Describe autoimmune disease

Describe pathogenesis of autoimmune disorders

Define immunologic deficiency syndromes

Learning Objectives cont..

Immunology: Is the study of body defence mechanisms.

Immunity is the way in which the body can protect itself from invasion by pathogenic micro-organisms and provide a defence against their harmful effects

Immune responses: is the body’s ability to stay safe by affording protection against harmful agents and involves lines of defense against most microbes as well as specialized and highly specific response to a particular offender

Adaptive immunity; refers to antigen-specific defense mechanisms that take several days to become protective and are designed to remove a specific antigen.

Innate immunity; This is the body’s first line of defense against germs that entering the body.

Definitions of Terms cont..

Immune system is divides into two groups

Natural immunity(non-specific): Is provided by all the mechanisms that form an immediate non specific barrier to infection

Artificial immunity (specific): refers to all the mechanisms that are involved when the body actively responds to a foreign substance as an infecting micro organism

IgG (gamma heavy chain)

Consist of one sub unit and has two Ag combining sites

Found in blood and tissue spaces.

Crosses placenta barrier

Its pre-dominant in the circulating system(major)

Secondary line of protection

IgM (mu heavy chain)

Consists of 5 subunits

Has 10 antigen binding sites

Found in blood circulation

Its the main antibody formed after infection(primary response )

IgA (alpha heavy chain)

Consists of 2 subunits with 4 antigen binding sites

Found in body secretions. eg eyes, skin, grands

IgE (Epsilon heavy chain)

Found in tissue and little in blood

Its found in high quantities in patients with parasitic infection, asthma or allergic reactions

IgD (delta heavy chain)

Function is not clear.

Found in leukemic patients

Has short half life in serum

Major components of innate immunity includes

Physical barriers( like the skin)

Chemicals barriers( such as stomach acid and enzymes)

Cellular barriers(like white blood cells)

Proteins like complements and interferons

These components work together to provide a rapid, non-specific defense against a wide range of pathogens.

This is the first line of the body defence mechanism.

It consists of the following;

1, Mechanical barriers

This includes skin, lining of the gut, mucosa of the respiratory tract and genital areas. Nasal hairs act as filters. The action of coughing and sneezing removes the micro- organism.

Chemical barrier

These are secretions that consists substances whish have anti-microbial actions. Examples; lysosomes found in eyes, genital areas, respiratory tract, The salty fatty acid, sebum found in skin secretions, blood, HCL in the stomach and tissue components(complement).

Phagocytosis

This is when a cell called a phagocyte engulf and destroys an organism or other foreign body by digestion with enzymes contained in its cytoplasmic granules.

Antimicrobials commensal flora

These are commensal flora protecting the body from infection by stopping growth of potential pathogenic organisms by;

Occupying the attachment Site.

competing for essential nutrients

Producing substances antagonistic to other bacteria e.g. Colicines.

Common immunological reactions is

Hypersensitivity reaction

Autoimmune disorder

Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. They are usually referred to as an over-reaction of the immune system and these reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized (immune) state of the host.

Hypersensitivity reactions are classified into four types ( Type I to Type IV) based on the immune mechanisms involved and the time it takes for the response to occur.

type

Antibody or cell mediator

Immunological reaction

disorders

I

Antibody IgG

Fast response which occurs in minutes, rather than multiple hours or days. Free antigens cross link the IgE on mast cells and basophils which causes a release of vasoactive biomolecules

Asthma and anaphylaxis

II

Antibody IgG and IgM

Antibody (IgM or IgG) binds to antigen on a target cell, which is actually a host cell that is perceived by the immune system as foreign, leading to cellular destruction

Thrombocytopenia and autoimmune hemolytic anemia

III

Antibody IgG and complement

Antibody (IgG) binds to soluble antigen, forming a circulating immune complex. This is often deposited in the vessel walls of the joints and kidney, initiating a local inflammatory reaction

Serum sickness

Rheumatic arthritis

IV

Cells(T-cell)

T helper cells are activated by an antigen presenting cell. When the antigen is presented again in the future, the memory T-cells will activate macrophages and cause an inflammatory response. This ultimately can lead to tissue damage

dermatitis

allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include

hay fever,

food allergies,

atopic dermatitis,

allergic asthma,

and anaphylaxis.

Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling. Food intolerances and food poisoning are separate conditions.

Early exposure to potential allergens may be protective. Treatments for allergies include avoiding known allergens and the use of medications such as steroids and antihistamines. In severe reactions injectable adrenaline (epinephrine) is recommended. Allergen immunotherapy, which gradually exposes people to larger and larger amounts of allergen, is useful for some types of allergies such as hay fever and reactions to insect bites. Its use in food allergies is unclear.

Type I Hypersensitivity( immediate hypersensitivity)

Mechanism; involves IgE antibodies

Timing; immediate, occurring within minutes of exposure

Examples; Allergies like hay fever, asthma and anaphylaxis.

Types of hypersensitivity

Mechanism; involves IgG or IgM antibodies targeting cells.

Timing; generally not immediate

Examples; Blood transfusions reactions, immune diseases like hemolytic anemia.

Types of hypersensitivity

Mechanism; involves immune complexes (antigen-antibody aggregates)

Timing; typically not immediate.

