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Immune System

Description: This test will help the learning students to revise the topic thoroughly.
Number of Questions: 15
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Tags: Immune system The Defence Mechanism Immune System of Human Body
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The mononuclear phagocyte system does not include which one of the following?

  1. Monocytes

  2. Kupffer cells

  3. Kidney mesangial cells

  4. Lymph node medullary macrophages

  5. Endothelial cells


Correct Option: E
Explanation:

Endothelial cells are not essentially phagocytic, although they do contribute in the production of mediators of the inflammatory process, particularly acute inflammation and were previously lumped together with the mononuclear phagocyte system in what was known as the reticuloendothelial system (RES).

Polymorphonuclear neutrophils (PMNs) are the most abundant circulating blood leucocytes providing the first-line of defense against infection. Which of the following statements is true for Polymorphonuclear neutrophil (PMN)?

  1. It is a bone marrow stem cell.

  2. It is closely similar to a mast cell.

  3. It contains microbicidal cytoplasmic granules.

  4. It is not a professional phagocytic cell.

  5. It has granules which stain with eosin.


Correct Option: C
Explanation:

The granules contain a wide spectrum of microbicidal agents.

Which of the following does not protect any body surface?

  1. Skin

  2. Mucus

  3. Gastric acid

  4. Salivary amylase

  5. Gut microflora


Correct Option: D
Explanation:

The enzyme splits starch and is important for digestion, but not for protection.

Defensins are small cysteine-rich cationic proteins found in humans. Neutrophil defensins are

  1. anti-toxins

  2. peptide antibiotics

  3. oxygen-dependent

  4. enzymes

  5. glycolipids


Correct Option: B
Explanation:

The defensins are peptide antibiotics present in the granules in extremely high concentration.

Toll-like receptor 9 is a protein found in human beings encoded by the TLR9 gene. The TLR9 pattern recognition receptor recognises

  1. the CpG motifs

  2. gram +ve peptidoglycan

  3. mycobacterial lipoarabinomannan

  4. gram –ve LPS

  5. dsRNA


Correct Option: A
Explanation:

Toll-like receptor 9 recognition of these microbial dinucleotide sequences leads to activation of the NFkB transcription factor.

Acute inflammation in a body characteristically involves

  1. constriction of arterioles

  2. capillary endothelial cell enlargement

  3. influx of macrophages

  4. influx of mast cells

  5. influx of neutrophils


Correct Option: E
Explanation:

Neutrophils are chemotactically attracted to the site of inflammation by C5 a and mast cell chemotactic factors such as leukotriene B4.

Natural killer cells are a type of lymphocyte and a component of innate immune system. Natural killer (NK) cells do not

  1. respond to interferon

  2. contain perforin

  3. contain tumor necrosis factor (TNF)

  4. kill only by damaging the target cell outer membrane

  5. contain serine proteases


Correct Option: D
Explanation:

Perforin inserts into the target cell membrane, thereby facilitating entry of TNF and granzymes into the target cell.

Which of the following is not an acute phase protein in human beings?

  1. Serum amyloid P component

  2. Chondroitin sulphate

  3. C-reactive protein

  4. Mannose binding lectin

  5. Fibrinogen


Correct Option: B
Explanation:

Chondroitin sulphate is a molecule that is found naturally in the body. It has mostly been used to treat joint disorders such as osteoarthritis. This is a cell matrix component.

Which among the following statements regarding interferons is correct?

  1. They are found only in mammalian species.

  2. They are divided into 5 main families.

  3. They induce enzyme synthesis in the target cell.

  4. They only affect infected cells.

  5. They are specific for individual viruses.


Correct Option: C
Explanation:

Derepression of genes in the target cell results in the synthesis of a protein, kinase and an endonuclease.

Pattern recognition receptors are expressed by innate immune cells and are essential for detecting invading pathogens. Which of the following do they include?

  1. LPS

  2. PAMPs

  3. Lipoteichoic acid

  4. Lectin-like molecues

  5. Unmethylated CpG sequences


Correct Option: D
Explanation:

Many PRR are lectin-like, they recognise exposed microbial sugars.

Complement component 3 is a prominent protein of the immune system contributing to the innate immunity. It is cleaved by

  1. C3b

  2. C3bBb

  3. Factor B

  4. Factor D

  5. Factor H


Correct Option: B
Explanation:

This is the C3 convertase enzyme generated in the alternative complement pathway and is responsible for splitting the small peptide C3a, leaving C3b as a residue.

The membrane attack complex is a type of two-stage immune response to the threats to the body. It consists of which of the following?

  1. OH

  2. Colicins

  3. C3b3b, Bb

  4. C5b, 6, 7, 8, 9

  5. Properdin


Correct Option: D
Explanation:

These terminal components form a complex, which inserts into the membrane to form a transmembrane ion channel that leads to lysis of the cell.

Polymorphonuclear neutrophils attack bacteria

  1. by phagocytosis

  2. exclusively by oxygen-dependent mechanisms

  3. exclusively by oxygen-independent mechanisms

  4. by secreting complement

  5. by secreting interferon


Correct Option: A
Explanation:

The ability to ingest bacteria and killing them is a major feature of these professional phagocytic cells. Loss of neutrophils renders the host very susceptible to overwhelming infection.

Acute inflammation can be initiated by

  1. lysosyme

  2. influx of neutrophils

  3. an increase in vascular permeability

  4. C3

  5. mast cell activation


Correct Option: E
Explanation:

Activation of mast cells releases chemotactic factors for neutrophils and vasoactive mediators such as histamine.

Complement component is placed on microbes to destroy them. Several of the complement components are

  1. glycolipids

  2. cytokines

  3. enzymes

  4. hormones

  5. antibodies


Correct Option: C
Explanation:

They act in a sequential proteolytic cascade, which gives tremendous amplification of the response.

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