A semi-privileged status for rat skin allografts may be achieved by placing them on extensive open beds formed by panniculus carnosus muscle which prevents contact of the transplant with host skin. Such allografts enjoy approximately a twofold increase in their life expectancy, even if transplanted across a strong histocompatibility barrier. Experiments are described which rule out stress or a "central" weakening of response, such as enhancement, as explanations of this phenomenon.
Intact skin "islands" separated from surrounding host skin on all sides by a broad border of bared panniculus were also found to serve as privileged sites. Dye injected into these islands failed to reach the regional nodes until about the 15th day after their preparation. These studies indicate that a lymphatic deficit is responsible for the observed privileged status of the allografts.