Examples; Rheumatoid arthritis, systemic lupus erythematosus.

Types of hypersensitivity

Mechanism; involves T cells and macrophages.

Timing; delayed, occurring 24 hours or more after exposure.

Examples; contact dermatitis (e.g. poison ivy reaction), some autoimmune diseases)

Each type reflects a different aspect of the immune response and can lead to various clinical conditions.

Types of hypersensitivity

Autoimmune diseases occurs when the immune system, which is designed to protect the body from harmful substances, mistakenly attacks its own cells, tissues and organs. This can lead to inflammation and damage. The exact cause of autoimmune disease is often unclear but a combination of genetic, environmental and hormonal factors may contribute.

Examples of autoimmune diseases include rheumatoid arthritis, lupus, type 1 diabetes and multiple sclerosis. Symptoms vary depending on the specific condition but often involve chronic inflammation, fatigue and damage to the affected tissues or organs. Treatment typically involves managing symptoms and suppressing the immune response to prevent further damage.

Autoimmune diseases are chronic and may require long term medical attention.

Autoimmune diseases cont..

The pathogenesis of autoimmune disorders involves a complex interplay of genetic, environment and immunological factors. Here’s a simplified overview:

Genetic predisposition: individual with a family history of autoimmune disease may have a genetic predisposition. Specific genes associated with immune regulation and self-tolerance can influence susceptibility.

Environmental triggers: exposure to a certain environmental factor, such as infections, toxins or stress, may trigger autoimmune responses. Molecular mimicry, where foreign substances resemble self-antigen, can confuse the immune system.

Loss of tolerance: normally. The immune system has mechanism to distinguish between self and non-self antigen. In autoimmune diseases, there is a breakdown in immune tolerance, nad the body begins to attack their own cells.

Activation of immune response: antigens from the body’s own tissues become target for the immune cells. Autoantibodies( antibodies against self) and autoreact T cells are produced, leading to inflammation.

Tissues damage and inflammation: immune cells target and attack healthy tissues, causing inflammation and damage. This can result in chronic, progressive conditions affecting various organs or systems

The specific mechanisms can vary among different autoimmune disorder but this general processes illustrates how acombination of genetic susceptibility and environmental triggers can lead to the development and progression of autoimmune diseases.

Immunological deficiency syndrome also known as immunodeficiency disorders, refer to a group of conditions characterized by a weakened or compromised immune system. In these disorders, the immune system is unable to effectively protect the body from the infections and diseases, making affected individual more susceptible to recurrent or several infections.

This is the second line of defence mechanism after the natural. It is divided into

Active acquired immunity

This is when the body actively responds to a foreign substance or micro- organism by producing antibody

The immunity is produced as a result of antigenic stimulation. e.g. infections, antibody or cell mediated (T and B cells) and vaccination

This is when antibodies formed from another human or animal are introduced into the body.

This gives the body protection against foreign substance or micro-organism.

It occurs naturally with passage of certain antibodies across the placenta to the foetus and also the transfer of maternal antibodies in breast milk after birth.

Eg -milk from mother to child

Blood transifusion

An autoimmune disease is a condition in which the body immune system mistakenly attacks the body.

In an autoimmune disease, the immune system mistakes part of your body, like your joints or skin, as foreign. It releases proteins called auto antibodies that attack healthy cells

Immune system disorders cause abnormally low activity or over activity of the immune system. In cases of immune system over activity, the body attacks and damages its own tissues (autoimmune diseases). Immune deficiency diseases decrease the body’s ability to fight invaders, causing vulnerability to infections.

In response to an unknown trigger, the immune system may begin producing antibodies that instead of fighting infections, attack the body’s own tissues. Treatment for autoimmune diseases generally focuses on reducing immune system activity. Examples of autoimmune diseases include:

Addison disease

Celiac disease – sprue (gluten-sensitive enteropathy)

Dermatomyositis

Graves disease

Multiple sclerosis

Pernicious anemia

Reactive arthritis

Rheumatoid arthritis

Type I diabetes

The blood cells in the body’s immune system help protect against harmful substances. Examples include bacteria, viruses, toxins, cancer cells, and blood and tissue from outside the body. These substances contain antigens. The immune system produces antibodies against these antigens that enable it to destroy these harmful substances.

When you have an autoimmune disorder, your immune system does not distinguish between healthy tissue and potentially harmful antigens. As a result, the body sets off a reaction that destroys normal tissues.

The exact cause of autoimmune disorders is unknown. One theory is that some microorganisms (such as bacteria or viruses) or drugs may trigger changes that confuse the immune system. This may happen more often in people who have genes that make them more prone to autoimmune disorders.

An autoimmune disorder may result in

The destruction of body tissue

Abnormal growth of an organ

Changes in organ function

An autoimmune disorder may affect one or more organ or tissue types. Areas often affected by autoimmune disorders include:

Blood vessels

Connective tissues

Endocrine glands such as the thyroid or pancreas

Joints

Muscles

Red blood cells

Skin

treatments can’t cure autoimmune diseases, but they can control the overactive immune response and bring down inflammation or at least reduce pain and inflammation. Drugs used to treat these conditions include: nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Motrin, Advil) and naproxen