Final answer:
MHC class II molecules bind to CD4+ T cells, also known as helper T cells, which are essential for initiating and regulating immune responses.
Step-by-step explanation:
MHC class II molecules bind to CD4+ T cells, which are also known as helper T cells (TH). These cells play a critical role in the immune system by regulating immune responses through interaction with other types of immune cells. Specifically, MHC class II molecules are found on professional antigen-presenting cells (APCs) such as macrophages, dendritic cells, and B cells. They present abnormal or nonself pathogen antigens to CD4+ T cells for the initial activation of these T cells. Upon recognition of these antigens, naive CD4+ T cells are stimulated to become helper T cells, which then assist in activating other immune cells or secrete cytokines to orchestrate a broader immune response.