How does the immune system identify foreign invaders?

The immune system identifies foreign invaders primarily through the interaction of antigens and immune cells. Antigens are unique molecules or molecular patterns found on the surfaces of pathogens, such as bacteria and viruses. When a pathogen enters the body, various immune cells, including macrophages and dendritic cells, recognize these antigens as foreign.

These immune cells then process the antigens and present them on their surface, which activates other components of the immune system, such as T cells and B cells. T cells can specifically target infected cells, while B cells produce antibodies that bind to the antigens of the pathogens, marking them for destruction and neutralization.

This coordinated response is critical for the adaptive immune system, which develops a memory of specific antigens for quicker responses upon subsequent exposures to the same pathogens. The ability of immune cells to specifically recognize foreign antigens ensures that the body can effectively defend itself against a wide range of infectious agents.

In contrast, temperature detection does not play a direct role in identifying foreign invaders, genetic sequencing relates more to understanding organismal biology than immediate immune response, and while physical barriers (like skin) serve as initial defenses, they do not identify invaders. The key aspect of identifying foreign entities lies in the specificity of antigen