Transmission electron micrograph (TEM) of an experimental HIV-antigen" vaccine for AIDS. The virus-like particles seen here are derived from yeast. They contain antigens specific to the HIV- virus. AIDS is an acquired disease of the immune system caused by the HIV-virus (Human Immunodefi- ciency Virus). The harmless virus-like carrier seen here is being tested for its effectiveness to combat the onset of AIDS. It has been labelled with antigens (proteins) which, it is hoped, will alert the body's immune system to fight the HIV- virus. As late as 1992 research had yet to uncover the mechanism by which the HIV-virus causes AIDS. Magn: x200,000 at 8x10 inch, x29,000 at 35mm size."