Question

how breakdown in immune cells' functions can lead to disease/disorders, etc.).

Answer 1

The immune system is essential for survival of an individual . Without an immune system, our body will face attack from pathogens such as bacteria, viruses, parasites, and more. It is our immune system that protect s us from various diseases.

The immune system is a host defense system comprising many biological structures and processes within an organism that protects against disease. The immune system is made up of special organs, cells and chemicals that fight infection (microbes). The main parts of the immune system are: white blood cells, antibodies, the complement system, the lymphatic system, the spleen, the thymus, and the bone marrow.most immune cells are produced from the bone marrow.

1. White blood cells are also called leukocytes. They circulate in the body in blood vessels and the lymphatic vessels that parallel the veins and arteries.

White blood cells are on constant patrol and looking for pathogens. When they find a target, they begin to multiply and send signals out to other cell types to do the same.

Our white blood cells are stored in different places in the body, which are referred to as lymphoid organs Thymus,Spleen, Bone marrow, Lymph nodes

There are two main types of leukocyte: phagocytes and lymphocytes.

Phagocytes surround and absorb pathogens and break them down, destroying them. There are several types, including:

• Neutrophils — most common type of phagocyte and attack bacteria.
• Monocytes — the largest type.
• Macrophages — these defend for pathogens and also remove dead cells.
• Mast cells — they help to heal wounds and defend against pathogens.

Lymphocytes help the body to remember previous pathogens invaded and recognize them if they come back to attack the body system.

• Lymphocytes begin their life in bone marrow. Some stay in the marrow and develop into B lymphocytes (B cells), others move to the thymus and become T lymphocytes (T cells). These two cell types have different roles:

• B lymphocytes — they produce antibodies and help alert the T lymphocytes.

  Once B lymphocytes spot the antigen, they begin to secrete antibodies or Immunoglobulin. Antibodies are special proteins that target on to specific antigens.

• T lymphocytes or CD 4 Cells — they destroy compromised cells in the body and help alert other leukocytes.

  T lymphocytes are of two types

  Helper T cells (Th cells)— they coordinate the immune response and stimulate B cells to produce more antibodies. Others attract more T cells or cell-eating phagocytes.

  Killer T cells (cytotoxic T lymphocytes) — these cells attack other cells. They are particularly useful for fighting viruses. They recognize sparts of the virus on the outside of infected cells and destroy the infected cells.

Immune system may go wrong due to many reasons

Immunodeficiencies

Immunodeficiencies can be caused due to advancing age, obesity, infections and alcoholism. In developing countries, malnutrition is the most common cause. Decrease of CD4 T cells predisposes humans to opportunistic infections. In adults, HIV is certainly the most common cause of CD4 lymphocytopenia, but other causes, such as , autoimmune diseases, immunosuppressive therapy,and lymphoma.

AIDS is an example of an acquired immunodeficiency. HIV, which causes AIDS, is an acquired viral infection that destroys important white blood cells and weakens the immune system. People with HIV/AIDS become seriously ill with infections that most people can resist with.These are called opportunistic infections ..

In some cases, immunodeficiencies can be inherited in disease such as chronic granulomatous disease where phagocytes do not function properly. In cancer patients due to chemotherapy cells gets destroyed and immune system weakens.

Autoimmunity

In autoimmune conditions, the immune system targets healthy own cells of the body , rather than foreign pathogens or faulty cells. In this scenario, they cannot distinguish own cells from other cells.

Autoimmune diseases include celiac disease, type 1 diabetes, rheumatoid arthritis,Myathenia gravis and Graves’ disease.

Hypersensitivity

In hypersensitivity, the immune system overreacts in a way that damages healthy tissue. Example is anaphylactic shock where the body reacts to an allergen in a life-threatening manner.

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