This document discusses immunity, including innate immunity present at birth and acquired immunity developed during life through exposure to pathogens. Innate immunity provides non-specific resistance and includes mechanical barriers, secretions, cellular factors, fever and inflammation. Acquired immunity is either active (developed from natural infection or vaccination) or passive (from transfer of antibodies). Active immunity induces antibody production and cellular responses, providing durable protection. Passive immunity transfers pre-formed antibodies, offering short-term protection until the antibodies degrade.

1. IMMUNITY
IMMUNITY refers to resistance of a host
to pathogens and their toxic products
The IMMUNE SYSTEM is also
concerned with reaction against any
foreign antigen
HYPERSENSITIVITY refers to the
injury caused to the host by the
immune system

3. INNATE IMMUNITY
• Present at birth
• Due to genetic and
constitutional make up
• Not affected by repeated
contact with organism
• Non specific- meaning a
degree of resistance to all
organisms in general
• Specific-when referring to a
particular pathogen

4. INNATE IMMUNITY
Species immunity
Racial immunity
Individual immunity

5. SPECIES IMMUNITY
• Due to biologic and
biochemical
differences in the
tissues of different
host species
• Frogs:35 degrees C
= anthrax

6. RACIAL IMMUNITY genetic
due to selection
Algerian sheep European sheep
Anthrax

7. Racial immunity cont.
• Tuberculosis?

8. INDIVIDUAL IMMUNITY
Similar degree of resistance ?

9. Factors influencing innate
immunity
• Age
• Hormonal influences and
Gender
• Nutritional factors

10. AGE
FETUS-immature immune system-
congenital infection Toxoplasma,
Rubella, CMV, Herpes, HEP B
NEW BORN more susceptible to
infection
Coxksakie infection is fatal in suckling
suckling mice.

11. CHILDREN- Tenia capitis
PREPUBERTAL GIRLS-
vaginal gonococcal infection
ADULTS-polio ,chicken pox
ELDERLY-more susceptible to
pneumonia, urinary tract infection

12. HORMONAL INFLUENCES
DIABETICS have more
pyogenic and fungal infections
STEROIDS: depress host
resistance by lower antibody
and anti -phagocytic action but
they also have toxin neutralising
and anti- inflammatory action
PREGNANCY and STRESS
HYPOTHYROIDISM and
ADRENAL DYSFUNCTION
In such conditions INFECTIONS
are common

13. NUTRITIONAL FACTORS
IMMUNITY IS REDUCED
-MALARIA,VIRAL
INFECTION.
Obesity and
diabetes

14. MECHANISM OF INNATE
IMMUNITY
• Mechanical barriers and secretions
• Anti bacterial substances in
blood/tissues
• Microbial antagonism
• Cellular factors
• Fever
• Inflammation
• Acute phase proteins

15. Mechanical barriers and surface
secretions

16. EPITHELIAL SURFACES
SKIN-salt in sweat, sebaceous secretions
and long chain fatty acids show
bactericidal action on transient flora.
People immersing hands in soapy water
continually - get fungal infections.
Skin has resident flora not
removed by washing

17. RESPIRATORY TRACT
NOSE prevents entry of large particles with
microorganisms near nasal orifices
MUCUS on the epithelium sweeps particles into
pharynx by the cilia - swallowed or coughed
Sneeze and cough reflex
NASAL SECRETIONS have muco-
polysaccharides attaching
to viruses
ALVEOLI –phagocytic cells

18. GASTROINTESTINAL TRACT
MOUTH saliva inhibits many micro organisms
STOMACH acid with Ph 4
ILEUM & LARGE INTESTINE varied flora
MUCUS in intestine entangles particles and
propels them
forward

19. CONJUNCTIVA tears contain lysozyme-
acts as a muraminidase, destroying bacteria. Tears
also flush the cojunctival sac of dust
URINE flushing eliminates bacteria
SEMEN spermine and zinc (bactericidal)
ADULT VAGINA aciduric bacteria (lactobacilli)
ferment glycogen in lining cells and prevent
infection.

20. BLOOD AND TISSUES
• COMPLEMENT- destroys pathogenic
bacteria
• BETA LYSIN acts on anthrax and others
bacteria
• LEUKINS and PLAKINS
• LACTIC ACID in muscle and
inflammatory areas
• LACTOPEROXIDASE in milk

21. MICROBIAL ANTAGONISM
RESIDENT FLORA OF SKIN/ MUCOSA
prevent colonisation by pathogenic microbes
ALTERATION of resident bacteria in GIT may
cause Staphyloccal or Clostridial
Enterocolitis after oral antibiotics
GERM FREE ANIMALS are very susceptible to
infection (gnotobiotes)

22. Humoral and cellular defence
mechanisms

23. CELLULAR FACTORS
• PHAGOCYTES (Metchnikoff 1883) are
classified into:
• Microphages - polymorphs
• Macrophages - histiocytes, fixed RE cells
and monocytes
FUNCTION: removal of foreign cells by
phagocytosis but capsulate bacteria require
opsonisation
Brucella and lepra bacilli survive in the cells
and can spread in the body
• NATURAL KILLER CELLS defend against
virus-infected and cancer cells

