IMMUNITY
BY
DR.MUHAMMAD KHALID
What Is Immunity
Immunity is the ability of the body
to specifically counteract foreign
organisms or substances, called
antigens.
Antigen -- foreign compounds which
initiate an immune response
Antibody -- proteins produced by B
lymphocytes which attack antigens
What Is Immune System
The immune system is the system
of specialized cells and organs that
protect an organism from outside
biological and chemical influences.
Organs of the Immune System:
1:Primary organs:
Thymus: Responsible for maturation of the T cells. Bone
Marrow: Responsible for maturation of B cells.
2: Secondary organs:
- Spleen
-Lymphatic system
-Highly organized follicles are present in small intestine
(Peyerís patches) and tonsils
-Mucosal-Associated Lymphoid Tissue
-Specialized M-cell in wall of mucus membrane entraps foreign
particle
 INNATE IMMUNITY:
- faster-acting
- non-specific
- no stimulation needed for activation
- It is genetically based and we pass it
on to our offspring.
- present from birth
- active round the clock
-First-line defenses:
1: physical and chemical barrier – skin and mucus
coating of the gut and airways
2: the stomach secretes gastric acid
-Second-line defense: Phagocytic cells:
1: phagocytic cells ( macrophages and
neutrophil granulocytes) that can engulf
(phagocytose)
2: Phagocytosis involves chemotaxis –
chemotactic chemicals – adhesion -by
opsonization, opsonins-ingestion-reactive
oxygen species and proteases
- Anti-microbial proteins:
-several classes of antimicrobial proteins
a: acute phase proteins (C-reactive protein)
b: lysozyme, and the complement system
c: The complement system is a very complex group
of serum proteins
- interferons - secreted by virus-infected cells
 ACQUIRED IMMUNITY
-adaptive immune system
-ensure full/partial immunity against
reinfection by the same organism
-based on specialized cells called
lymphocytes ,produced by stem cells
in the bone marrow
-Lymphocytes - two major types: B
cells and T cells.
- Roughly 80% of them are T cells,
- 15% B cells and
- 5%rest are null Lymphocytes.
- B cells produce plasma cells which
then produce antibodies
- T cells become T helper (CD4) or
cytotoxic (CD8) lymphocytes
- If acquired immunity is due to B cells
or antibodies (IgA,IgG,IgM,IgD and
IgE) it is also called Humoral
immunity.
- If acquired immunity is due to T cells
it is also called Cellular immunity
Antibody isotypes of mammals
Name Types
IgA
IgD
IgE
IgG
IgM
Description
2
Found in mucosal areas, such as the gut, respiratory tract and
urogenital tract, and prevents colonization by pathogens.[10] Also
found in saliva, tears, and breast milk.
1
Functions mainly as an antigen receptor on B cells that have not
been exposed to antigens.[11] It has been shown to activate
basophils and mast cells to produce antimicrobial factors.[12]
1
Binds to allergens and triggers histamine release from mast cells
and basophils, and is involved in allergy. Also protects against
parasitic worms.[6]
4
In its four forms, provides the majority of antibody-based
immunity against invading pathogens.[6] The only antibody
capable of crossing the placenta to give passive immunity to
fetus.
1
Expressed on the surface of B cells and in a secreted form with
very high avidity. Eliminates pathogens in the early stages of B
cell mediated (humoral) immunity before there is sufficient
IgG.[6][11]
Antibody Complexes
Acquired Immunity
A. Is either active or passive
B. either , naturally acquired or
artificially acquired
Active acquired immunity
- Long-lasting (usually life-long)
- Develops after exposure to antigen
- the body manufactures antibodies
or sensitized lymphocytes itself
– actively
1.(NATURALLY ACQUIRED ACTIVE IMMUNITY)
The exposure may occur "naturally"
a) It is accidental: the host unintentionally comes in
contact with the antigen
b) Naturally acquired diseases and infections
(1)
primary antibody response
IgM appear first followed much later by IgG
(2) secondary antibody response
IgG is produced in high concentrations as a
result of memory cell formation
2. (ARTIFICIALLY ACQUIRED ACTIVE IMMUNITY)
The exposure may occur artificially
a)
It is deliberate and planned
b)
That is, the host is intentionally exposed to the antigen
c)
For example, the infant (or adult) receives
immunizations at the doctor's office
The individual undergoes a primary and secondary
antibody response
Passive acquired immunity
1.
2.
3.
4.
5.
Is short-lasting
Is a "gift" of antibodies produced
outside the host's body
Mother to newborn
Emergency – ATS , ARG
Protection for sometime until
active immunity develops
1. This acquisition of antibodies may occur "naturally"
(NATURALLY ACQUIRED PASSIVE IMMUNITY)
a)
also known as congenital immunity
b)
maternal antibodies transferring to the fetus
through the placenta - IgG
c)
maternal antibodies transferring to baby
through mother's milk -IgA, with trace amounts
of IgG and IgM
2.This acquisition of antibodies may occur
"artificially" (ARTIFICIALLY ACQUIRED PASSIVE
IMMUNITY)
a)
This occurs as a result of antibodies to a particular
antigen being deliberately injected into the host
b)
antiserum – ATS, ARabiesS , Antidiptheria serum
c)
Gamma globulins – ATG, Gamma immune, ARG
APPLICATIONS OF
IMMUNITY:
-Serology is the use of laboratory tests to detect
antigen and antibody reactions to diagnose infections
or do many other tests
-Herd immunity
- Vaccination
-active artificial immunity
IMMUNE DISORDERS:
Attenuated Or Low Response:
HIV,Steroids,Malnutrition,
pregnancy
Exaggerated Response :
Autoimmune disorders,
IDDM,RA,SLE,drug reactions,
THANKS