A human IgM monoclonal antibody responding to HIV-infected cells too, which is characterized by lysing activated human lymphocytes, etc. under the mediation by a homologous human complement, is obtained. Using the thus obtained monoclonal antibody, it is intended to provide an immune reaction controlling remedy, etc. containing the human IgM monoclonal antibody which responds specifically to activated lymphocytes and induces cell lysis under the mediation by a homologous complement. Using the human IgM monoclonal antibody responding to activated human lymphocytes, it is also intended to provide an HIV remedy, etc. characterized by lysing and eliminating activated lymphocytes to thereby treat transplantation rejection and autoimmune diseases caused by an over-response of T lymphocytes as well as HIV infection