24. PHAGOCYTOSIS

26. Inflammatory Response
Non specific mechanism
Arterioles constrict and then dilate causing
increased and slow blood flow
WBC engulf and digest the organisms
Outpouring of plasma dilutes the toxins
Fibrin barrier walls off the site

27. FEVER
Natural defense
mechanism to hasten the
physiologic process ; may
may also kill organisms eg-
in Syphilis
FEVER stimulates
production of INTERFERON
-active against virus
infection

28. ACUTE PHASE PROTEINS
• C reactive protein ,
• mannose binding protein,
• alpha 1 glycoprotein are a few of them
• They :activate the alternate pathway
• of complement
• :increase resistance,
• :prevent tissue injury
• :promote repair after inflammation

29. ACQUIRED IMMUNITY
The resistance acquired by an individual during
life is called specific immunity or
ACQUIRED IMMUNITY
Active immunity Passive immunity
Artificial Artificial
Natural Natural

30. ACTIVE/ADAPTIVE PASSIVE
Produced by host immune system Received from outside
Durable protection-depending on the
pathogen
Transient-days to months
Induced by pathogen /antigenic stimulus Ready made
Lag period present No lag period
Immunologic memory present No immunologic memory
Booster effect on repeat administration Less effective on repeat administration
Negative phase may occur No negative phase
Not applicable in immunodeficiency Applicable in immunodeficiency
More effective than passive immunization Inferior to active immunization

31. ACTIVE IMMUNITY
• Resistance induced in an individual
after effective contact with an antigen
• Either following
:Natural infection
:Vaccination.
• Response of body:
• : Humoral
• : Cell mediated

32. NATURAL ACTIVE IMMUNITY
• Response to clinical /inapparent infection
• Duration of Immunity in virus infections:
Lifelong in chicken pox or measles infection
• Short -in influenza due to antigenic variation
and in common cold due to many types of
rhino viruses
• Adults may have natural active immunity to
polio due to in-apparent infection

33. Bacterial infections: immunity is less
permanent
No effective immunity in chancroid
(Haemophillus ducreyi)
Durable protection in typhoid
Premunition- In syphilis immunity to
reinfection lasts as long as the original
infection is active

34. ACTIVE IMMUNITY
HUMORAL CELL MEDIATED
B CELL/ PLASMA CELL T CELLS
ANTIBODIES

35. ARTIFICIAL ACTIVE IMMUNITY
BACTERIAL VACCINES-
Live: BCG for tuberculosis
Killed: cholera, TAB (typhoid)
Subunit: typhoid Vi antigen
Bacterial product: tetanus toxoid
VIRAL VACCINES:
Live :Sabin (oral polio)
Killed: Salk (parentral polio)
Subunit: Hepatitis B vaccine

36. VACCINES

37. PASSIVE IMMUNITY
• Resistance offered to an individual by the
transfer of preformed antibodies (ready-
made from another person/animal) against
an infective agent or toxin.
The immune system of the individual plays
no active role and the protection comes into
effect immediately
• Protection is short lasting – days or weeks
and useful in instant immunity

38. NATURAL PASSIVE IMMUNITY
Immunity passed from mother to fetus:
Through placenta- Ig G
Through colostrum - Ig A
Active IMMUNISATION of MOTHER in
pregnancy increases passive immunity
in infants- tetanus, Hep A, Hep B,
inactivated influenza, Td.

39. ARTIFICIAL PASSIVE IMMUNITY
Hyper-immune serum of human/animal
Convalescent sera, pooled gamma globulin
of humans (half life 26 d, effect lasts for 3m)
Animal sera is the oldest method, not preferred
nowadays due to hypersensitive reactions
Animal sera still used - gas gangrene, botulism
and snake bite (large amts can be prepared but
it is a foreign protein)
Serum should be administered IM not IV
IV administration causes aggregation of
Immuno -globulin molecules and anaphylaxis

40. Antisera for Immunisation

41. USES OF ANTISERA
Protects non- immune host so they are used in
treatment of infections
Used for suppression of active immunity in Rh iso-
immunization
POOLED human immunoglobulin from sera of
healthy adult donors contains antibodies used to
boost immunoglobulin levels in children with hypo-
gamma globulinemia against measles and hepatitis
Antisera from human source should be free from HIV,
HepB, HepC

42. LOCAL IMMUNITY - Besredka (1919-24)
Gut immunity in polio (Sabin vac.) oral cholera
vaccine and Typhoral (typhoid)
Intra-nasal vaccine –influenza (live)
Protected by local secretory Ig A
HERD IMMUNITY: Over-all level of immunity in a
community is useful in control /prevn. of epidemics.
If a large proportion of the herd/ population(80%) is
immune, the herd immunity (which is more important
than individual immunity) is satisfactory and helpful in
eradication of diseases