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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Lymphocytes and Antibodies
Your body is constantly under attack from harmful microorganisms called pathogens. Luckily, you have an amazing defence system - your immune system - which protects you from these invaders. Two key components of this system are lymphocytes (a type of white blood cell) and antibodies (special proteins that help fight infection).
Key Definitions:
There are two main types of lymphocytes:
Both types are produced in the bone marrow, but T cells mature in the thymus gland (hence the 'T'), while B cells mature in the bone marrow (hence the 'B').
Lymphocytes are like the soldiers of your immune system. They patrol your body in the blood and lymphatic system, looking for invaders. Each lymphocyte can recognise a specific antigen through special receptor proteins on its surface. When a lymphocyte encounters its matching antigen, it becomes activated and multiplies rapidly to fight the infection.
B lymphocytes are responsible for what's called the "humoral immune response" - they produce antibodies that circulate in the blood and lymph to find and neutralise pathogens.
When a B cell encounters an antigen that matches its receptor, it undergoes a remarkable transformation:
Plasma cells can produce thousands of antibodies per second! These antibodies then travel through the bloodstream to find and bind to the specific antigen they were made for.
Antibodies (also called immunoglobulins) have a distinctive Y-shaped structure that is perfectly designed for their job.
Each antibody consists of:
Antibodies help fight infection in several ways:
While B cells produce antibodies, T cells take a more direct approach to fighting infection. They're responsible for the "cell-mediated immune response".
Also called cytotoxic T cells, these directly destroy infected cells by releasing chemicals that cause the infected cell to undergo programmed cell death (apoptosis). They're particularly important for fighting viruses that hide inside cells.
These coordinate the immune response by activating B cells to produce antibodies and by helping killer T cells to develop. They're like the commanders of the immune system.
Like memory B cells, these provide long-term immunity by remembering the pathogen. If the same pathogen invades again, memory T cells can quickly multiply and mount a rapid response.
The ability of your body to resist infection is called immunity. There are different types of immunity and understanding them is crucial for medical treatments like vaccination.
This occurs when your own immune system produces antibodies in response to an infection or vaccination. It's called "active" because your body actively makes the antibodies.
Active immunity is long-lasting because memory cells remain in your body, ready to respond quickly if the same pathogen invades again.
This occurs when you receive antibodies from another source rather than making them yourself.
Passive immunity provides immediate protection but is short-lived (weeks to months) because no memory cells are formed.
Vaccines are one of the most important medical advances in history. They work by training your immune system to recognise and fight specific pathogens without you having to suffer from the actual disease.
Vaccines contain antigens from pathogens in a form that won't cause disease but will still trigger an immune response. These might be:
When you're vaccinated, your B cells produce antibodies against the vaccine antigens and form memory cells. If you're later exposed to the real pathogen, these memory cells can quickly produce large amounts of antibodies, preventing you from getting sick.
The COVID-19 pandemic saw the development of several different types of vaccines, including some using new technologies:
All these vaccines train the immune system to recognise the SARS-CoV-2 virus without causing COVID-19 disease. They demonstrate how our understanding of lymphocytes and antibodies can be used to develop life-saving medical treatments.
Understanding lymphocytes and antibodies has led to many important medical applications:
The study of lymphocytes and antibodies continues to be a vital area of medical research, with new discoveries leading to better treatments for many diseases.
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