1. By Dr. ShamanthakamaniNarendran Immune System 3. THE
MECHANISMS OF DEFENSE
- All living beings have evolved methods by which they can
protect themselves against microorganisms in their
environment.
- Some operate on the body surface and the mucous membranes,
while others come into play when the deeper tissues are in
danger.
4.
- Skin so long as it is intact acts as a mechanical barrier,
preventing organisms reaching the tissue beneath.
- Mucous membranes like skin, mucous membranes also act as a
mechanical barrier, protecting the deeper tissues.Some of the
secretions (saliva, nasal mucus, and tears) contain enzymes
(lysozyme) which can rapidly kill an invading organism.
5.
- In case organismsdopass through the surface defenses, and reach
the tissues underneath, there are still other powerful defense
mechanisms.
- Defined as theability of the body to recognize, destroy, and
eliminate material foreign to itself .
- This response to an invader occurs as two phases, a primary and
the secondary response.
- The primary response is the way the bodys defense (immune)
system behaves when it encounters an intruder for thefirst time
.
6.
- After a gap of about 3-10 days, specific cells are
activated.
- Depending on the type of intruder the cells either produce
substances to destroy it, or rush to the defense themselves.
- If the alien organism is present in small amounts, the response
does not last more than a week.
- Large amounts of the intruder result in production of defense
weapons called antibodies, which remain in the bloodstream for
several weeks.
7.
- It is now known that both the lymphocytes which go to the
defense themselves (T lymphocytes) and those which produce
antibodies (B lymphocytes) are able to remember an invader,
sometimes for a number of years after the first contact.
- These memory cells thus recognize the invader when it enters
the body the next time.
- This secondary immune response takes place more rapidly than
the primary response.
- The system is already prepared, thus producing a more extensive
response, as well.
8.
- This fact is made use of in immunization programmes, in which
booster doses of weakened forms of the organism are given at
specified intervals.
- In this way, the body is ready to deal with large amounts of
the organism if they enter on their own.
9. Host Defenses Complement system Leuco/ Lymph Macro phage 10.
Allergy Autoimmunity Rejection of organ transplant An immune cell
undergoing an allergic reaction Protects against infectious agents
11.
- The two types of lymphocytes differ in their defense
strategy.
- There are theT lymphocyteswhich undergo further processing in
thethymus .
- Some T lymphocytes are called effecter cells, they directly
kill the intruding organism.
- Others are called controller cells, as they regulate the
activities of the other lymphocytes which are involved in defense
responses.
- Examples of effecter cells include Cytotoxic T cells ,
andNatural killer cells .
12.
- The ways in which these cells destroy an alien organism are
many sometimes they may release substances which break up the cell
membrane of the organism, leading to death.
- Alternatively, other substances may be released which activate
other, migratory cells macrophages .
- These cells engulf and destroy the organism byphagocytosis
.
- The effector T cells defend the body against viruses, they also
attack abnormal or cancerous cells.
13.
- An example of an unwanted response is fighting the tissues of a
transplanted organ.
- This leads to rejection of the transplant.
- Effecter T cells may inactivate and remove an invader the very
first time they are exposed to it.
- There are also memory cells, which can remember an invader and
recognize it, when it next enters the body.
- This memory may last for some years.
- The second response is always more extensive and occurs more
quickly than the first response.
14.
- Controller T cells include Helper T cells and Suppressor T
cells.
- These controller cells influence the activity of other T
cells.
- These controller cells influence the activity of other T cells,
as well as the other category of lymphocytes, called B
lymphocytes.
- These controls are very necessary.
- It is essential that unwanted organisms should be destroyed and
removed without any damage to the body.
15. Themectomy TT given 1.Thymosin fraction V(Calf thymus)
2.Synthetic polypeptides Thymus 16. Ontogeny of Immune System Fetus
T cells Functions at 7- 1/2wks Thymus functions at 12 wks B cells
Functions at 13 wks IgM First to develop.Rises in intrauterine
infection Reaches adult levels by 1 yr IgG Develops at 4 years IgA
At adolescence 17. T cell subpopulation Helper cells (IgA &
IgG) Suppressor (Homeostasis) Killer cells(Kills invading
organisms) B cell subpopulation IgM,IgG, IgA, IgD, & IgE Hay
fever, Asthma, Autoimmune disorder(Hemolytic anemia) 18.
