Immunology Question discussion topic Infection

1. Topic: IMMUNOLOGY

2. Question 1

3. Explanation
 Microbes that cause disease are called pathogens.
 Infectious diseases are caused by microorganisms such
as viruses, bacteria, fungi or parasites and can spread
between individuals.
 They spread with the help of a vector or a carrier.
 You get an infection when a pathogen enters your body
and begins to multiply.
 Disease occurs when the cells in your body are
damaged as a result of the infection and signs and
symptoms of an illness appear.

4. Question 2

6. Explanation

7. Question 3

8. Explanation
 The living organisms that feed on the dead and
decaying matter is known as saprophytes.
 Unlike parasites, they do not feed on living organisms.
 They break down complex organic matter into simpler
substances that plants can use for a variety of
metabolic activities.
 Saprophytes include fungi and a few bacteria.
 Originating from a Greek word, Saprophytes are
usually referred to as “plant”- the word “phyte” means
plants.
 The role they play in balancing the entire ecosystem
makes them an integral part of soil biology.

10. Question 4

11. Explanation
 A commensal is an organism that uses food supplied in
the internal or external environment of the host,
without establishing a close association with the host,
they do not cause any harm to host.
 The microbes living in harmony with human mostly
consist of bacteria, also known as commensal bacteria.
 These bacteria are present at a particular location of
the body such as the skin surface, oral cavity, intestine,
nasopharyngeal cavity, mucosal surface of the genital
tract, and other anatomical places that provide a
suitable environment for proper growth and
multiplication.

12. Question 5

13. Explanation

16. Question 6

17. Explanation

18. Question 7

19. Explanation
 Many illnesses spread through contact transmission.
 Contact transmission is the most common form of
transmitting diseases and virus.
 There are two types of contact transmission: direct and
indirect.
 Direct contact transmission occurs when there is physical
contact between an infected person and a susceptible
person.
 Indirect contact transmission occurs when there is no
direct human-to-human contact. Contact occurs from a
reservoir to contaminated surfaces or objects, or to vectors
such as mosquitoes, flies, mites, fleas, ticks, rodents or
dogs.
 Respiratory illnesses and sexually transmitted diseases
(STDs) (Eg: Syphilis), diphtheria, pneumonia, cholera,
typhoid, measles, mumps, etc,. are transmitted by direct
contact.

20. Question 8

21. Explanation

22. Question 9

23. Explanation

24. Question 10

25. Explanation

26. Question 11

27. Explanation
 The term heat-labile describes one that is capable of changing or
destruction when subjected to heat.
 Exotoxins are heat-labile proteins, mainly secreted by
Clostridium botulinum, Clostridium tetani, Corynebacterium
diphtheriae, etc.
 Once after the toxins are liberated, it diffuses into the
surrounding medium and causes harm to the host cells either by
disrupting the normal functioning of the cell or by directly
destroying the cells.
 Exotoxins, as the name suggests, are the toxin produced inside
the bacteria itself as a part of their metabolism.
 The endotoxins release the toxins only when the bacteria is
killed, whereas, the exotoxins release toxins immediately into the
environment.
 Exotoxins are more potent and often fatal when compared to
endotoxins.

28. Question 12

29. Explanation
 Pathogens produce toxins which are the major causes of
the infections. These toxins are categorized into two types:
1. Endotoxins 2. Exotoxins
 The endotoxins and exotoxins widely vary in toxicity and
lethality.
 Endotoxin, as the name suggests, is the toxin that is
liberated from the outer cell wall of a bacteria after its
death.
 These toxins are extremely dangerous to the extent that
they can cause severe damage to the organism.
 Endotoxins are produced by Shigella, E.coli, Salmonella,
Pseudomonas, etc.

30. Question 13

31. Explanation
 DNA present in the nucleus is called
nuclear/chromosomal DNA. The DNA molecules
which are present anywhere in the cell, other than
nuclear chromosomes, is called as extranuclear or
extrachromosomal DNA.
 Plasmid is an extrachromosomal circular DNA
molecule present in a prokaryotic cell. This confers
antibiotic resistance to the cell.

32. Question 14

33. Explanation
Bacteremia may not have any symptoms, and your immune system
may clear it on its own. However, if you develop symptoms, you should
see a healthcare provider right away. Without treatment, it can
progress to a severe infection.

