PATHOLOGY

Detailed explanation-1: -The cells of the immune system continuously flow through the body, looking for germs that may be invading the body. The immune system recognizes invaders by their antigens, which are proteins on the surface of the invading cells (see Figure 1).

Detailed explanation-2: -Innate immune cells recognize certain molecules found on many pathogens. These cells also react to signaling molecules released by the body in response to infection. Through these actions, innate immune cells quickly begin fighting an infection. This response results in inflammation.

Detailed explanation-3: -Adaptive immune responses are carried out by white blood cells called lymphocytes. There are two broad classes of such responses-antibody responses and cell-mediated immune responses, and they are carried out by different classes of lymphocytes, called B cells and T cells, respectively.

Detailed explanation-4: -There are two types of leukocytes: phagocytes and lymphocytes. Phagocytes engulf the intruders, break them down and chew them up. Lymphocytes are further broken down into two more types. The B lymphocytes (or B-cells) create antibodies and alert the T lymphocytes (or T-cells) to kill the pathogens.