The document discusses the immune system's mechanisms for fighting different types of microbes: - Innate and adaptive immunity work together to fight extracellular bacteria through complement activation, phagocytosis, inflammation, antibodies, and CD4+ T cell activation. Intracellular bacteria are targeted through phagocyte, NK cell, and CD4+/CD8+ T cell activation. Viruses are combated via complement, NK cells, type 1 interferons, antibodies, and CD8+ T cells. - The immune system responds specially to different microbes, though microbes can evade responses. Persistent infections occur when the immune system controls but does not eliminate microbes. - Recent research includes culturing SARS-CoV-2,

1. Immunity to microbes
Submitted to
Dr.Devinder kaur
Submitted by
Gaurav
19mslsbf03

2. Learning Objectives
• Understand the mechanism used by
the immune system to fight with:-
 Extracellular bacteria
 Intracellular bacteria
 Viruses

3. General features of Immune
response to microbes
 Responses always involve innate and adaptive
immunity.
 The immune system responds in distinct and
specialized ways to different type of microbes
to be most effective.
 Microbes evade or resist the effector
mechanism of immunity.
 Many microbes establish latent, or persistent
infections-immune response controls but does
not eliminate the microbe and the microbe
survives without propagating the infection.

4. Immune responses are
specialized for :
 Extracellular bacteria
 Intracellular bacteria
 Viruses
 Fungi
 Parasites

5. Immunity to Extracellular
bacteria
 Innate:
 Complement activation.
 Activation of phagocytes.
 Inflammatory response.
 Adaptive:
Humoral immunity:-
Antibodies block infection
Eliminate microbes
Neutralize toxins
Activation of CD4+
TH cells:-
Enhance phagocytic and microbicidal
activities of macrophages and neutrophils.
Stimulate Antibodies production.

8. Immunity to Intracellular
bacteria
 Innate:
 Activation of phagocytes.
 Activation of NK cells.
 Adaptive:
Activation of CD4+
TH lymphocytes.
 Activation of CD8+
TC lymphocytes.

12. Immunity to Viruses
 Innate:
 Activation of Complement system.
 Activation of NK cells.
Production of Type 1 Interferons(IFN)
 Adaptive:
Humoral Immunity.
 Activation of CD8+
TC lymphocytes (Kill
virus infected cells).

16. Latest Research
• CDC Grows SARS-CoV-2, the virus
that causes COVID-19, in Cell
Culture.
• A Systematic Review on the Efficacy
and Safety of Chloroquine for the
Treatment of COVID-19.
• The Trial of Chloroquine in the
Treatment of Corona Virus Disease
2019 （COVID-19） and Its
Research Progress in Forensic
Toxicology

17. MCQs
Q1.Which of the following substances
will not stimulate an immune
response unless they are bound to a
larger molecule?
a. Antigen
b. Virus
c. Hapten
d. Miligen
e. Antibody
A.Hapten is a small molecule; they can
act as antigen if it binds to a larger
protein molecule. So the answer
is “c”

18. Q2. Which of the following immune
cells/molecules are most effective at
destroying intracellular pathogens?
a. T helper cells
b. B cells
c. Antibodies
d. Complement
e. T cytolytic cells
A. cytolytic cell Tc cells and Natural
killer cells kill infected host cells
which are harboring intracellular
pathogen. So answer is option “e”

19. References:-
(1)
https://web.duke.edu/vaps/BodyDisease/Immunity_to_Mic
robes_Host-Pathogen_Interactions/index5.html
(2)
Kuby Immunology, 8th edition.
(3)
K. Girish., “Microorganisms and their interaction with the
immune system”, Journal of leukocyte biology,1997(62):
415-429.
(4)
https://www.cdc.gov/coronavirus/2019-ncov/about/grows-
virus-cell-culture.html
(5)
https://pubmed.ncbi.nlm.nih.gov/32173110/
(6)
https://pubmed.ncbi.nlm.nih.gov/32212513/