Vaccines are designed to mimic an infection, prompting the immune system to respond without causing disease. When a vaccine is administered, it introduces an antigen (a piece of the pathogen, such as a protein or a weakened virus) into the body. This antigen is recognized by antigen-presenting cells (APCs), which process it and present it on their surface to T cells.
Helper T cells (CD4+) recognize these antigens and become activated. They then help activate B cells to produce antibodies and also activate cytotoxic T cells (CD8+), which can kill infected cells. This coordinated response helps the body develop immunity to the pathogen.
