Lecture 14

The country needs DEFENCES because it is under constant threat of attack

The body is also under constant threat of attacks ! • Attacks by bacteria, viruses, fungi, parasites

The body is also under constant threat of attacks ! • Attacks by bacteria, viruses, fungi, parasites • Attack by toxins, poisons • Attack by tumour growth

• So, the body needs DEFENCES too…… • Different defences for different types of invasions

To protect us from these threats, we too have … ….. A Defence System

The Immune System We have Immunity What is immunity? Immunity = State of protection from infectious disease

There are two kinds of immunity Immunity Innate Immunity

Acquired Immunity

Innate Immunity = Non-specific Immunity Natural Immunity Basic resistance that a person is born with, NOT specific to a particular pathogen

Examples of Innate Immune Barriers

Examples of Innate Immune Barriers

Examples of Innate Immune Barriers

Examples of Innate Immune Barriers

Examples of Innate Immune Barriers

Examples of Innate Immune Barriers

Innate Immunity – 4 types of defense barriers 1. Anatomic 2. Physiologic 3. Phagocytic 4. Inflammatory

Innate Immune Barriers 1. Anatomic Barriers SKIN : i. Mechanical barrier against microbes ii. Sweat glands, sebaceous glands Lactic acid, fatty acids

Low pH retards microbial growth MUCOUS MEMBRANES : i. Trap microbes ii. Ciliary movements flush out microbes

Innate Immune Barriers 2. Physiologic Barriers Temperature: Fever inhibits microbial growth Low pH: Acidic pH of stomach kills microbes Chemicals: Lysozyme  lyzes bacterial cell wall Interferon  induces an anti-viral state

IFN prevents viral replication

Innate Immune Barriers 2. Physiologic Barriers Temperature: Fever inhibits microbial growth Low pH: Acidic pH of stomach kills microbes Chemicals: Lysozyme  lyzes bacterial cell wall Interferon  induces an anti-viral state Complement  lysis, chemotaxis, phagocytosis

Innate Immune Barriers 2. Physiologic Barriers Temperature: Fever inhibits microbial growth Low pH: Acidic pH of stomach kills microbes Chemicals: Lysozyme  lyzes bacterial cell wall Interferon  induces an anti-viral state Complement  lysis, chemotaxis, phagocytosis Acute Phase Proteins: C-reactive Protein, CRP  Stimulates complement

Innate Immune Barriers 3. Phagocytic & Endocytic barriers PHAGOCYTOSIS: Uptake by macrophages of particulate material e.g. uptake of bacteria ENDOCYTOSIS: Uptake of material by cells; e.g. fluid droplets, molecules etc

Internalization and elimination / killing

Macrophages are everywhere !

Phagocytosis of bacteria Bacterium being engulfed

Phagocytosis of bacteria Bacterium being engulfed Bacterium inside a vacuole

Phagocytosis of bacteria Bacterium being engulfed Bacterium inside a vacuole Digestion of bacterium begins

Phagocytosis of bacteria Bacterium being engulfed Bacterium inside a vacuole Digestion of bacterium begins

Digestion of bacterium completed

Phagocytosis of bacteria Bacterium being engulfed Bacterium inside a vacuole Digestion of bacterium begins

Digestion of bacterium completed Digested material being exuded

Innate Immune Barriers 4. Inflammatory barriers

Infection  Increase in blood flow  Increase in capillary permeability  Attraction of leukocytes  Migration of leukocytes

Tissue Damage Bacteria Release of factors Extravasation Migration of phagocyte s Complement, antibody

The Summary……….so far Some countries are under constant threat of invasion The body too is under constant threat of invasion

Countries are equipped with defence mechanisms We are also equipped with defence mechanisms e.g. the skin, complement, macrophages etc

Countries have different defence mechanisms to handle different modes of invasion The body is equipped with different innate immune mechanisms to handle different types of “invasions” e.g. Phagocytes eliminate bacteria and viruses in different tissues e.g. Inflammatory reactions help protect against infections in the skin

There are two kinds of immunity Immunity Innate Immunity Acquired Immunity

Acquired Immunity = Specific Immunity = Adaptive Immunity

ACQUIRED IMMUNITY Characteristic Features 1. Specificity – Ability to distinguish pathogens 2. Diversity – Recognize millions of molecules 3. Memory – Faster & stronger second response 4. Self/Non-self Discrimination – Respond to non-self

ACQUIRED IMMUNITY

HUMORAL

B lymphocytes

Antibodies

CELL-MEDIATED

Macrophages, T cells T helper cells T cytotoxic cells

Differences between Innate and Acquired Immunity

Feature

Innate

Acquired

Response Time

Rapid (Minutes/hours)

Slow (Days/weeks)

Specificity

Low

High

Memory

No

Yes

Diversity

Low

Very high

Self non-self discrimination

No

Yes

No.

Date

TOPIC

TUTOR

1

18.9

The Immune System

2

18.9

Organs and Cells of the Immune System

Dr. Raja’a

3

19.9

The Major Histocompatibility Complex

Prof. Raj

4

19.9

Antigens and Antigen Presentation

Prof. Raj

5

20.9

Humoral Immunity

Prof. Raj

6

23.9

Antibody Functions and Complement

Prof. Raj

7

23.9

T cell Receptors and Cell-mediated Immunity

Prof. Raj

8

25.9

Cell-mediated Immunity

Prof. Raj

9

25.9

Cytokines

Prof. Raj

Prof. Raj