Developmental expression of C3 receptor on murine epidermal Langerhans cells during ontogeny

The developmental expression of C3 receptor, an important surface marker of murine epidermal Langerhans cells (LCs), was quantitatively studied using an immunohistochemical technique on epidermal sheets and then compared with developmental expression of Ia antigen and membrane ATPase. Anti-Mac-1 monoclonal antibody associated with CR3 was used for detecting C3 receptor and proved positive for LCs by immunoelectron microscopy. Mac-1 positive (Mac-1+) cells showed quite a different distribution from those of ATPase+ and Ia+ cells. Almost the same number of Mac-1+ and ATPase+ cells were present during the embryonic period. The number of Mac-1+ cells gradually decreased from day 1 to day 5 of postnatal life, after which they increased again. Using the double-labeling technique on epidermal sheets at day 1 of postnatal life, it was shown that Ia+ cells possessed membrane ATPase activity and some Mac-1+ cells expressed Ia antigen. On days 4 and 7 of postnatal life all Mac-1+ cells expressed Ia antigen. These findings suggest that Mac-1 antigen observed during the embryonic period gradually fades after birth and is re-expressed after day 5 of postnatal life.