In immunohistochemical staining technique, the primary antibodies should be raised in a species different from the tissue being stained. If mouse primary antibodies are used on mouse tissues, an anti-mouse IgG secondary antibody may bind to all the endogenous IgG in the mouse tissue, leading to high background. Under this circumstance, special immunodetection kits should be used to distinguish between the mouse primary antibody and the endogenous mouse immunoglobulins. In our previous experiment, we applied a murine anti-enterovirus 71 antibody to detect the distribution of enterovirus 71 in an EV71 infected mouse model, and EV71 antigen was detected in the skeletal muscle. However, a same result was observed when PBS replaced the anti-enterovirus 71 antibody, it is also positive but light background. Therefour, we propose that anti-mouse IgG secondary antibody can directly bind to EV71 antigen.(This study was supported by Specialized Research Fund for the Doctoral Program of Higher Education of China, 20124433110009, and also by Guangdong Natural Science Foundation of China, S2012010009540; Corresponding Author: Hong SHEN)