and pumps all create potential ports of entry for infectious organisms.
Once an infection does get into our bodies, one of the most important defenses—the white blood cell—usually goes into action. But the number of these cells is dramatically reduced by chemotherapy , radiation therapy , leukemia and bone marrow transplants. Low white blood cell counts are common in cancer patients, and as the count decreases the risk of infection increases.
Another defense mechanism is known as cellular immunity , in which specialized white blood cells called T lymphocytes attack invading organisms. But some cancers such as Hodgkin's disease can cause defects in cellular immunity, and so can chemotherapy, radiation and drugs that suppress the immune system.
Another part of the immune defense system is known as humoral immunity . Here other specialized white blood cells called B lymphocytes produce proteins— antibodies—to fight infections. This part of the system can be damaged in cases of multiple myeloma and chronic lymphocytic leukemia or when treatment requires the removal of the spleen .
We all have "resident" bacteria (called normal flora) that are usually harmless but can cause serious infection when our defenses are down. We can try to prevent infections, but nevertheless they do occur.
