AIDS and Langerhans cells: CD4 antigenic site density modification evidenced by single-cell immunogold labeling

Langerhans cells (LC) are CD4-positive antigen-presenting cells within the human epidermis and thus potentially may be infected by the causative agent of AIDS (acquired immunodeficiency syndrome), called HIV (human immunodeficiency virus). Because CD4 antigens have been demonstrated to be decreased in HIV-infected lymphocytes, we wondered whether some immunologic markers of LC might be modified in seropositive patients. For this purpose, LC, obtained from clinically unaffected skin of ARC (AIDS-related complex) and AIDS patients, were subjected to anti-CD4 (OKT4) and anti-HLA class II monoclonal antibodies (anti-DR: BL1 and anti-DQ). The density of the antigenic sites/LC recognized by the antibodies was evaluated by employing the electron microscopic immunogold labeling procedure. The density of CD4 molecules/cell measured in LC of ARC and AIDS patients by direct count of gold particles bound to the cell membrane was found to be dramatically decreased among AIDS LC, whereas a small subset of ARC LC strongly expressed this antigen. In contrast, the density of HLA class II (DR and DQ) antigenic determinants was found unchanged in comparison with that of healthy donors. In addition to the quantitative modifications of the CD4 molecule expression by ARC and AIDS LC, the observation in these cell populations of several surface protrusions suggesting viral buds affords evidence that LC are a target for HIV.