Immunology

IMMUNOLOGY

The immune response is based on the ability of the immune system to distinguish between "self" and "non-self" cells. Actually, every cell in our body, carrying the same distinctive surface proteins, can be recognized as "self" and isn't normally attacked by immune cells, which all carry the same pattern of self-markers. Any "non-self" cell - known as antigen.

Immune system is the relationship between the body systems, pathogens, and immunity in the organism.

Immunology is the science that studies all the aspects of the immune system.

What is immunology?

The immune system

The lymphatic system

The immune system is a mobile, circulating system. However, there are some organs which are important to its function and lie throughout our body. They are called lymphoid organs because within them the lymphocytes grow and develop inside them. Within the immune system the following elements can be recognized: The Bone marrow is the soft tissue in the hollow center of bones and the ultimate source of all blood cells, including the immune cells.

The immune system

Small organs called lymph nodes function as an immunologic filter for the lymph and help carry it throughout the body.

The lymphatic vessels carry the lymph, a clear fluid that bathes the tissues and contains lymphocytes and other white blood cells.

The lymphatic system is an essential component of the immune system, through which the organs are connected with one another and with other organs of the body by the network of lymphatic vessels.

The lymphatic system

CELLS OF THE IMMUNE SYSTEM

Antibodies are specialized proteins that specifically recognize and bind to one particular protein, notably the surface epitope of the antigen, slowing it and making it a prey for other immune cells. Granulocytes or Leukocytes (neutrophils, eosinophils and basophils) are white blood cells important in the removal of bacteria and parasites from the body and they also use powerful enzymes. Macrophages are often referred to as antigen-presenting cells (APC) because they pick up and ingest antigens presenting them to other cells of the immune system, such as T cells and B cells. Dendritic cells originate in the bone marrow and work as antigen presenting cells (APC).

T-Cells T-lymphocytes are usually divided into two groups: T helper cells whose task is to potentiate immune responses by the secretion of factors that activate other white blood cells to fight off infection. T killer cells which directly kill certain tumor cells, viral-infected cells and sometimes parasites. They are important in down-regulation of immune responses. Natural Killer Natural killer cells kill directly certain tumors susch as melanomas, lymphomas and viral-infected cells. B Cells The main task of B cells is the production of antibodies in response to foreign proteins of bacteria, viruses, and tumor cells.

CELLS OF THE IMMUNE SYSTEM

MONOCLONAL ANTIBODIES

In 1975 Kohler and Milstein developped a technique to have antibodies secreted by single cells and they are known as monoclonal antibodies (mAb).

Monoclonal antibodies are laboratory-produced molecules engineered to enhance or mimic the immune system’s attack on non-self cells. MAb treatments are used for the treatment of immunologic diseases and as cancer therapy.

Antibodies (Immunoglobulin molecules) are multifunctional components of the immune system produced by B cells in response to invading foreign substances. During an attack, antibodies recognize epitopes of an antigen. Antibodies found in serum are produced by many plasma cells (clones).

MONOCLONAL ANTIBODIES

THE IMMUNE RESPONSE

Phagocytose (role of an antigen-presenting cell) There are 6 phases of phagocytosis:

• phagocytosis of enemy cell (antigen)
• fusion of lysosome and phagosome
• enzymes start to degrade enemy cell
• enemy cell broken into small fragments
• fragments of antigen presented on APC surface
• leftover fragments released by exocytosis

An immune response to foreign antigens requires the presence of an antigen-presenting cell (APC) (usually either a macrophage or dendritic cell) in combination with a B cell or T cell. When an APC presents an antigen on its cell surface to a B cell, the B cell is signalled to proliferate and produce antibodies that specifically bind to that antigen. If the antibodies bind to antigens on bacteria or parasites it acts as a signal for PMNs (also called granulocytes released in the bone marrow) or macrophages to engulf (phagocytose) and kill them.

The immune response

active and passive immunity

Passive immunity is provided when a person is given antibodies to a disease rather than producing them through his or her own immune system. A newborn baby acquires natural passive immunity from its mother first through the placenta and then through lactation

Active immunity can be naturally acquired by infection or artificially acquired by vaccines made from infectious agents that have been inactivated or, more commonly, from tiny portions of the antigen.

Active and Passive Immunity

BLOOD GROUPS

All blood is composed of the same basic elements. In fact, there are eight different common blood types, which are determined by the presence or absence of certain antigens (A, B, Rh) which can trigger an immune response if they are foreign to the body. In addition to the A and B antigens, there is a third antigen called the Rh factor, which can be either present (+) or absent (-). Rh negative blood is given to Rh-negative recipients, while either Rh positive or Rh-negative blood may be given to Rh positive patients.

AB

DISORDERS OF THE IMMUNE SYSTEM

Allergy is an overreaction of the body's immune system to specific substances (allergens) misidentified as harmful. Every substance can be a potential allergen. Independently from the allergen, allergic reaction symptoms vary a lot, ranging from a runny nose and watery eyes to asthma, diarrhea, hives, and even death. Certain allergens are more likely to cause life-threatening symptoms (anaphylaxis) than others. It is important to avoid a second exposure if you have had a reaction in the past. Allergy treatments consist either in blocking the immune system signals (histamines) or calming the immune system reaction (corticosteroids).

ALLERGY

HIV AND AIDS

HIV is an RNA virus, capable of infecting cells of the immune system. HIV targets T helper cells (CD4 cells), leading to their eventual death. In an untreated person, 10 billion to 100 billion new viruses are produced per day. This destruction of CD4 cells renders a patient vulnerable to unusual opportunistic infections (OIS). Most patients who die from AIDS succumb to one or more OIs. AIDS cannot be completely cured, but combinations of drugs such as nucleoside reverse transcriptase inhibitors and protease inhibitors (commonly called HAART, for highly active anti-retroviral therapy) help control viral replication, restore immune function and maintain health, even if they have a certain degree of toxicity in the long-term. Some patients have been experimentally treated with stem cell transplants that made them resistant to HIV.

HIV AND AIDS

AUTOIMMUNE DISORDERS

At the moment, there is no definitive cure for celiac disease, the only treatment is a gluten free diet

Celiac disease is an autoimmune digestive disorder in which damage to the lining of the small intestine leads to the malabsorption of minerals and nutrients. The destruction of the inner lining of the small intestine is caused by a reaction to gluten. It can cause vomiting, abdominal cramps and chronic indigestion and is often made worse by stress.

Our immune system usually protects us from diseases and infections, but in case of an autoimmune disease, it attacks healthy cells of our body, since it can't tell the difference between healthy body tissue and harmful antigens. The result is an immune response that destroys normal body tissues. This response is a hypersensitivity reaction. In autoimmune disorders, the immune system reacts to normal body tissues as if they were "non-self" substances.

AUTOIMMUNE DISORDERS

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