TYPE II HYPERSENSITIVITY

Ans. is ‘a’ i.e., Hemorrhagic disease of newborn

• Graves disease, Autoimmune hemolytic anemia are type II hypersensitivity reactions.
• Hemorrhagic disease of newborn is due to vitamin K deficiency.

Ans. is ‘b’ i.e., Type II

Has been explained

Ans. is ‘a’ i.e., Immune complex; ‘c’ i.e., Ig M

o Type II hypersensitivity reaction involves Ig G or Ig M antibodies bound to cell surface antigen, with subsequent complement fixation.

Type II hypersensitivity reaction (Antibody mediated)

o Mediated by antibodies directed toward antigen on cell surfaces or extracellular matrix.

o Three different antibody-dependent mechanisms involved in this type of reaction.

1. Opsonization and complement and Fc receptor-mediated phagocytosis

o Most commonly involved in Type II reaction.

o Antibodies are deposited on the surface of cells leads to :

1. Enhanced phagocytosis through Fc receptor and phagocytes (opsonization)
2. Activation of complement and generation of C3b

o C3b also acts as opsonin. It enhances phagocytosis through C3b receptor on phagocytes (opsonization). Example —*Transfusion reactions, Erythroblastosis fetalis

2. Complement and Fc receptor mediated inflammation

o In this injury is due to inflammation and not because of phagocytosis.

o It occurs when antibodies deposit in extracellular tissues such as basement membrane and matrix. o Deposited antibodies activate complement, generating by-products such as C5a

o C5a acts as chemokine for neutrophil and monocyte.

o These neutrophils and monocytes bind to deposited antibody via Fc receptors and get activated. Examples –> Glomerulonephritis, vascular rejection in organ grafts.

3. Antibody mediated cellular dysfunction

o In this, antibodies directed against cell surface receptors impair or dysregulate function without causing cell injury or inflammation.

Graves disease                                                       Myasthenia gravis

Antibodies against                                                 Antibodies to ACH receptors

TSH receptors (LATS)                                             at N.M. junction ‘1,

Activation of TSH                                                   Inhibit binding of ACH

receptors & on thyroid                                            to its receptors epithelial cells

Muscle weakness Excessive thyroid

hormone

Note ‑

o Something related to mechanism I requires some explanation.

o Antibody mediated destruction of cells may occur by another process called antibody dependent cellular cytotoxicity (ADCC). Cells that are coated with low doses of Ig G antibody are killed by antibody dependent cytotoxic cells (ADCC) and cell lysis proceeds without phagocytosis. This form of antibody mediated injury does not involve fixation of complement and it is not a type II hyersensitivity.

Ans. is `b’ i.e., Type II Hypersensitivity

  o Myasthenia Gravis is an example of Type II Hypersensitivity reaction.

Ans. is ‘a’ i.e., Blood transfusion reaction

Ans. is ‘b’ i.e., Type 2 hypersensitivity

Ans. A: Steven johnson’s syndrome

Ans. B: Type II hypersensitivity reaction

Type II reactions result when antibody binds to cellular or tissue antigens or to a molecule coupled to a cell or tissue. The antigen-antibody complex activates cells that participate in antibody-dependent cell-mediated cytotoxicity (e.g., NK cells, eosinophils, macrophages), complement, or both.

The result is cell and tissue damage.

Disorders involving type II reactions include hyperacute graft rejection of an organ transplant, Coombs’-positive hemolytic anemias, Hashimoto’s thyroiditis, and anti-glomerular basement membrane disease (e.g., Goodpasture’s syndrome).

Disorders involving type IV reactions include contact dermatitis (e.g., poison ivy), hypersensitivity pneumonitis, Acute transplant rejection, TB, and many forms of drug hypersensitivity.

Chronic graft rejection is type II and type III reaction.

Graft versus host disease is a type IV reaction.

Ans:B.)Type 2

The patient in question is suffering from Myasthenia Gravis

Myasthenia gravis (MG) is a rare autoimmune disorder of neuromuscular transmission in which antibodies form against acetylcholine nicotinic postsynaptic receptors at the neuromuscular junction of skeletal muscles.

Type V hypersensitivity reaction

• This is an additional type that is sometimes (often in the UK) used as a distinction from Type 2.
• Instead of binding to cell surfaces, the antibodies recognise and bind to the cell surface receptors.

Ans. is ‘b’ i.e., Type 2

• Type V hypersensitivity reactions were additionally added to the scheme originally described by Coombs and Gell. Contrary to type IV and in agreement with types I, 11 and III respectively, they are mediated by antibodies too.

The type V reactions are sometimes considered as a subtype of the type II hypersensitivity.

• As its mechanisms do not destroy target cells, they are responsible for induction of organ/tissue dysfunctions only most of authors prefer it to be and independent, the 5′ type of hypersensitivity reactions

Ans. B. Type II hypersensitivity

An example of type II hypersensitivity is the reaction to penicillin wherein the drug can bind to red blood cells, causing them to be recognized as different; B cell proliferation will take place and antibodies to the drug are produced.

Ans:B.)Erythroblastosis Foetalis

Type II hypersensitivity reaction is shown in the image.

Ans. is ‘d’ i.e., Class V