063 Study on vibrissa immune privilege of mouse

Akio Nagase, Naoya Sato, Hiromi Tsuboi, Takao Fujimura, Norio Katsuoka Dept. of Dermatology, Kitasato University School of Medicine, Kanagawa, Japan

Purpose: Hair follicles are a tissue having immune privilege with the absence of MHC-Class I antigen expression. They are, however, known to be rejected when allografted between humans. A study reported recently indicates that a certain part of the hair follicle does not cause rejection when allografted between humans. The region that facilitates hair growth was identified in that report. We conducted an experiment using the mouse vibrissa allograft system to study hair bulb immunogenicity and the function of immunocompetent cells of the host from the standpoint of the immunocompetent cell. Method: The vibrissa below the infundibulm of C57BL/6 mouse was allografted under the back skin of a group of BALB/c mice. Results were observed immunohistologically over time. The allografted vibrissa below the infundibulm was found to be rejected on Day 11. On this day, the hair bulb containing dermal papilla and dermal sheath was separated from the vibrissa of C57BL/6 mouse and allografted under the back skin of another group of BALB/c mice. on Day 11, cellular cytotoxicity was measured on the mice on which the hair bulbs were implanted using the 51Cr release assay with its spleen cell as effector cell, and EL-4, the thymoma cell strain of C57BL/6 mouse, as the target cell. Result: Classical MHC-Class I antigen was not expressed immunohistologically in the vibrissa below the infundibulm either before or after the implant. On Day 11, however, small round cells including lymphocytes had infiltrated around the implant, leading to subsequent damage, degeneration and rejection. MHC-Class I antigen was not expressed immunohistologically in the hair bulb. The spleen cells of the mice on which the hair bulbs have been grafted, possessed cellular cytotoxicity against EL-4. Discussion: The rejection and cellular cytotoxicity induction of the allograft in the hair follicle allograft system can be caused either by specific T-cell cytotoxicity that recognizes the MHC-Class I antigen of non-classical, or by non-specific NK cells which are not related to MHC-Class I antigen. This finding indicates that hair tissue may be expressing a still-unknown antigen.