Human Health and Disease 3 Flashcards
Autoimmune disorder
- Memory-based acquired immunity evolved in higher vertebrates based on
the ability to differentiate foreign organisms (E.g., pathogens) from self cells. - Higher vertebrates can distinguish foreign molecules as well as foreign
organisms. Sometimes, due to genetic and other unknown reasons, the body
attacks self-cells. - This results in damage to the body and is called auto-immune disease.
- Rheumatoid arthritis which affects many people in our society is an auto-
immune disease.
Immune System in the Body
The human immune system consists of lymphoid organs, tissues, cells
and soluble molecules like antibodies. As you have read, immune system
is unique in the sense that it recognises foreign antigens, responds to
these and remembers them. The immune system also plays an important
role in allergic reactions, auto-immune diseases and organ
transplantation.
primary lympohoid organs
Lymphoid organs: These are the organs where origin and/or maturation
and proliferation of lymphocytes occur. The primary lymphoid organs
are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
secondary lymphoid organs
After maturation the
lymphocytes migrate to secondary lymphoid organs like spleen,
lymph nodes, tonsils, Peyer’s patches of small intestine and
appendix. The secondary lymphoid organs provide the sites for
interaction of lymphocytes with the antigen, which then proliferate
to become effector cells.
bone marrow and thymus
The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.
The thymus is a lobed organ located near the heart and beneath the
breastbone. The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size.
Both bone-marrow
and thymus provide micro-environments for the development
and maturation of T-lymphocytes.
i) spleen
ii) lymph nodes
iii) malt
i) The spleen is a large beanshaped organ. It mainly contains lymphocytes and phagocytes.
It acts as a filter of the blood by trapping blood-borne microorganisms. Spleen also has a large reservoir of erythrocytes.
ii)The lymph nodes are small solid structures located at different
points along the lymphatic system. Lymph nodes serve to trap the
micro-organisms or other antigens, which happen to get into the lymph
and tissue fluid. Antigens trapped in the lymph nodes are responsible for
the activation of lymphocytes present there and cause the immune
response.
iii)There is lymphoid tissue also located within the lining of the major
tracts (respiratory, digestive and urogenital tracts) called mucosa-associated lymphoid tissue (MALT). It constitutes about 50 per cent of
the lymphoid tissue in human body.
what is meant by aids
The word AIDS stands for Acquired Immuno Deficiency Syndrome.
This means deficiency of immune system, acquired during the lifetime of
an individual indicating that it is not a congenital disease. ‘Syndrome’
means a group of symptoms. AIDS was first reported in 1981.
AIDS is caused by the Human Immuno deficiency Virus (HIV), a
member of a group of viruses called retrovirus, which have an envelope
enclosing the RNA genome
There is always a time-lag between
the infection and appearance of AIDS symptoms. This period may vary
from a few months to many years (usually 5-10 years).
how is aids transmitted
Transmission of HIV-infection generally occurs by
(a) sexual contact with infected person,
(b) by transfusion of contaminated blood and blood products,
(c) by sharing infected needles as in the case of intravenous drug abusers and
(d) from infected mother to her child through placenta.
people who are at high
risk of getting this infection includes - individuals who have multiple sexual partners, drug addicts who take drugs intravenously, individuals
who require repeated blood transfusions and children born to an HIV
infected mother.
It is important
to note that HIV/AIDS is not spread by mere touch or physical contact; it
spreads only through body fluids.
mechanism of action of hiv
- After getting into the body of the person, the virus enters into macrophages
where RNA genome of the virus replicates to form viral DNA with the help of
the enzyme reverse transcriptase.
-This viral DNA gets incorporated into host
cell’s DNA and directs the infected cells to produce virus particles (Figure 7.6).
The macrophages continue to produce virus and in this way acts like a HIV
factory.
-Simultaneously, HIV enters into helper T-lymphocytes (TH), replicates
and produce progeny viruses.
-The progeny viruses released in the blood attack
other helper T-lymphocytes.
-This is repeated leading to a progressive decrease in the number of helper T-lymphocytes in the body of the infected person.
effects of hiv
- During this period, the person suffers from bouts of fever, diarrhoea and weight
loss.
-Due to decrease in the number of helper T lymphocytes, the person starts
suffering from infections that could have been otherwise overcome such as
those due to bacteria especially Mycobacterium, viruses, fungi and even
parasites like Toxoplasma.
-The patient becomes so immuno-deficient that
he/she is unable to protect himself/herself against these infections. A
how is aids identified
A widely
used diagnostic test for AIDS is enzyme linked immuno-sorbent assay
(ELISA).
Treatment of AIDS with anti-retroviral drugs is only partially effective.
They can only prolong the life of the patient but cannot prevent death, which is
inevitable.
As AIDS has no cure, prevention is the best option.
Moreover, HIV infection, more often, spreads due to conscious behaviour
patterns and is not something that happens inadvertently, like pneumonia
or typhoid. Of course, infection in blood transfusion patients, new-borns
(from mother) etc., may take place due to poor monitoring. The only excuse
may be ignorance and it has been rightly said – “don’t die of ignorance”.
In our country the National AIDS Control Organisation (NACO) and other
non-governmental organisation (NGOs) are doing a lot to educate people
about AIDS. WHO has started a number of programmes to prevent the
spreading of HIV infection. Making blood (from blood banks) safe from
HIV, ensuring the use of only disposable needles and syringes in public
and private hospitals and clinics, free distribution of condoms, controlling
drug abuse, advocating safe sex and promoting regular check-ups for
HIV in susceptible populations, are some such steps taken up.
what is meant by contact inhibition
In our body, cell growth and differentiation is highly controlled and
regulated. In cancer cells, there is breakdown of these regulatory
mechanisms. Normal cells show a property called contact inhibition by
virtue of which contact with other cells inhibits their uncontrolled growth.
what are tumours
Tumour cells/ cancer cells lack the property of contact inhibition. So they divide continuously giving rise to masses of cells called as tumours.
Two types of tumours: benign and malignant
benign tumours
Benign tumors normally
remain confined to their original location and do not spread to other parts
of the body and cause little damage.
