Pathology Of Immune System Question And Answers

Diseases Of The Immune System Important Notes

1. Hypersensitivity reactions

Diseases Of The Immune System Long Essays

Question 1. Define hypersensitive reaction. Explain type IV hypersensitive reaction.
Answer:

• Hypersensitivity or allergy is defined as a state of exaggerated immune response to the antigen, which may lead to tissue damage, disease or even death following contact with specific antigens.
• Lesions of hypersensitivity i.e., immunologic tissue injury are produced due to the interaction between antigen and product of immune response.
• Depending upon the rapidity, duration, and type of immune response, hypersensitivity reactions are classified into.

1. Immediate type:

It includes 3 types.

1. Type 1 – Anaphylactic reaction.

• Example: Systemic anaphylaxis/local anaphylaxis.

2. Type 2 – Cytotoxic reaction.

• Example: Erythroblastosis fetal, leucopenia.

3. Type 3 – Immune complex-mediated reaction

• Example: Arthritis and skin diseases.

2. Delayed type:

Type 4- Hypersensitivity reaction.

Type 4/delayed hypersensitivity reaction is tissue injury by cell-mediated immune response without the formation of antibodies but is instead a slow and prolonged response of specifically sensitized T- lymphocytes.

Etiology and pathogenesis: Type 4 reaction involves the role of most cells and basophils, macrophages and CDQ + T cells. The mechanism of type 4 reaction is:

• The antigen is recognized by CDg + T cells (cytotoxic T cells) and is processed by antigen-presenting cells.
• Antigen-presenting cells migrate to the lymph node where antigen is presented to helper T-cells (CD4 + T cells).
• Helper T cells release cytokines that stimulate T cell proliferation and activate macrophages.
• Activated T cells and macrophages release pro-inflammatory mediators and cause cell destruction.

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Examples:

• Reactions against mycobacterial infection.
  • Examples: Tuberculin reaction, granulomatous reaction in tuberculosis, leprosy.
• Reaction against virally infected cells
• Reaction against malignant cells in the body.
• Reaction against organ transplantation example transplant rejection, graft versus heart reaction.

Diseases Of The Immune System Short Essays

Question 1. Anaphylaxis
Answer:

• Anaphylaxis or type I hypersensitivity is defined as a state of rapidly developing an immune response to an antigen (i.e., allergen) to which the individual is previously sensitized.
• The reaction appears within 15-30 min of exposure to antigen.

Anaphylaxis Etiology: Type I reaction is mediated by humeral antibodies of IgE type or regain antibodies in response to antigen.

The definite cause is not known, but the following may be responsible.

• Environmental pollutants
• Genetic basis
• Concomitant factors – Allergic response may be linked to the occurrence of certain viral infections of the upper respiratory tract.

Anaphylaxis Pathogenesis: Type 1 reaction includes the participation of B lymphocytes and plasma cells, mast cells and basophils, neutrophils, and eosinophil It mechanism is:

• During first contact, with antigen, sensitization takes place.
• During the second contact, IgE antibodies on the surface of mast cells – basophils are firmly bound to FQ receptors and set in cell damage and degranulation of mast cells occurs.
• Released granules contain important chemicals and enzymes with pro-inflammatory properties – histamine, serotonin, vasoactive, intestinal peptide, prostaglandins, platelet-activating factor, etc. The effects of these agents are.
  • Increased vascular permeability
  • Smooth muscle contraction
  • Vasoconstriction followed by vasodilation
  • Shock
  • Increased gastric secretion
  • Increased nasal and lacrimal secretions
  • Eosinophilia and neutrophilia.

Anaphylaxis Examples:

• Reactions against mycobacterial infection.
  • Examples: Tuberculin reaction, granulomatous reaction in tuberculosis, leprosy.
• Reaction against virally infected cells
• Reaction against malignant cells in the body.
• Reaction against organ transplantation example, transplant rejection, graft versus host reaction.

Diseases Of The Immune System Short Question And Answers

Question 1. Atopy
Answer:

• Atopy is a form of type I hypersensitivity reaction
• The antigens commonly involved in it are pollens, house dust, and food
• These induce IgE antibodies

Atopy Features:

• Atopy shows marked familial distribution
• Atopy sensitization is developed spontaneously following natural contact with opens
• The reaction occurs at the site of entry of antigen
• For example
  • Inhalation of pollens affects the lungs
  • Contact leads to local allergy

Atopy Manifestations:

• Conjunctivitis
• Rhinitis
• Bronchospasm
• GI symptoms
• Dermatitis
• Cutaneous eruptions

Question 2. B lymphocytes
Answer:

• Lymphocytes are of 2 major types. B lymphocytes (10 – 15% of T lymphocytes (75 – 80%).
• Lymphocytes undergo maturation and differentiation in the bone marrow and form B cells.
• B cells are involved in humeral immunity by inciting antibody response.
• On coming in contact with an antigen, B cells are activated to proliferate and transform into plasma cells.
• Depending upon the maturation stage of B cells, specific CD molecules appear on the cell surface which can be identified by CD markers, common B cell markers include CD 19, 20, 21, 23.
• These cells also possess B cells receptors for surface immunoglobulin (IgM and IgG) and FQ receptors for attaching to antibody molecules.

Question 3. Cell-mediated immunity
Answer:

• It is also known as type 4 delayed hypersensitivity re-action.
• It is defined as tissue injury by cell-mediated immune response without the formation of antibodies but is instead a slow and prolonged response of specifically – sensitized lymphocytes.
• The reaction occurs about 24 hours after exposure to antigen and the effects is prolonged which may last up to 14 days.

Question 4. Routes of transmission of HIV
Answer:

Routes of transmission:

The virus is present in the body fluids like blood, lymph, and genital fluids and gets transmitted when a healthy individual’s body fluids come in contact with an affected individual.

• Sexual transmission: This is the commonest form of transmission.
• Transmission via blood and blood products: Next commonest form.
• • Intravenous drug abusers: By sharing needles, syringes, etc.
  • Hemophiliacs: Who received large amounts of factor 8 concentrates.
  • Recipients of HIV: Infected blood and blood products.
• Perinatal transmission: It is also called vertical transmission, which occurs from the infected mother to the newborn during pregnancy or through breast milk.
• Occupational transmission occurs in workers engaged