Final answer:
T-helper cells express CD4 on their surface and differentiate into various subtypes that help orchestrate immune responses by secreting cytokines.
Step-by-step explanation:
T-Helper Cells and Their Surface Markers
T-helper cells, also known as Th cells, express CD4 molecules on their surface. This expression of CD4 differentiates them from cytotoxic T cells which express CD8 receptors. Upon exposure to specific cytokines, activated T-helper cells differentiate into several subtypes including TH1, TH2, and TH17, each playing a unique role in the body's immune response. T-helper cells enhance immune defenses by secreting cytokines that act on different components of the immune system, contributing to the adaptive and innate immune responses.
The interaction of naive T cells, such as CD4+ T-helper cells, with antigen-presenting cells (APCs) via MHC II molecules is crucial for their activation and subsequent function. These activated cells then stimulate B cells or secrete cytokines to mount an effective immune response against pathogens.