Virginia Online Health and Physical Education 9 (HPE 9) Practice Exam

The primary function of Helper T-cells is to trigger the production of B-cells and killer T-cells. These cells are crucial for the adaptive immune response, as they assist in coordinating the immune system's attack against pathogens. When Helper T-cells recognize foreign antigens presented by antigen-presenting cells, they become activated and release cytokines. These signaling molecules stimulate B-cells to produce antibodies that can neutralize pathogens and help activate killer T-cells, which directly attack and destroy infected or cancerous cells. This all-encompassing role in regulating and amplifying the immune response underscores the importance of Helper T-cells in maintaining an effective immune defense.

In contrast, the other options describe functions of different immune cells or responses. While some immune cells destroy infected cells directly, Helper T-cells do not perform this action themselves. Immediate immune responses are typically managed by other components of the innate immune system, and the production of antibodies is a function carried out by B-cells rather than Helper T-cells directly.