34. Question 15

35. Explanation
 Epidemic: The Centers for Disease Control and Prevention
(CDC) describes an epidemic as an unexpected increase in
the number of disease cases in a specific geographical area.
Yellow fever, smallpox, measles, and polio are prime
examples of epidemics.
 Pandemic: The World Health Organization WHO
declares a pandemic when a disease’s growth is
exponential. This means the growth rate skyrockets, and
each day cases grow more than the day prior.
 Endemic: A disease outbreak is endemic when it is
consistently present but limited to a particular region. This
makes the disease spread and rates predictable. Malaria, for
example, is considered endemic in certain countries and
regions.

36. Causes of Disease Outbreaks
Several factors contribute to the outbreak of infectious diseases.
Contraction can occur as a result of transmission from people,
animals, or even the environment.
For example:
1. Weather conditions: For example, whooping cough occurs in
spring, whereas measles tend to appear in the winter season.
2. Exposure to chemicals or radioactive materials. For example,
Minamata is a disease contracted after exposure to mercury.
3. The social aftermath of disasters such as storms, earthquakes,
and droughts can lead to high disease transmission.
4. A number of environmental factors such as water supply, food,
air quality, and sanitation facilities can catalyze the spread of
infectious diseases.

37. Question 16

38. Explanation
 Septicemia, or sepsis, is the clinical name for blood poisoning by
bacteria. It is the body's most extreme response to an infection.
 Sepsis that progresses to septic shock has a death rate as high as
50%, depending on the type of organism involved.
 Without treatment, sepsis can quickly lead to tissue damage,
organ failure, and death.
 Septicemia is dangerous because the bacteria and their toxins
can be carried through the bloodstream to your entire body.
 Sepsis can be divided into three stages: sepsis, severe sepsis and
septic shock. Sepsis: Sepsis is life-threatening. It happens when
your immune system overreacts to an infection. Severe sepsis:
This is when sepsis causes your organs to malfunction. Septic
shock is the last and most severe stage of sepsis.

39. Question 17

40. Explanation
 Epidemic: The Centers for Disease Control and Prevention
(CDC) describes an epidemic as an unexpected increase in
the number of disease cases in a specific geographical area.
Yellow fever, smallpox, measles, and polio are prime
examples of epidemics.
 Pandemic: The World Health Organization WHO
declares a pandemic when a disease’s growth is
exponential. This means the growth rate skyrockets, and
each day cases grow more than the day prior.
 Endemic: A disease outbreak is endemic when it is
consistently present but limited to a particular region. This
makes the disease spread and rates predictable. Malaria, for
example, is considered endemic in certain countries and
regions.

41. Question 18

42. Explanation
 Immunogen and Antigen
 Immunogen is a stimulus that produces a humoral or cell-mediated immune
response, whereas antigens are any substance that binds specifically to an
antibody or a T-cell receptor. All immunogens are antigens, but all antigens
may not be immunogens, some very small molecules called haptens can bind
to antibodies or B-cell receptor but they cannot initiate an immune response.
 Hapten
 Hapten is a molecule that reacts with specific antibody but is not immunogenic
by itself, it can be made immunogenic by conjugation to a suitable carrier.
Many drugs like penicillins are haptens. A hapten is essentially an incomplete
antigen. These small molecules can elicit an immune response only when
attached to a large carrier such as a protein; the carrier typically does not elicit
an immune response by itself.
 Epitope
 An epitope, also known as antigenic determinant, is the part of an antigen that
is recognized by an antibody, B-cell receptor or T-cell receptor. Generally an
antigen has several or many different epitopes and reacts with many different
antibodies, an epitope is approximately five or six amino acids in length.


44. Question 19

45. Explanation

47. Question 20

48. Explanation
 A complete antigen is one that both induces an
immune response and reacts with the products of it,
whereas an incomplete antigen or hapten is unable to
induce an immune response alone but is able to react
with the products of it, e.g., antibodies.
 They produce specific and observable reaction.
 This means that when a complete antigen enters the
body, it can bind to specific antibodies that are
produced by the immune system in response to the
antigen.

49. Question 21

50. Explanation
 An antigen is any substance that causes your immune
system to produce antibodies against it.
 This means your immune system does not recognize
the substance, and is trying to fight it off.
 An antigen may be a substance from the environment,
such as chemicals, bacteria, viruses, or pollen.
 Technically, antigens can be any of the four
macromolecules; proteins, carbohydrates, lipids and
nucleic acids.

51. Question 22

52. Explanation

54. Question 23

55. Explanation

56. Question 24

57. Explanation

59. Question 25

60. Explanation
 In immunology, a paratope, also known as an antigen-
binding site, is the part of an antibody which
recognizes and binds to an antigen.
 It is a small region at the tip of the antibody's antigen-
binding fragment and contains parts of the antibody's
heavy and light chains.

61. Thank You