IMMUNOLOGY

Detailed explanation-1: -As previously mentioned, T cells require the action of APCs (usually dendritic cells, but also macrophages, B cells, fibroblasts and epithelial cells) to recognize a specific antigen. The surfaces of APCs express a group of proteins known as the major histocompatibility complex (MHC).

Detailed explanation-2: -Macrophages may just passively concentrate and focus antigen and increase its ability to bind and activate lymphocytes. They may produce factors that can enhance lymphocyte reactions. There is indirect evidence that macrophages may also actively process the antigens and either increase or decrease their immunogenicity.

Detailed explanation-3: -Myeloid cells, including macrophages and dendritic cells, represent an important first line of defense against infections. Upon recognition of pathogens, these cells undergo a metabolic reprogramming that supports their activation and ability to respond to the invading pathogens.