Defences Against Pathogens

Pathogens are microorganisms that cause diseases; they include viruses, bacteria, fungi, and protozoa. Human body has a series of mechanisms to defend against these harmful pathogens.
The first line of defence is the human body’s skin; it acts as a physical barrier that prevents pathogens from entering the body.
The skin also secretes sebum, a substance that kills bacteria, and sweat, which contains enzymes that kill invading cells.
The body has mucus lining the respiratory, digestive, and reproductive systems. This sticky substance traps pathogens, preventing them from going further into the body.
In the respiratory system, the process of sneezing and coughing helps to expel pathogens out of the body.
Ingested pathogens are destroyed by the stomach acid, which is highly acidic and kills most bacteria and viruses.
If pathogens happen to penetrate these barriers, the second line of defence which includes white blood cells come into action.
White blood cells detect pathogens using proteins on their surfaces, known as antigens.
Pathogens are destroyed in two ways: Phagocytosis where phagocytes, a type of white blood cell, engulf and break down the pathogens, and by other white blood cells that produce antibodies that bind to specific antigens on the pathogen and neutralises them.
Once the body has been exposed to a particular pathogen and has made the specific antibody, the information is stored in memory cells. If the pathogen enters the body again, the immune system can respond quickly and effectively using these memory cells.
Vaccination involves injecting dead or inactivated pathogens into the body. These pathogens still have their antigens, which stimulate an immune response and the production of memory cells.
Hygiene practices like washing hands regularly, maintaining clean surroundings, and consuming safe food and water also contribute to the defence against pathogens.
Various treatments like antibiotics are used to kill bacteria, not viruses, in the body after infection. A different antibiotic is used to combat different types of bacteria.
Antiviral drugs are used to stop viruses from reproducing, slowing down the progression of a viral disease.
Antifungal medicines and antiprotozoal drugs are used to treat infections caused by fungi and protozoan pathogens respectively.

Remember, to decrease the chances of getting or spreading a disease, follow personal hygiene practices, maintain a healthy diet, and get vaccinated.