The lymphatic system is made up of your tonsils, lymph nodes, lymph vessels, thymus gland and bone marrow. It is a vast network of vessels that collect excess fluids — and some fats — from tissues throughout your body, and then return them to your bloodstream.
Many of the disease-fighting cells of the immune system:
- Begin in the bone marrow.
- Mature in the thymus.
- Are stored in strategic locations. (Tonsils and adenoids guard the throat and lungs, and Peyer Patches guard the digestive system.)
- Use the lymphatic “highway” system to travel through the body, and —along with the lymph nodes and spleen — filter out harmful materials and germs.
An immune response occurs when the immune system is activated and responds. This can occur when a foreign invader is detected.
I will recommend to read Janeway Chapter 1. In summary, we are constantly exposed to antigens (virus, bacteria, fungi, etc) and we have barriers to protect us: mechanical (skin, mucosal tissue, etc) Chemical (antimicrobial peptides, ph, proteases, etc) microbiological (flora) in addition to innate immune cells as macrophages, neutrophils, monocytes, etc. When the barriers are compromised and pathogens form a focus of infection (replicate and move from cell to cell) and cause tissue damage we get sick. But not for long (most of the time) the innate immune system is in top of it! and promptly the adaptatnive mechanism are activated (if the pathogen reach the replication threshold).
http://www.yourarticlelibrary.com/immunology/4-sequences-of-events-of-acute-inflammatory-response-immunology/28042
I agree with Ludmila Akhmaltdinova. I think during the defence against diseases, some white blood cell die off while some are reained. so to complete the circles, the body become sick to get antigen through medicine supply.
Huda J.B Al- Khilkhali It completely depends on the strength of a person's immunity system and the infectious ability of a particular germ or foreign particle which already entered in to the the body.
This gives an overview of the answer to the question.
https://www.roswellpark.org/cancertalk/201809/if-your-immune-system-protects-you-why-do-you-still-get-sick
Every time forigen particle enter in body it will cure the body
But the new particle get invaded as organisms around us show addaptation nd evolution too
So every time new modification so system dont remem ber its old one nd fail to kill but gradually it kill them or u take a medicine
After some time u have to change medicine also as organism memorise medicine and get resistant to it so new medicine new disease nd sickness
because of bad sanitation and poor higene of some people on the society which they accepted pathogens mutation and increased their virulence factor so they appear more aggressive for body also increased their ability to evade from immune system
in additional to that also misusing of antibiotic lead to the mutation
all that lead to form different strain of pathogen that not be recognized immune system
If Your Immune System Protects You, Why Do You Still Get Sick?
https://www.roswellpark.org/cancertalk/201809/if-your-immune-system-protects-you-why-do-you-still-get-sick
The reason is the constant interaction of biotic and abiotic pathogenic factors acting on our body, which on the other hand is defended and protected to a certain extent by the natural immune system. As the body ages, the extent of this interaction and the effectiveness of the immune system decline. however, to a large extent, the level of effectiveness of the immune system can be shaped by applying a specific, more or less healthy lifestyle, including practicing physical activity in the open air, healthy eating, caring for mental health, avoiding chemicals in the environment around us, using natural medicine, positive relationships with environment, etc. In addition, new pathogens, carcinogens, carcinogens, etc. are constantly emerging in the surrounding environment, including new variants of viruses that cause various diseases. On the other hand, an efficiently functioning immune system, not damaged by chemicals and an unhealthy way of life, quickly learns these new pathogens, creates new types of antibodies and effectively defends our body. Thanks to this, we get sick less, and if it does appear, it is characterized by a milder course.
Best regards,
Dariusz Prokopowicz
All About Immunity and the Immune System
https://www.everydayhealth.com/healthy-living/all-about-immunity-and-the-immune-system/
The Immune System and Foreign Invaders
https://unsolvedmysteries.oregonstate.edu/immune-system-and-foreign-invaders
Your immune system fights off infection and disease. It has a number of ways to detect and destroy anything it recognizes as foreign to your body, including bacteria, viruses, fungi, parasites or unhealthy cells such as cancer cells. In some people, the immune system goes into overdrive, causing the body to see its own cells as foreign and attack them. This leads to what we call autoimmune diseases, such as Crohn’s disease, rheumatoid arthritis and lupus.