Immune system and infectious diseases

Living organisms are attacked by several diseases causing agents. To deal with these disease-causing agents every organismhas a system, which becomes more complex when we move froma unicellular organism (bacteria) to a multicellular organism (human). In the case of multicellular organisms, some specific cells and tissues fight against these agents.Responses can be quick or slow depending on the nature of the agent and its harmfulness. This whole system of protection against foreign invaders is known as the immune system. Our world is full of infection-causing microbes and without the immune system, it would be impossible to deal with these life-threatening diseases.

What are the causes of infectious diseases?

There can be different causes of infectious diseases:

  • Bacteria

There are several infectious diseases caused by bacteria, for example, urinary tract infection, tuberculosis, and strep throat, etc.

  • Viruses

Viruses are even smaller than bacteria and responsible for several diseases, like common cold and AIDS.

  • Fungi

Fungi are mainly responsible for skin-related diseases like athlete’s foot and ringworm. Fungi can also infect the nervous system and lungs.

How does the immune system work against infectious diseases?

The immune system cannot fight against an infection without identifying the pathogen. There are specific molecules present on the surface of pathogens, called antigens. Every pathogen has a unique group of antigens detected and distinguished by the immune system. After a pathogen is entered into the body, the immune system responds it in two different ways:

Innate immune response

It is a rapid response. Cells associated with an innate response, recognize different antigens on different pathogens. Body releases signaling molecules in response to infection which is also detected by these cells. These actions help the immune system to start to fight against infection. These cells can also help with adaptive immunity

Adaptive immune response

This response is slower as compared to the innate immune response. But it fights with pathogens in a better way. This response involves two different types of cells called B cells and T cells. In this response, some T cells help in controlling adaptive immunity, and some kill infected cells and pathogens. On the other hand, B cells produce antibodies against certain antigens. Antibodies, that are protein in nature, attach with antigens, and produce signals. These signals are detected by immune cells and pathogens are killed. One common antibody is the CRP antibody that indicates inflammation and involves in response to inflammation.

Immune system and memory cells

When the body encounters new pathogens and new antigens, it takes some time for B and T cells to respond to them. But when our body is exposed to a certain kind of pathogens, a memory is developed, so our body is prepared for the next infection of a similar kind. Some of the B and T cells produced during adaptive immune response turn into memory cells. Memory cells became a part of lymph nodes and when our body encounters similar pathogens these memory cells fight against the infection vigorously and quickly.