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How White Blood Cells Recognize Pathogens

Anuya Waghmare
White blood cells are the body's fighter cells, and provide immunity to the body to help fight diseases. How do these cells identify or detect the pathogens that have entered the body? Here are some ways in which pathogens are recognized and destroyed by white blood cells.

Did you know?

The skin, saliva, mucus membranes, sweat, sebum, tears, and gastric acid in the stomach, are all barriers that defend the body against bacteria and other harmful organisms.
Once a pathogen enters the human body via a wound, the mouth, or other sources, a different protective mechanism takes over. They involve various types of white blood cells that are present in the blood.
The function of the white blood cells is to protect the human body from foreign infections, be it bacteria, viruses, fungi, allergies, worms, and other pathogens. Certain proteins present in the body act as pattern recognition receptors (PRRs), that identify the microbes and send out alarm signals to activate the body's immune system.
➦ The immune system of the human body is divided into two main types, namely the innate immune system and the adaptive immune system, which help detect invaders in the human body and destroy them.

Innate Immune System

➦ The non-specific or innate immune system is present in all vertebrates, and is an evolutionary and ancestral line of defense that is inherited from one's ancestors. This system helps recognize the pathogens by various ways.
➦ The carbohydrates (sugars), proteins or lipids present in various bacteria are detected by the body as foreign, which activates the immune response. The reaction is immediate, resulting in an increase in the flow of blood cells to the site of infection.
➦ Blood cells activate the phagocytosis process. Phagocytes are special cells that contain receptors on the surface to detect or bind the pathogens. They engulf microbes and use methods like reactive chemicals, destructive enzymes or acids to deactivate and kill them.
➦ Dectin-1, a receptor on the white blood cells, recognizes certain fungal cells and alerts the immune system to fight off the infection.

➦ Inflammation is an immune response by the body. It serves as a barrier, and prevents the spread of infection as well as helps in healing of wounds.

Adaptive Immune System

➦ This is the specific or acquired immune system, and comprises specialized processes and cells that help prevent the growth, as well as get rid of the pathogens. This immune system is built-up during the lifetime, and it directly attacks the microbes which have entered the body.
➦ The WBCs that are involved in this process are lymphocytes, which detect specific antigens on the foreign cells. Two types of lymphocytes - namely the B cells and T cells, that can identify and target these antigens. The antigens are toxins or enzymes produced by the microbes.
➦ B cells make antibodies to counter the effect of antigens. These antibodies are specific to counter the antigens that triggered their production. Thus, antibodies bind to specific antigens, which are then killed, engulfed, or eradicated from the body.
➦ T cells are the killer cells that are directly involved in the killing of some virus-infected cells, tumor cells, or parasites. These cells also coordinate and regulate the immunological responses of the body.
➦ These B cells and T cells act as memory cells, which are activated to respond to a previously encountered antigen. This activation is quicker and stronger to generate an immune response. Thus, over a period of time, the body adapts itself to future occurrences and challenges of this sort. This is what we know as strengthening of the immune system.
These were the main ways in which the white blood cells in the human body recognize pathogens and help get rid of them. It is an amazing and well-developed immune system that we have in place, which keeps us safe and sound, in spite of being exposed to millions of pathogens every single minute.