COVID-19 vaccines work by stimulating the body’s immune system to produce T-lymphocytes and B-lymphocytes. The various vaccines contain viral material that initially stimulates macrophages, which are white blood cells that attack and digest the virus, leaving behind parts of the virus recognized as antigens by the immune system. In turn, the immune system attacks the antigens by producing two defensive white blood cells, the B-lymphocytes and T-lymphocytes. Both T- and B-lymphocytes are produced in the bone marrow, whereas T-lymphocytes migrate to the thymus for maturation. Both are involved in recognizing pathogens and harmful, foreign materials in the body, such as bacteria, viruses, parasites, and dead cells.
The B-lymphocytes are defensive white blood cells that produce and secrete antibodies that attach to and destroy invading viruses and bacteria. The T-lymphocytes are another type of defensive white blood cell that have main roles that include directly killing infected host cells, activating other immune cells, producing cytokines, and regulating the immune response. The main difference between T- and B-lymphocytes is that T-lymphocytes can only recognize viral antigens outside the infected cells, whereas B-lymphocytes can recognize the surface antigens of bacteria and viruses.
