. Macrophage positive cells were deceased in vivo. The present study gives an overview on the immune organ structure and function of Apodemus agrarius Pallas.