Acute inflammation- cellular events

Acute inflammation- cellular events

Q. 1

The process of phagocytosis was discovered by:

 A

Virchow

 B

Metchnikoff

 C

Koch

 D

None of the above

Q. 1

The process of phagocytosis was discovered by:

 A

Virchow

 B

Metchnikoff

 C

Koch

 D

None of the above

Ans. B

Explanation:

In the 1880s the Russian biologist Elie Metchnikoff discovered the process of phagocytosis by observing the ingestion of rose thorns by amebocytes of starfish larvae and of bacteria by mammalian leukocytes.
Ref: Robbins 8th edition, Chapter 2.

Q. 2

During phagocytosis, the metabolic process called respiratory burst involves the activation of:

 A

Oxidase

 B

Hydrolase

 C

Peroxidase

 D

Dehydrogenase

Q. 2

During phagocytosis, the metabolic process called respiratory burst involves the activation of:

 A

Oxidase

 B

Hydrolase

 C

Peroxidase

 D

Dehydrogenase

Ans. A

Explanation:

During phagocytosis, NADPH oxidase and myeloperoxidase work together in killing bacteria. NADPH oxidase, located in the leukocyte cell membrane gets activated and reduces oxygen from the surrounding tissues to superoxide. This is known as the “respiratory burst”.

Ref: Illustrated Reviews: Biochemistry By Lippincott, 5th Edition, Chapter 13, Page 148; Nutritional Biochemistry of The Vitamins By David A. Bender, 2nd Edition, Chapter 7, Pages 187-88.

Q. 3

The process increasing the ability for phagocytosis of foreign bodies by body is called ‑

 A

Cross reactivity

 B

Opsonisation

 C

Immune Tolerance

 D

Immune Surveillance

Q. 3

The process increasing the ability for phagocytosis of foreign bodies by body is called ‑

 A

Cross reactivity

 B

Opsonisation

 C

Immune Tolerance

 D

Immune Surveillance

Ans. B

Explanation:

Ans. is ‘b’ i.e., Opsonisation

Opsonization

.   The coating of an antigen or particle (eg. infectious agent) by substances such as antibodies, complement components and fibronectin facilitate phagocytosis.

.   Opsonization can occur by three mechanisms :

  1. Antibody alone acts as opsonin
  2. Antibody plus antigen can activate complement via classical pathway to yield opsonin.
  3. Opsonin may be produced by a heat labile system in which immunoglobulin or other factors activate C3 via alternative pathway.

Opsonin

.   A substance capable of enhancing phagocytosis.

Antibodies and complement are the two main opsonins.

About other options:

Cross reactivity

Some times single antigen stimulates production of variety of antibodies that more or less resemble the correct fit for the antigen. Each of these antibodies may attack different antigens that more or less resemble one another. This is known as antigen cross reactivity.

.   Immunological tolerance

Immunological tolerance is the condition in which contact with an antigen specifically abolishes the capacity to mount an immune response against that particular antigen when it is administered subsequently.

Immunological surveillance

It is the process by which cell mediated immunity destroys malignant cells that arise by somatic mutation.



Q. 4

Bacteria coated with complement and Ig; phagocytosis is enhanced by- 

 A

Receptor mediated endocytosis

 B

Pseudopod formation

 C

Myeloperoxidase mediated destruction

 D

C3b – Fc mediated destruction

Q. 4

Bacteria coated with complement and Ig; phagocytosis is enhanced by- 

 A

Receptor mediated endocytosis

 B

Pseudopod formation

 C

Myeloperoxidase mediated destruction

 D

C3b – Fc mediated destruction

Ans. D

Explanation:

Ans. is ‘d’ i.e., C3b- Fc mediated destruction

  • Here, the examiner is simply asking about the opsonization. Complement (especially C3b) and Ig coating the bacteria act as opsonin and enhance phagocytosis.
  • The speed of phagocytosis can be increased markedly by bringing into action two attachment devices present on the surface of phagocytic cells

:‑

i)        Fe receptor :- which binds the Fc portion of antibody molecule, chiefly IgG

ii)      Complement receptor (CR3) :- which binds the third component of complement especially C3b.

  • This coating of the organisms by molecules that speed up phagocytosis, is termed `opsonization’ and the Fc portion of antibody and C3b are termed as opsonins.

Now the question crops, how does opsonins enhance phagocytosis : ‑

  • Both the membrane of a phagocytosing cell and its target have a negative charge (zeta-potential), making it difficult for the two cells to come close together. Once the opsonins attach to the target, the negative charged is masked. Take note that the negative charge of the target doesn’t disappear. The opsonin simply overrides the charge, making it easier for white blood cells (phagocytic cells), to undergo phagocytosis. During the process of opsonization (also, opsonisation), antigens are bound by antibody or complement molecules. Phagocytic cells express receptors, CR1 and Fc receptors, that bind opsonin molecules, C3b and antibody, respectively. With the antigen coated in these molecules, binding of the antigen to the phagocyte is greatly enhanced. In fact, most phagocytic binding cannot occur without opsonization of the antigen.
  • Furthermore, opsonization of the antigen and subsequent binding to an activated phagocyte will cause increased expression of complement receptors on neighboring phagocytes.

About option c

  • As you all know, inside the phagocytes, bacteria are destroyed by lysosomal enzymes (lactoferrin, lysozyme
    defensins) and reactive oxygen intermediate (myeloperoxidase system, superoxide, H202, hydroxy radicals).
  • However, this process has nothing to do with opsonins. Opsonins enhance phagocytosis by masking the negative charge on the bacterium so that it easily comes in contact with phagoctes.

Quiz In Between


Q. 5

Phagocytosis enhanced by coating the surface of antigen is called –

 A

Opsonisation

 B

Chemotaxis

 C

Decoding

 D

CFT

Q. 5

Phagocytosis enhanced by coating the surface of antigen is called –

 A

Opsonisation

 B

Chemotaxis

 C

Decoding

 D

CFT

Ans. A

Explanation:

Ans. is ‘a’ i.e., Opsonisation


Q. 6

Phagocytosis is not done by –

 A

NK cells

 B

Histiocytes

 C

WBC

 D

Macrophages

Q. 6

Phagocytosis is not done by –

 A

NK cells

 B

Histiocytes

 C

WBC

 D

Macrophages

Ans. A

Explanation:

Ans. is ‘a’ i.e., NK cells


Q. 7

All of the following vascular changes are observed in acute inflammation, except –

 A

Vasodilation

 B

Stasis of blood

 C

Increased vascular permeability

 D

Decreased hydrostatic pressure

Q. 7

All of the following vascular changes are observed in acute inflammation, except –

 A

Vasodilation

 B

Stasis of blood

 C

Increased vascular permeability

 D

Decreased hydrostatic pressure

Ans. D

Explanation:

Ans. is d i.e., Decreased hydrostatic pressure

Quiz In Between



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