Final answer:
The MHC type that presents processed peptides to T cells and is found on macrophages is MHC-II, which is exclusively expressed on antigen-presenting cells including macrophages, dendritic cells, and B cells.
Step-by-step explanation:
The type of major histocompatibility complex (MHC) that presents processed peptides to T cells and is commonly found on macrophages is MHC-II. MHC-II molecules are expressed exclusively on the surface of antigen-presenting cells (APCs) such as macrophages, dendritic cells, and B cells. These cells present abnormal or nonself pathogen antigens for the initial activation of T cells, and the presentation with MHC-II is essential for the immune response. In contrast, MHC-I molecules are found on all nucleated cells and present antigens to effector T cells involved in cellular immunity, including normal self-antigens and those from abnormal or nonself pathogens.