Final answer:
B cells, macrophages, and dendritic cells are capable of acting as professional antigen-presenting cells in adaptive immune responses, with distinct roles in stimulating T cells and initiating immune reactions.
Step-by-step explanation:
In adaptive immune responses, the cell types capable of acting as antigen-presenting cells (APCs) are B cells, macrophages, and dendritic cells. All these cells have the unique ability to process antigens and present them in association with MHC molecules, specifically to activate T cells. While B cells are not phagocytes and focus on antibody production, both macrophages and dendritic cells can phagocytize pathogens. Macrophages also promote inflammation by releasing cytokines. Dendritic cells are exceptional in capturing antigens and transporting them to lymph nodes, where they play a crucial part in initiating T cell responses. These three cell types are referred to as professional antigen-presenting cells due to their role in directly stimulating adaptive immunity.