How Immune System Works

Introduction

• The immune system is the body's defense mechanism against foreign invaders, such as viruses and bacteria, that can cause infections or diseases.

Components of the Immune System

1. White Blood Cells

• White blood cells, also known as leukocytes, are the main cells involved in the immune response. There are several types of white blood cells, including: a. T cells, also known as T lymphocytes, are responsible for cell-mediated immunity. They directly attack infected cells and help regulate the immune response. b. B cells, also known as B lymphocytes, produce antibodies, which are proteins that recognize and neutralize foreign invaders. c. Natural Killer (NK) cells, which recognize and kill infected cells and cancer cells. d. Monocytes and macrophages, which engulf and digest foreign invaders and debris.

2. Antibodies

• Antibodies are proteins produced by B cells in response to an antigen, which is a foreign substance. Each antibody is specific to a particular antigen and can recognize and neutralize it.

3. Complement System

• The complement system is a group of proteins that work together to enhance the immune response. They can attract white blood cells to the site of infection, stimulate inflammation, and help to destroy foreign invaders.

4. Lymphatic System

• The lymphatic system is a network of tissues, organs, and vessels that help to circulate fluid, lymph, throughout the body. Lymphocytes are produced and mature in the lymphatic tissues, including the bone marrow and thymus, before entering the bloodstream.

The Immune Response

1. Recognition

• The first step in the immune response is recognition of the foreign invader. White blood cells and antibodies recognize antigens on the surface of viruses, bacteria, and other foreign invaders.

2. Activation

• Once a foreign invader is recognized, the immune system is activated. T cells and B cells are stimulated to multiply and differentiate into effector cells, which carry out the immune response.

3. Attack

• The immune system attacks the foreign invader in several ways: a. T cells directly attack infected cells, either by releasing toxic substances that kill the infected cell or by marking the infected cell for destruction by other immune cells. b. B cells produce antibodies that recognize and neutralize the foreign invader. c. The complement system enhances the immune response by attracting white blood cells to the site of infection, stimulating inflammation, and helping to destroy the foreign invader. d. Macrophages engulf and digest foreign invaders and debris.

4. Memory

• After the foreign invader has been cleared, some immune cells remain in the body as memory cells. If the same invader is encountered again, the memory cells will quickly recognize and respond, leading to a more rapid and effective immune response.

Conclusion

• The immune system is a complex network of cells, tissues, and organs that work together to protect the body from foreign invaders. Through recognition, activation, attack, and memory, the immune system is able to effectively defend against infections and diseases.