- In case these controls do not function properly, serious
problems arise.
- One extreme may beimmune incompetence , whereas the other
extreme isautoimmunity .
- Inautoimmune disordersthe immune system has started to fight
against the bodys tissues.
19. EosinophilNeutrophil 20.
- TheB lymphocytesare the second type of lymphocytes.
- They are also produced in the bone marrow.
- Unlike the T lymphocytes, their subsequent processing occurs in
lymphoid tissue other than the thymus.
- In birds this occurs in a structure called the Bursa of
Fabricus.
- In man the exact site of processing is not certain it may occur
in lymphoid tissue in the intestine or in the bone marrow.
- When these cells come in contact with an intruder, they get
activated and divide to form cells calledplasma cells .
21. Lymphoid Precursor Cells Liver Bone marrow 22.
Differentiation of lymphoid stem cells T cells (associated with
thymus) B cells(associated with bone marrow) 23. Peripheral
Lymphoid organs Spleen GI tract tissue 24.
- These cells secrete proteins calledantibodies or
immunoglobulins .
- This defense strategy is used to combat many infections.
- Some B lymphocytes survive for many years and remember the
intruder, to recognize it later on.
- The antibodies are specific.
- That is they reach with the same organism which provoked their
production.
- As a result of this specificity, the protection offered is
limited.
25.
- Very often,both T and B lymphocyte immune responses are seen
.
- ThishelperT cells are necessary for the B lymphocytes to be
active.
- Interferon is another important factor in the bodys defense
mechanisms.
26.
- Interferonsare small glycoproteins (protein molecules in
combination with carbohydrate molecules).
- Various agents such as viruses, bacteria, and certain single
cellular organisms trigger theinterferonresponse.
- This mechanism comes into operation before the appearance of
specific antibodies.
27.
- In addition to lymphocytes and interferon, there are
circulating substances in the tissue fluids properdin and
complement .
- These substances cause the wall of the microorganism to break
up, which eventually leads to death of the organism.
28.
- Like autoimmune disorders, are conditions in which the property
of the immune system as a defense system is modified.
- These defenses are activated by substances which are not
actually harmful.
- These allergy producing substances are all around us.
- Harmless substances in the air we breathe dust, pollen; in our
food and drink, in the clothes we wear, and the things we
touch.
29. THE ALLERGIC RESPONSE allergen IgE release of histamine
ALLERGIC REACTION Mast cell 30. PSYCHONEUROIMMUNOLOGY (BRAIN +
IMMUNE SYSTEM)
- In recent years there has been a growing awareness that the way
we feel can influence out bodys immune mechanisms.
- This suggests that there are connections between the nervous
and the immune system.
- This was apparent from an observation that just before an exam
a larger number of school children were likely to suffer from
(genuine!) sore throats compared to the rest of the year.
31.
- Another observation was that just a period of extreme grief
(e.g. the death of a close relative) there was a greater incidence
of developing one of the most severe diseases cancer.
- This can also be linked with the immune system an efficient
immune system should be able to detect a cancer cell and eliminate
it before it has the chance to spread.
- These observations lead to a great deal of interest and
speculations.
32. PSYCHONEUROIMMUNOLOGY (BRAIN + IMMUNE SYSTEM) killer cells
sudden stress increased killer cells reduced killer cells repeated
stress 33. Diseases due to Immunologic deficiency Primary Secondary
34. AIDS Acquired immunodeficiency syndrome Pathophysiology
Clinical diagnosis Treatment Prevention HIV, the virus that causes
AIDS, is shown budding out of a human immune cell. 35. HIV Treating
HIV infected woman during pregnancy Natural history of HIV
infection Transmission Signs and symptoms of AIDS in new born How
does pediatric AIDS differ from adult AIDS Management &
Specific retroviral therapies AZT (3 Azido, 2 3 deoxythymdine) DDI
(2 3 Dideoxyinosine) Immunotherapy (Hyposensitization)