Antigen Presenting Cells (APCs) are crucial components of the immune system. They capture, process, and present antigens—substances that can provoke an immune response—on their surface. This presentation is typically done using molecules called Major Histocompatibility Complex (MHC) proteins, which help T cells recognize and respond to pathogens. APCs include various cell types, such as dendritic cells, macrophages, and B cells. By presenting antigens to T cells, they play a vital role in initiating and regulating the adaptive immune response, ensuring the body can effectively fight off infections and diseases.