Final answer:
Th1 helper T cells, which bear the CD4 molecule, are primarily responsible for secreting Interferon-gamma (IFN-gamma), aiding in the cell-mediated immune response by activating other immune cells such as macrophages.
Step-by-step explanation:
The T cells that secrete Interferon-gamma (IFN-gamma) are primarily the Th1 helper T cells. These cells are a subset of the helper T cells (Th cells) that possess the CD4 molecule. Th1 cells are crucial for the cell-mediated immune response, as they secrete cytokines that can enhance the activities of macrophages and other T cells including cytotoxic T cells (Tc). While Tc cells are primarily involved in killing infected cells by releasing substances like granzymes and perforins, Th1 cells are distinguished by their role in directing the immune response against intracellular pathogens, often by secreting IFN-gamma, which can activate macrophages and promote inflammation.
On the other hand, Th2 cells, another subset of helper T cells, are responsible for driving B cell differentiation into plasma cells which produce antibodies, a process that is distinct from the role of Th1 cells. These subsets of Th cells are not differentiated by their surface molecules but by the cytokines they secrete, which orchestrate different components of the immune response.